Scientific Studies Database By Natural Foundation

We've collected over 1000 studies on the products we sell. We've compiled the most interesting studies on this page.

We stay on top of the latest scientific research to ensure our products are as effective and safe as possible.

Tongkat Ali Scientific Studies

Numerous clinical trials have investigated the effects of tongkat ali in humans over the past 20 years. We have summarised some of the most important studies related to testosterone, sexual function, stress and energy.

Study 1

Study type: 

Clinical trial (double-blind, placebo-controlled)

Dose:

600 mg/day of Tongkat Ali with 1.45% eurycomanone

Participants:

32 men aged from 20 to 30  

Duration:

2 weeks

Results:

The researchers observed steroidogenic effects after Tongkat Ali supplementation. No adverse side effects were observed. 

600mg/day was correlated with significant increases in testosterone (15%), free testosterone (34%) and estrogen (30%) levels. The testosterone level was raised slightly above the normal human range. The authors concluded that 600mg/day of Tongkat Ali could have a positive impact on sports performance.

Link:

https://doi.org/10.1111/and.14001

Study 2

Study type: 

Randomised, double-blind, placebo-controlled trial

Dose:

50mg of Tongkat Ali per day

Additional interventions:

Multivitamin mix

Participants:

95 men and women aged from 25 to 65

Duration:

24 weeks

Results:

Tongkat Ali supplementation was associated with significant increases in free testosterone. Males experienced a 682% average increase in free testosterone. Females experienced a 700% average increase in free testosterone.

Year:

2018

Link:

https://doi.org/10.29219/fnr.v62.1374  

Study 3

Study type: 

Randomised, double-blind, placebo-controlled trial

Dose:

100mg or 200mg of Tongkat Ali per day

Participants:

106 males aged from 50 to 70 with low testosterone

Duration:

12 weeks

Results:

Tongkat ali supplementation was associated with significant increases in total testosterone. A dose of 200mg per day was associated with a 12.2% increase in total testosterone and a 16.9% increase in free testosterone. 

Year:

2021

Link:

https://doi.org/10.29219/fnr.v65.5647 

Study 4

Study type: 

Randomised double-blind placebo-controlled trial

Dose:

200mg of Tongkat Ali per day 

Additional interventions:

3 hour-long training sessions per week

Participants:

45 middle-aged, androgen-deficient males

Duration:

6 months (the longest trial of tongkat ali supplementation to date)

Results:

Tongkat Ali supplementation was associated with increases in total testosterone levels and improvements in erectile function.

Year:

2020

Link:

https://doi.org/10.1016/j.maturitas.2020.12.002 

Study 5

Study type: 

Randomised, double-blind, placebo-controlled trial

Dose:

200mg of Tongkat Ali per day

Participants:

26 men aged from 45 to 60 with mild erectile dysfunction

Duration:

12 weeks

Results:

Tongkat Ali supplementation was associated with a 36% increase in total testosterone. No adverse effects were observed; liver and kidney values showed no significant changes from baseline.

Link:

https://doi.org/10.1155/2014/179529

Study 6

Study type: 

Randomised, double-blind, placebo-controlled trial

Dose:

200mg of Tongkat Ali per day

Participants:

32 men and 31 women experiencing moderate stress

Duration:

4 weeks

Results:

Tongkat Ali supplementation was associated with a 37% increase in testosterone and an improved cortisol:testosterone ratio.

Link:

https://doi.org/10.1186/1550-2783-10-28

STUDY 7

Study type: 

Randomised, double-blind, placebo-controlled trial

Dose:

200mg, 400mg and 600mg of Tongkat Ali per day

Participants:

20 healthy males aged from 38 to 58  

Duration:

2 months

Results:

Testosterone levels increased after 3 weeks of Tongkat Ali supplementation. The high dose of 600mg/d did not adversely affect liver function, renal function, blood profiles, electrolytes, cancer markers and the immune system.

Link:

https://www.researchgate.net/publication/295384337_Standardized_watersoluble_extract_of_eurycoma_longifolia_LJ100_on_men's_health 

Study 8

Study type: 

Systematic review and meta-analysis

Studies:

9 studies in the systematic review and 5 studies in the meta-analysis

Results:

The systematic review revealed that most studies reported a significant improvement in total testosterone levels after Tongkat Ali supplementation. The meta-analysis suggested that Tongkat Ali could improve testosterone production.

Link:

https://doi.org/10.3390/medicina58081047

Study 9

Study type: 

Uncontrolled trial

Dose:

200mg of Tongkat Ali per day

Participants:

76 men with hypogonadism

Duration:

4 weeks

Results:

Tongkat Ali supplementation was associated with a 46.6% average increase in serum testosterone concentrations (from 5.66 nM to 8.3 nM). The participants also experienced improvements in erectile function and libido.

Link:

https://doi.org/10.1111/j.1439-0272.2011.01168.x

Study 10

Study type: 

Uncontrolled trial

Dose:

200mg of Tongkat Ali per day

Participants:

13 physically active males and 12 physically active females aged 57 to 72

Duration:

5 weeks

Results:

Tongkat Ali was associated with significant increases in total and free testosterone concentrations and muscular force. Males experienced a 61% increase in free testosterone and a 15.1% increase in total testosterone. Females experienced a 122% increase in free testosterone and a 48.6% increase in total testosterone.

Link:

https://doi.org/10.1002/ptr.5017

Study 11

Study type: 

Animal study (male rats)

Dose:

4 fractions of Tongkat Ali at a dosage of 25 mg/kg body weight

Results:

Tongkat ali (F2) and eurycomanone significantly increased the testosterone level from the Leydig cells. The plasma luteinizing hormone and follicle stimulating hormone were also higher than the control group.

Link:

https://doi.org/10.1016/j.jep.2012.11.013

Study 12

Study type: 

Cellular study (testicular interstitial cells)

Dose:

100μL solution of Eurycomanone at 0.1, 1.0 and 10μM

Results:

Eurycomanone significantly increased testosterone production dose-dependently at 0.1, 1.0 and 10.0 μM.

Link:

https://doi.org/10.1016/j.jep.2013.06.023

Study 1

Study type: 

Placebo-controlled clinical trial

Dose:

100mg per day

Additional interventions:

Intense strength training on alternate days

Participants:

14 healthy men

Duration:

5 weeks

Results:

Tongkat Ali supplementation was associated with:

• 4.1% Increase in lean body mass (from 52.26kg to 54.39kg) 

• 2.86% reduction in body fat (from 31.3% to 28.44%)

• 6.8% increase in strength

• 1.8cm increase in mean arm circumference (from 30.87cm to 32.67cm)

Link:

https://www.researchgate.net/publication/341998425_The_Ergogenic_Effect_of_Eurycoma_longifolia_Jack_A_Pilot_Study 

Study 2

Study type: 

Randomised placebo-controlled trial

Dose:

250mg of Tongkat Ali per day

Additional interventions:

High-intensity resistance training; 2500mg of branched-chain amino acids; 1020mg of beta-alanine. 

Participants:

32 young males with at least 1 year of experience in squatting, bench pressing and deadlifting.

Duration:

4 weeks

Results:

Tongkat Ali supplementation was associated with large strength increases in bench pressing (102kg to 108kg), squatting (120kg to 133kg) and deadlifting (158kg to 172kg), corresponding to an overall strength increase of 33kg. The placebo group experienced a much lower overall strength increase (24kg).

Year: 

2015

Link:

https://www.doi.org/10.1519/JSC.0000000000000995     

Study 3

Study type: 

Randomised, double-blind, placebo-controlled trial

Dose:

300mg

Participants:

40 men aged 30 to 35

Duration:

12 weeks

Results:

Tongkat Ali supplementation was associated with a strength increase of around 14kg in the back and leg muscles compared to the placebo group.

Year: 

2013

Link:

https://doi.org/10.4172/2161-0673.1000127 

Study 4

Study type: 

Clinical trial (uncontrolled)

Dose:

200mg per day

Participants:

13 physically active males and 12 physically active females aged 57 to 72

Duration:

5 weeks

Results:

Tongkat Ali supplementation was associated with a strength increase of 16.6% in men and 13.7% in women after 5 weeks. These increases in muscle strength indirectly reflected an increase in muscle mass.
* Strength was measured with a hand dynamometer. 

Year:

2013

Link:

https://doi.org/10.1002/ptr.5017  

Study 1

Study type: 

Randomised, double-blind, placebo-controlled trial

Dose:

300mg of Tongkat Ali per day

Participants:

109 healthy men aged from 30 to 55

Duration:

12 weeks

Results:

Tongkat Ali was associated with significant improvements in erectile function, sexual libido and overall sexual satisfaction scores. Tongkat Ali was also associated with higher sperm motility and semen volume. The study also indicated that healthy, younger males may require doses higher than 300mg per day to increase testosterone levels. 

Year: 

2012

Link:

https://doi.org/10.1155/2012/429268  

Study 2

Study type: 

Randomised, double-blind, placebo-controlled trial

Dose:

200mg per day

Participants:

26 men aged from 45 to 60 with mild erectile dysfunction 

Duration:

12 weeks

Results:

Tongkat Ali supplementation was associated with significant improvements in the frequency of sexual performance, sexual satisfaction, penile erection and hardness, and overall sexual wellbeing. Participants also experienced an average increase in total testosterone by 36%. No adverse effects were observed; liver and kidney values showed no significant changes from baseline.

Year: 

2014

Link:

https://doi.org/10.1155/2014/179529 

Study 3

Study type: 

Clinical trial (uncontrolled)

Dose:

200mg per day

Participants:

75 males (aged 33 on average) with idiopathic infertility

Duration:

3 months

Results:

Tongkat Ali supplementation was associated with significantly improved sperm quality (higher semen concentration, sperm motility and sperm concentration) and 11 spontaneous pregnancies. 

Link:

https://doi.org/10.1038/aja.2010.7  

Study 1

Study type: 

Randomised, double-blind, placebo-controlled trial

Dose:

50mg of Tongkat Ali per day

Additional interventions:

Multivitamin mix

Participants:

95 men and women aged from 25 to 65

Duration:

24 weeks

Results:

Tongkat Ali supplementation was associated with significant improvements in reported stress levels, quality-of-life, mood, vigour, emotional well-being and cognition.

Year:

2018

Link:

https://doi.org/10.29219/fnr.v62.1374  

Study 2

Study type: 

Randomised, double-blind, placebo-controlled trial

Dose:

200mg per day

Participants:

32 men and 31 women experiencing moderate stress

Duration:

4 weeks

Results:

Tongkat Ali supplementation was associated with significant improvements in tension (-11%), confusion (-15%) and anger (-21%). Tongkat Ali was also associated with a reduction in cortisol (−16%) and increased testosterone (+37%). Note that cortisol levels generally increase in response to stress.

Year: 

2022

Link:

https://doi.org/10.1186/1550-2783-10-28 

Products Containing Tongkat Ali

TURKESTERONE SCIENTIFIC STUDIES

Several studies have investigated the effects of turkesterone. We have summarised the most interesting results.

Study 1: Turkesterone outperforms anabolic steroids

Study type: 

Rodent study (male rats)

Purpose

To compare the anabolic activity of phytoecdysteroids and steranabols (anabolic steroids). Specifically, turkesterone and ecdysterone were compared with methyandrostenediol (Anabol) and nerobol (Dianabol). The effect of phytoecdysteroids upon protein-anabolic processes were judged by changes in body weight and the weight of internal organs and skeletal muscles. 

Dose:

5 mg/kg/day of phytoecdysteroids for 10 days or 10 mg/kg/day of Dianabol/Anabol for 10 days.

Results:

The results showed that the anabolic activity of turkesterone outperformed anabolic steroids. 

As visible in the table pictured, puberal and intact impuberal rodents experienced greater weight gain from turkesterone than from nerabol (Dianabol) and methylandrostenediol (Anabol).

These results are remarkable for several reasons:

1. Dianabol and Anabol are potent anabolic steroids that bodybuilders have used for decades.

2. Anabol and Dianabol generally lead to artificial weight gain due to water retention, unlike turkesterone and ecdysterone. 

3. Turkesterone and ecdysterone stimulated protein synthesis without adverse effects on the endocrine system.

Link:

https://doi.org/10.1007/BF02524596

Study 2

Study type: 

Non-randomised placebo-controlled clinical trial

Purpose:

To measure the effects of ecdysteroids (ecdysterone) on sports performance and body composition.

Interventions:

Ecdysterone supplement and 3 sessions of resistance training per week

Participants:

46 young men with at least 1 year of experience in weight-lifting (bench press, deadlift and squat)

Duration:

10 weeks

Results:

Compared to the placebo group, ecdysterone was correlated with significantly larger increases in muscle mass. The placebo group actually lost muscle mass.

Ecdysterone supplementation was also correlated with a significant increase in bench press and squat performance compared to the placebo group.

Importantly, biomarkers for liver or kidney toxicity did not increase after ecdysterone supplementation.

Year:

2019

Study sponsor:

WADA

Link:

https://doi.org/10.1007/s00204-019-02490-x   

Study 3

Study type: 

Animal & cellular study

Purpose

To elucidate the anabolic potency of ecdysterone (an ecdysteroid similar to turkesterone) in comparison to other known anabolic agents and to support the hypothesis of ERβ mediated action by in-silico modelling.

Dose:

5 mg/kg/day of phytoecdysteroids for 10 days or 10 mg/kg/day of methylandrostenediol (Anabol) or nerobol (Dianabol) for 10 days.

Results:

In the rodent study, ecdysterone exhibited a strong hypertrophic effect on the fibre size of the soleus muscle that was found to be even stronger than dianabol (metandienone), trenbolox (estradienedione), and SARMS1, all administered with the same dose (5 mg/kg for 21 days). 

In the cellular study, ecdysterone (1 µM) induced a significant increase of the diameter of myotubes (a cell found in muscle fibres) comparable to dihydrotestosterone (1 µM) and IGF1 (Insulin-Like Growth Factor, 1.3 nM). 

Conclusion:

The anabolic potency of ecdysterone was comparable or even higher than the anabolic androgenic steroids, SARMs or IGF-1. 

Year

2015

Link:

https://doi.org/10.5604/20831862.1144420 

Study 4

Study type: 

Cellular study

Purpose

To study the mechanism of action of phytoecdysteroids in mammalian tissue.

Results:

In human primary myotubes (cells found in muscle fibres), phytoecdysteroids increased protein synthesis by up to 20%.

Year

2008

Link:

https://doi.org/10.1021/jf073059z 

Study 5

Study type: 

Cellular study

Purpose

To evaluate whether phytoecdysteroids increase protein synthesis.

Results:

20-hydroxyecdysone (ecdysterone), a common phytoecdysteroid in both insects and plants, increased protein synthesis in myotubes (cells found in muscle fibres) by up to 16%.

Year

2010

Link:

https://doi.org/10.1016/j.steroids.2010.03.008 

Products Containing Turkesterone

CISTANCHE SCIENTIFIC STUDIES

We have summarised the most interesting studies of Cistanche related to depression, cognitive health, testosterone levels, sperm quality, erectile function and hair loss.

Study 1

Study type: 

Animal study (rats)

Purpose:

To determine the effects of Cistanche tubulosa extract on hormone levels and testicular steroidogenic enzymes in rats.

Results:

Cistanche tubulosa increased blood levels of testosterone and progesterone. It also increased sperm count 2.3 to 2.7-fold, increased sperm motility 1.3 to 1.4-fold, decreased abnormal sperm 0.76 to 0.6-fold, and increased the expression (activation) of the steroidogenic enzymes CYP11A1, CYP17A1, and CYP3A4. Steroidogenic enzymes are enzymes that are involved in steroid biosynthesis.

Conclusion:

Cistanche tubulosa extract decreased abnormal sperm and increased testosterone, progesterone, sperm count, sperm motility and the activation of enyzmes that are involved in the synthesis of steroid hormones. 

Year

2016

Link:

https://doi.org/10.3109/13880209.2015.1050114 

Study 2

Study type: 

Cellular and animal study (diabetic rats)

Purpose:

To investigate the anti-inflammatory and protective effects of echinacoside in Cistanche tubulosa extracts on the reproductive system of male diabetic rats (echinacoside is an active component of Cistanche tubulosa).

Results:

Rats treated with various concentrations of echinacoside in Cistanche tubulosa extracts exhibited higher levels of testosterone than the non-treated diabetic rats. Similarly, the results of the cellular study indicated that eichinacoside restored the testosterone synthesis pathway. 

Echinacoside also improved blood sugar levels, insulin resistance (the responsiveness of cells to insulin), leptin resistance (the body’s responsiveness to leptin, a hormone that signals the brain to stop eating when enough body fat has been stored), and lipid peroxidation (a process that causes oxidative deterioration of lipids, the fundamental building block of cells).

Summary:

Cistanche tubulosa and echinacosides increased testosterone and displayed anti-inflammatory and antioxidant benefits.

Year

2018

Link:

https://doi.org/10.3390/nu10101562

Study 3

Study type: 

Animal study (rats)

Purpose:

To investigate the proactive effects of Cistanche tubulosa and echinacoside (an active ingredient of Cistanche) against testicular and sperm toxicity.

Results:

Cistanche tubulosa and echinacoside normalised blood testosterone and reversed abnormalities in sperm characteristics and testicular structure. Cistanche and echinacoside also increased steroidogenic enzymes (enzymes involved in the production of steroid hormones), indicating that testosterone production was improved.

The results are especially interesting as the testicular toxicity was induced in the rats via a toxic chemical called bisphenol A (BPA) which has been used to make many plastics such as food containers since the 1950s. BPA is known to be an endocrine-disruptor, meaning that it interferes with the body’s hormones. Studies have indicated that BPA has estrogen-like activity and exhibits inhibitory effects on testosterone synthesis and developmental toxicity in the reproductive organs. Daily BPA exposure is unavoidable for most people. 

This study indicated that Cistanche may help to protect against the potential effects of daily BPA exposure.

Conclusion:

Cistanche tubulosa and echinacoside improved testicular and sperm damage in rats.

Year

2016

Link:

https://doi.org/10.1016/j.jep.2016.07.033 

Study 4

Study type: 

Animal study (rats)

Purpose:

To investigate the protective effects of echinacoside (echinacoside is an active component of Cistanche tubulosa) against infertility in rats.

Results:

Echinacoside increased sperm quantity and protected against oligoasthenospermia (low sperm count and sperm motility, a primary cause of male infertility). Echinacoside blocked androgen-receptor activity (the binding sites of testosterone) in the hypothalamus, thereby increasing testosterone. 

Conclusion:

Echinacoside increased sperm quantity and protected against low sperm count and low sperm motility. It also increased levels of testosterone and luteinizing hormone.

Year

2018

Link:

https://doi.org/10.1038/s41598-018-22211-1 

Study 5 (Growth hormone)

Study type: 

Animal study (rats)

Results:

Eichanoside from Cistanche tubulosa stimulated growth hormone secretion via activation of the ghrelin receptor. Note that the ghrelin receptor is the target of performance enhancing drugs and SARMS (drugs similar to anabolic steroids).

Conclusion:

Eichanoside from Cistanche tubulosa stimulated the secretion of growth hormone.

Year

2016

Link:

https://doi.org/10.1038/s41598-018-22211-1 

Study 1

Study type: 

Animal study (rats)

Purpose:

To examine the effects of Cistanche deserticola extract on penis erectile response.

Results:

The findings indicated that Cistanche deserticola ​​shortened erectile latency and prolonged erectile duration to minimise the negative effects of castration. 

The results also indicate that Cistanche deserticola regulated the blood concentration of luteinizing hormone to normal levels. In men, luteinizing hormone stimulates Leydig cells in the testes to produce testosterone. This acts to support sperm production.

Conclusion:

In castrated rats, the results indicated that Cistanche deserticola decreased the time taken to get an erection and increased the duration of erections.

Year

2016

Link:

https://pubmed.ncbi.nlm.nih.gov/27087079/ 

Study 1

Study type: 

Randomised, double-blinded, placebo-controlled clinical trial

Purpose: 

To investigate the efficacy of Cistanche tubulosa and Laminaria japonica in preventing hair loss and promoting scalp health.

Number of participants:

94

Duration:

16 weeks

Results:

Researchers observed a statistically significant increase in the hair density of the test group after 16 weeks of Cistanche tubulosa and Laminaria japonica. Researchers also observed a statistically significant increase in hair diameter in the test group compared to control group at week 16. The test group also experienced greater improvements in dandruff compared to the control.

Conclusion:

Cistanche tubulosa extract was associated with improvements in patterned hair loss, dandruff and inflammation of the scalp.

Year

2015

Link:

https://doi.org/10.7762/cnr.2015.4.2.124 

Study 1 (Depression)

Study type: 

Animal study (mice)

Purpose:

To examine the antidepressant effects of Cistanche tubulosa.

Results:

The results showed promising effects as a potential therapy for depression.

The mice treated with Cistanche displayed: 

1. An improved ability of spatial learning and memory.

2. Downregulated monoamine oxidase activity. It is important to note that monoamine oxidase inhibitors are used as antidepressant drugs. Monoamine oxidase is an enzyme that serves to inactivate monoamine neurotransmitters such as dopamine and serotonin.

3. Upregulated dopamine concentration in the brain (dopamine is a chemical involved in feelings of pleasure and motivation).

4. Downregulated blood concentration of corticosterone, indicating that the mice had reduced stress levels (corticosterone is a biomarker of stress levels).

Conclusion:

Cistanche improved markers of depression.

Year

2017

Link:

https://doi.org/10.1155/2017/3925903

Study 2 (Depression)

Study type: 

Animal study (rats)

Purpose:

To examine the impact of Cistanche tubulosa on markers of depression.

Results:

Cistanche tubulosa extract significantly improved depression-like behaviours in rats under chronic unpredictable stress. Cistanche restored  levels of serotonin (serotonin plays a key role in mood stabilisation and sleep). Cistanche also restored BDNF protein expression (loss of BDNF is thought to be involved in depression). 

Year

2018

Link:

https://doi.org/10.3389/fphar.2018.00967 

Study 3 (Depression)

Study type: 

Animal study (rats)

Purpose:

To explore the active components of Cistanche tubulosa against depression

Results:

Molecules called glycosides from the stems of Cistanche tubulosa improved depression-like behaviours in rats.

Year

2021

Link:

https://doi.org/10.1016/j.phymed.2021.153471

Study 4 (Alzheimer's disease)

Study type: 

Animal study (Alzheimer’s disease-like rat model)

Propose:

To evaluate the effect of Cistanche in rats with Alzheimer’s disease-like pathology

Results:

More specifically, Cistanche reversed cholinergic and dopaminergic dysfunction in rats. The results are promising as Alzheimer’s disease is associated with cholinergic and dopaminergic dysfunction.

Conclusion:

Cistanche reversed dysfunction associated with Alzheimer’s disease.

Year

2014

Link:

https://doi.org/10.1186/1472-6882-14-202 

Study 5 (Parkinson's disease)

Study type: 

Animal study (rodent model of Parkinson’s disease)

Purpose:

To identify potential therapeutic effects of Cistanche on Parkinson’s disease.

Results:

Cistanche had protective effects on dopaminergic neurons in a rodent model of Parkinson’s disease. This is promising as Parkinson’s disease mainly affects the dopamine-producing (“dopaminergic”) neurons.

Conclusion:

Cistanche treatment resulted in protective effects against Parkinson’s disease.

Year

2016

Link:

https://doi.org/10.3389/fnagi.2016.00295 

Products Containing Cistanche

Fadogia Agrestis Scientific Studies

We have summarised the most interesting studies on Fadogia agrestis.

Study 1 (Testosterone & Libido)

Study type: 

Animal study (rats)

Study length:

5 days

Results:

The various doses of Fadogia agrestis (18 mg/kg, 50 mg/kg and 100 mg/kg) produced two-, three- and six-fold increases in blood testosterone compared with the control.

All doses of Fadogia agrestis significantly prolonged the ejaculatory latency and improved markers of libido. It increased mount and intromission frequency (higher intercourse frequency) and reduced mount and intromission latency (reduced time before intercourse).

Conclusion:

All doses of Fadogia agrestis increased testosterone levels, delayed ejaculation, increased intercourse frequency and improved markers of libido. 100 mg/kg of Fadogia agrestis increased blood testosterone levels by 600%. 

Year

2005

Link:

https://doi.org/10.1111/j.1745-7262.2005.00052.x 

Study 2 (Erectile Dysfunction)

Study type: 

Animal study (rats)

Results:

Fadogia agrestis restored the NO/cGMP pathway (a mediator of erections) and key enzymes in the penile and testicular tissues of male rats. 

Conclusion:

Fadogia agrestis may help improve erectile dysfunction, although clinical trials are needed.

Year

2023

Link:

https://doi.org/10.1007/s43032-022-01050-6 

Products Containing Fadogia

ECDYSTERONE SCIENTIFIC STUDIES

Several studies have investigated the effects of ecdysterone. We have summarised the most interesting results.

Study 1

Study type: 

Non-randomised placebo-controlled clinical trial

Purpose:

To measure the effects of ecdysteroids (ecdysterone) on sports performance and body composition.

Interventions:

Ecdysterone supplement and 3 sessions of resistance training per week

Participants:

46 young men with at least 1 year of experience in weight-lifting (bench press, deadlift and squat)

Duration:

10 weeks

Results:

Compared to the placebo group, ecdysterone was correlated with significantly larger increases in muscle mass. The placebo group actually lost muscle mass.

Ecdysterone supplementation was also correlated with a significant increase in bench press and squat performance compared to the placebo group.

Importantly, biomarkers for liver or kidney toxicity did not increase after ecdysterone supplementation.

Year:

2019

Study sponsor:

WADA

Link:

https://doi.org/10.1007/s00204-019-02490-x   

Study 2

Study type: 

Animal & cellular study

Purpose

To elucidate the anabolic potency of ecdysterone in comparison to other known anabolic agents and to support the hypothesis of ERβ mediated action by in-silico modelling.

Dose:

5 mg/kg/day of phytoecdysteroids for 10 days or 10 mg/kg/day of methylandrostenediol (Anabol) or nerobol (Dianabol) for 10 days.

Results:

In the rodent study, ecdysterone exhibited a strong hypertrophic effect on the fibre size of the soleus muscle that was found even stronger compared to dianabol (metandienone), trenbolox (estradienedione), and SARMS1, all administered in the same dose (5 mg/kg body weight, for 21 days). 

In the cellular study, ecdysterone (1 µM) induced a significant increase of the diameter of myotubes (a cell found in muscle fibres) comparable to dihydrotestosterone (1 µM) and IGF1 (Insulin-Like Growth Factor, 1.3 nM). 

Conclusion:

The anabolic potency of the ecdysterone was comparable or even higher than the anabolic androgenic steroids, SARMs or IGF-1. 

Year

2015

Link:

https://doi.org/10.5604/20831862.1144420 

Study 3

Study type: 

Animal study (male rats)

Purpose

To compare the anabolic activity of phytoecdysteroids and steranabols (anabolic steroids). Specifically, ecdysterone and turkesterone were compared with methyandrostenediol (Anabol) and nerobol (Dianabol). The effect of phytoecdysteroids upon protein-anabolic processes were judged by changes in body weight and the weight of internal organs and skeletal muscles. 

Dose:

5 mg/kg/day of phytoecdysteroids for 10 days or 10 mg/kg/day of methylandrostenediol (Anabol) or nerobol (Dianabol) for 10 days.

Results:

The results showed that the anabolic activity of phytoecdysteroids outperformed anabolic steroids. 

As visible in the table below, puberal rodents experienced similar weight gain from ecdysterone similar to the anabolic steroid Anabol (methylandrostenediol). Intact impuberal rodents experienced greater weight gain from ecdysterone than from Anabol.

These results are significant for several reasons:

- Anabol leads to artificial weight gain due to water retention, unlike ecdysterone. 

- The phytoecdysteroids (ecdysterone and turkesterone) stimulated protein synthesis without adverse effects on the endocrine system.

Year

2000

Link:

https://doi.org/10.1007/BF02524596 

Study 4

Study type: 

Cellular study

Purpose

To study the mechanism of action of phytoecdysteroids in mammalian tissue.

Results:

In human primary myotubes (cells found in muscle fibres), phytoecdysteroids increased protein synthesis by up to 20%.

Year

2008

Link:

https://doi.org/10.1021/jf073059z 

Study 5

Study type: 

Cellular study

Purpose

To evaluate whether phytoecdysteroids increase protein synthesis.

Results:

20-hydroxyecdysone (ecdysterone), a common phytoecdysteroid in both insects and plants, increased protein synthesis in myotubes (cells found in muscle fibres) by up to 16%.

Year

2010

Link:

https://doi.org/10.1016/j.steroids.2010.03.008 

Products Containing Ecdysterone

Horny Goat Weed Scientific Studies

We have summarised some of the most interesting scientific studies on horny goat weed and icariin. Icariin is the main active component of horny goat weed.

Study 1

Study type: 

Rats with erectile dysfunction due to nerve injury

Purpose

To evaluate the effects of icariin (icariin is believed to be the main active component of horny goat weed) on penile blood flow and tissues in cavernous nerve-injured rats (the cavernous nerve is the main autonomic nerve regulating penile erection). 

Dose:

1, 5, and 10 mg/kg of icariin 

Duration:

4 weeks

Results:

Daily treatment with low-dose icariin for 4 weeks improved penile blood flow dynamics in rats with a cavernous nerve injury (the nerve that regulates erections). 

Compared to the control, the researchers detected significantly higher nNOS in the penile tissue. Note that nNOS, or neuronal NO synthase, generates nitric oxide which initiates penile erections. 

Conclusion:

This study indicates that icariin (found in horny goat weed) may improve penile blood flow. Note that penile blood flow is essential for erections. Clinical studies are needed to investigate its efficacy in humans.

Year

2010

Link:

https://doi.org/10.1111/j.1743-6109.2009.01699.x 

Study 2

Study type: 

Rats with erectile dysfunction due to nerve injury

Purpose

To investigate the effect of icariin on erectile function and the expression of nitric oxide synthase* in castrated rats.
*Nitric oxide synthase generates nitric oxide that initiates penile erections.

Dose:

1 mg/kg/day and 5 mg/kg/day

Duration:

4 weeks

Results:

Several markers of erectile function improved in most treatment groups: 

1. In 2 out of 3 treatment groups, the expression (activation) of two forms of nitric oxide synthase significantly improved in the erectile tissue of rats. Note that nitric oxide synthase generates nitric oxide which initiates penile erections.

2. In 1 of the treatment groups, phosphodiasterase-5 was significantly decreased. Note that phosphodiesterase-5 interferes with blood flow to the penis that is needed for an erection.

Conclusion:

Oral treatment with icariin for 4 weeks potentially improves erectile function in rodents.

Year

2005

Link:

https://doi.org/10.1111/j.1745-7262.2005.00066.x 

Study 3

Study type: 

Rats with erectile dysfunction

Purpose

To investigate the effects of orally administered icariin on the expression (levels) of nitrogen oxide synthase* in the erectile tissue of rats with erectile dysfunction.

Dose:

5 mg/kg/day or 10 mg/kg/day

Duration:

30 days

Results:

Chronic oral treatment with icariin increases erectile function and restores nitric oxide synthase* in the erectile tissue of rats.

Year

2004

Link:

https://pubmed.ncbi.nlm.nih.gov/15329286/ 

*(note that nitric oxide synthase generates nitric oxide which initiates penile erections)

Study 4

Study type: 

Laboratory study

Purpose

To investigate the effect of icariin on phosphodiesterase-5

Results:

Icariin exhibited inhibitory effects on all forms of phosphodiesterase-5. 

Year

2006

Link:

https://doi.org/10.1016/j.urology.2006.09.031 

Study 1 (estrogen, cholesterol and triglyceride levels in postmenopausal women)

Study type: 

Randomised, double-blind, placebo-controlled clinical trial

Purpose: 

To evaluate the effects of dried Epimedium extract on blood lipid levels and sex hormone levels (estradiol, progesterone and testosterone).

Background information:

Horny goat weed contains phytoestrogens, compounds that act like the hormone estrogen. 

Dose:

300mL of hot water Epimedium extract (with 25% icariin)

Participants:

90 postmenopausal women

Duration:

6 months

Results:

Epimedium water extract was associated with a significant increase in blood levels of estradiol (an estrogen hormone) compared with the pre-treatment level. It was also associated with a significant decrease in total cholesterol and total triglyceride levels. 

Year

2008

Link:

https://doi.org/10.1002/ptr.2451 

Study 2 (Bone Health)

Study type: 

Randomised, double-blind, placebo-controlled clinical trial

Purpose: 

To investigate the effect of the phytoestrogen flavonoids derived from Epimedium brevicornum maxim (horny goat weed) on bone loss in postmenopausal women.

Dose:

60mg icariin (with 15mg Daidzein and 3mg Genistein) paired with 300mg elemental calcium daily

Participants:

85 healthy late postmenopausal women

Duration:

24 months

Results:

Phytoestrogen flavonoids from horny goat weed were associated with preventative effects on bone loss in late postmenopausal women.

Year

2007

Link:

https://doi.org/10.1359/jbmr.070405 

Products Containing Horny Goat Weed

BEETROOT SCIENTIFIC STUDIES

Dozens of clinical trials have investigated the effects of beetroot supplementation. We have summarised some the most interesting scientific studies.

Study 1

Study type: 

Randomised, double-blind, placebo-controlled trial

Dose:

250 mL/day of beetroot juice (containing ~6.4mmol of nitrate) or a placebo (250 mL of nitrate-depleted beetroot juice)

Participants:

64 hypertensive men and women aged 18 to 85 

Duration:

4 weeks 

Results:

Daily supplementation with beetroot juice (dietary nitrate) was associated with a reduction in blood pressure. Specifically, the mean 24h ambulatory blood pressure decreased by 7.7/5.2 mmHg and the mean clinical blood pressure decreased by 7.7/2.4 mmHg. These reductions are clinically significant as they resemble the average reduction in blood pressure after a single anti-hypertensive drug at standard dose (9.1/5.5 mmHg). The authors of the study suggested that dietary nitrate could be used as an adjunctive therapy for managing hypertension.

Year:

2014

Link:

https://doi.org/10.1161/HYPERTENSIONAHA.114.04675 

Study 2

Study type: 

Randomised, double-blind, placebo-controlled feasibility trial 

Dose

Participants were randomly assigned to consume either:

1. High-nitrate beetroot juice (∼400 mg nitrate) and folic acid (∼5 mg folic acid) (N+F)

2. High-nitrate beetroot juice and placebo (N+P)

3. Nitrate-depleted beetroot juice and placebo (P+P)

Participants:

47 men and women aged 50 to 70 with BMIs between 26 and 29

Duration:

60 days

Results:

Supplementation with beetroot juice (dietary inorganic nitrate) was associated with lower systolic and diastolic blood pressure. At the end of the study, 24h systolic blood pressure dropped by −10.8, −6.1 and −0.3 mmHg in the N+P, N+F, and P+P groups, respectively. There was a significant decrease in 24h diastolic blood pressure in the N+P group (−5.4 mmHg), whereas changes were not significant in the N+F (−1.8 mmHg) and P+P (1.6 mmHg) groups.

Year:

2020

Link:

https://doi.org/10.1093/jn/nxaa170  

Study 3

Study type: 

Randomised, double-blind, placebo-controlled trial

Dose:

314 mM of nitrate tablets or a placebo (nitrate-free tablets). The nitrate tablets consisted of nitrate-rich beetroot extract 20mg, thiamine mononitrate 90mg, potassium nitrate 480mg, ascorbic acid 150mg, folic acid 200mcg, methylcobalamin 200mcg, calcium 115mg, pomegranate fruit extract 5mg and green coffee bean extract 115mg. Ascorbic acid was added to facilitate NO bioavailability.

Participants:

67 hypertensive men and women with a mean age of 59

Duration:

12 weeks

Results:

Nitrate tablets were associated with a larger average reduction in systolic blood pressure than the placebo (-12.5 vs -6.19 mmHg at the end of the study). Nitrate tablets were associated with a reduction in diastolic blood pressure (-4.7 mmHg on average), whilst no significant reduction was observed in the placebo group. Endothelial function also improved by 0.8 after 12 weeks (compared to a 0.1 improvement in the placebo group). The authors concluded that endothelial function improved robustly, reducing both systolic and diastolic blood pressure in hypertensive individuals.

Year:

2020

Link:

https://doi.org/10.1016/j.clnesp.2020.08.007 

Study 4

Study type: 

Randomised, single-blind, cross-over postprandial trial (pilot study)

Dose:

In study 1, participants were randomly assigned to consume either 0, 100, 250 or 500mL of beetroot juice (each having a nitrate concentration of <0.5, 2.3, 5.7 and 11.4 mmol respectively). In study 2, participants were randomly assigned to consume either 200g of unfortified bread (<0.5 mmol of nitrate) or 200g of bread fortified with white or red beetroot (1.6 and 1.8 mmol of nitrate respectively). All participants consumed a low-nitrate/nitrite diet for 1 day before each study.

Participants:

18 healthy normotensive males in study 1 and 14 healthy normotensive males in study 2.  

Duration:

Acute: blood pressure was measured over a 24h period following the consumption of beetroot juice, beetroot-fortified bread and the controls.

Results:

Supplementation with beetroot juice or beetroot-fortified bread was associated with larger reductions in blood pressure than the control. The peak reduction in blood pressure occurred after 2-3 hours:

- 100mL of beetroot juice was associated with a 13.1/16.6 mmHg reduction in blood pressure. 

- 250mL of beetroot juice was associated with a 20.5/14.6 mmHg reduction in blood pressure.

- 500mL of beetroot juice was associated with a 22.2/18.3 mmHg reduction in blood pressure.

- Bread fortified with white beetroot was associated with a 19.3/16.5 mmHg reduction in blood pressure.

  • Bread fortified with red beetroot was associated with a 23.6/23.2 mmHg reduction in blood pressure.

These results suggest that nitrate in beetroot may significantly help to reduce blood pressure. The reductions in blood pressure after the consumption of fortified bread suggest that processed beetroot may lower blood pressure to a similar degree as unprocessed beetroot. Thus, beetroot supplements may help to reduce overall blood pressure.

Year:

2015

Link:

https://doi.org/10.1038/jhh.2014.114  

Study 5

Study type: 

Randomised non-blinded postprandial trial

Dose:

The experimental group consumed 500mL of beetroot juice with a mean nitrate concentration of 45.0±2.6 mMol/L (2.79g/L). The control group consumed water.

Participants:

14 healthy subjects  

Duration:

Acute: blood pressure was measured over a 24h period following the consumption of beetroot juice. 

Results:

Beetroot juice supplementation (dietary nitrate) was associated with larger reductions in blood pressure than the control. Specifically, blood pressure dropped by 10.4/8 mmHg after 2.5 hours compared to the control. The drop in blood pressure was correlated with increases in plasma nitrite concentration. This suggests that dietary nitrate may underlie the beneficial effects of beetroot. After 24 hours, systolic blood pressure was 4.4 mmHg lower with beetroot juice than water.

Year:

2008

Link:

https://doi.org/10.1161/HYPERTENSIONAHA.107.103523 

Study 6

Study type: 

Randomised non-blinded crossover trial

Dose

250mL of beetroot juice (containing 5.5 mmol of nitrate) or placebo (250mL of water)

Participants:

9 healthy men and women.

Duration:

Acute (less than 24 hours)

Results:

Supplementation with beetroot juice (dietary nitrate) was associated with a 5.4 mmHg reduction in systolic blood pressure. The authors suggested that a dietary nitrate approach to cardiovascular disease may have therapeutic use.

Year:

2010

Link:

https://doi.org/10.1161/HYPERTENSIONAHA.110.153536  

Study 7

Study type: 

Randomised, double-blind, crossover trial

Dose

2 x 70 mL/day of organic beetroot juice (each containing 4.8 mmol of nitrate). The placebo consumed nitrate-depleted beetroot juice.

Participants:

12 healthy, normotensive, non-smoking, older adults (6 males and 6 female)

Duration:

2.5 days

Results:

2.5 days of dietary nitrate supplementation was associated with a four-fold increase in plasma nitrite concentration and significant reductions in resting blood pressure. More specifically, plasma nitrite increased to 418% of the placebo value, and blood pressure decreased by 5/3 mmHg relative to the placebo (115/70 vs 120/73 mmHg). The authors suggested that nitrate supplementation could potentially reduce the risk of hypertension and cardiovascular disease in older adults.

Year:

2013

Link:

https://doi.org/10.1152/ajpregu.00406.2012  

Study 8

Study type: 

Randomised, double-blind, placebo-controlled crossover trial

Dose:

Nitrate-rich beetroot juice (12.9 mmol of nitrate) or a placebo (nitrate-depleted beetroot juice (0.5 mmol of nitrate)

Participants:

20 men and women (mean age: 62.5) with uncontrolled hypertension 

Duration:

7 days

Results:

Supplementation with beetroot juice (dietary nitrate) was associated with a significant reduction in systolic and diastolic blood pressure compared to the placebo. Beetroot juice supplementation was also significantly associated with increased plasma nitrite. Significant decreases in 24h (−8/−4 mmHg) and day blood pressure (−9/−4 mmHg) profiles were observed.

Year:

2018

Link:

https://doi.org/10.1017/S0007114518000144   

Study 9

Study type: 

Randomised, double-blind, placebo-controlled crossover trial

Dose:

150 mL of nitrate-rich beetroot juice (10.5 mmol of nitrate) or a placebo (1 mmol nitrate) 2.25 hours prior to a 30-min treadmill walk

Participants:

13 younger (18–30) and 11 older (50–70) normotensive adults

Duration:

Acute (3.5 hours)

Results:

Supplementation with beetroot juice (dietary nitrate) was associated with a significant reduction in systolic blood pressure in both age groups and diastolic blood pressure in older adults. Beetroot juice was also associated with increased plasma nitrate and nitrite concentrations.

The authors concluded that acute supplementation with beetroot may reduce blood pressure.

Year:

2019

Link:

https://doi.org/10.3390/nu11071683 

Study 10

Study type: 

Randomised, placebo-controlled, single-blind crossover trial

Dose:

140 mL of beetroot juice (containing 7.58 millimoles of nitrate) or a placebo (163 ml of prune juice with less than 0.01 millimoles of nitrate)

Participants:

15 patients with chronic obstructive pulmonary disease (11 males and 3 females)

Duration:

48 hours

Results:

Supplementation with beetroot juice (dietary nitrate) was associated with a significant reduction in resting systolic blood pressure (-8 mmHg), end-of-exercise diastolic blood pressure (-5 mmHg) and a trend for a decrease in resting diastolic blood pressure (−3 mmHg). Beetroot juice was also associated with increased plasma nitrate (+938%) and nitrite (+379%) relative to the placebo.

The authors concluded that dietary nitrate supplementation may reduce blood pressure and elevate plasma nitrate and nitrite concentrations. 

Year:

2015

Link:

https://doi.org/10.1016/j.niox.2014.10.007 

Study 11

Study type: 

Randomised, double-blind, placebo-controlled crossover trial

Dose:

Nitrate-rich beetroot juice (500mg/8.1mmol of nitrate) or a placebo (nitrate-depleted beetroot juice with less than 0.08 mmol of nitrate) 

Participants:

18 untreated hypertensives aged 44 on average.

Duration:

Acute (8 hours)

Results:

Supplementation with beetroot juice (dietary nitrate) was associated with a larger reduction in ambulatory systolic and diastolic blood pressure (-6.7/-5.2 mmHg) compared to the placebo (-0.8/-1.7 mmHg) after 8 hours.

Year:

2018

Link:

https://doi.org/10.1111/micc.12525 

Study 12

Study type: 

Randomised controlled trial

Dose:

∼5.76 mmol of nitrate in the form of a concentrated beetroot juice drink (55 mL), a non-concentrated beetroot juice drink (456 mL) and a solid beetroot flapjack (60 g). A drink containing soluble beetroot crystals (∼1.40 mmol of nitrate) and a control drink (70mL of deionised water) were also ingested.

Participants:

10 healthy males

Duration:

Acute (24 hours)

Results:

Beetroot juice (dietary nitrate) was associated with lower blood pressure and higher concentrations of nitric oxide metabolites. All nitrate-rich vehicles in the study were associated with elevated plasma, salivary and urinary nitric oxide metabolites compared with baseline and the control.

Year:

2018

Link:

https://doi.org/10.1016/j.niox.2017.12.001 

Study 13

Study type: 

Randomised, double-blind, placebo-controlled crossover trial

Dose:

70mL of beetroot juice (400 mg of nitrate) or a placebo (nitrate-depleted beetroot juice)

Participants:

14 healthy males (aged 22 on average) 

Duration:

15 days

Results:

Compared with the placebo, beetroot juice (dietary nitrate) was associated with reductions in systolic and diastolic blood pressure, mean arterial pressure and total peripheral resistance at rest and during exercise.

Beetroot juice was also associated with significant increases in baseline concentrations of plasma nitrate and nitrite compared to the placebo.

Year:

2015

Link:

https://doi.org/10.1152/ajpregu.00099.2015 

Study 14

Study type: 

Randomised, double-blind, placebo-controlled trial

Dose:

500 mL/day of beetroot juice (containing ∼6.2 mmol of nitrate) or a placebo (500 mL/day of nitrate-depleted beetroot juice)

Participants:

9 normotensive, physically active males

Duration:

6 days

Results:

Short-term supplementation with beetroot juice (dietary nitrate) was associated with significant increases in plasma nitrite (+105%) and reductions in systolic blood pressure (-5 mmHg) in normotensive young men consuming a normal, balanced diet. The placebo had no effect on systolic, diastolic or mean arterial blood pressure.

Year:

2011

Link:

https://doi.org/10.1152/japplphysiol.01070.2010 

Study 15

Study type: 

Randomised double-blind crossover trial

Dose

24 mmol of potassium nitrate (1488mg of nitrate) in capsules or a placebo (24 mmol of potassium chloride)

Participants:

21 healthy men and women

Duration:

Acute (less than 24 hours)

Results:

Potassium nitrate supplementation was associated with substantial reductions in systolic and diastolic blood pressure over 24 hours, whereas a similar dose of potassium chloride did not alter blood pressure over the same time period. These findings suggest that the changes in blood pressure were not attributable to the potassium content. Instead, the changes were likely dependent on the endogenous conversion to nitrite and, thereupon, to nitric oxide: the changes in plasma nitrite correlated closely with reductions in blood pressure.

Kapil et al.’s findings also showed dose-dependent reductions in systolic blood pressure with incremental doses of inorganic nitrate (4mmol and 12mmol).

Year:

2010

Link:

https://doi.org/10.1161/HYPERTENSIONAHA.110.153536  

Study 16

Study type: 

Systematic review

Intervention under study:

Beetroot juice (dietary inorganic nitrate) supplementation

Studies reviewed:

11 randomised controlled trials published between 2008 and 2018 

Results:

The review concluded that supplementation with beetroot juice may reduce blood pressure in different populations, probably through the nitrate-nitrite/nitric oxide pathway and secondary metabolites found in beetroot. The review also concluded that beetroot juice may significantly decrease the risk of suffering cardiovascular events, and the authors believe that beetroot juice should be promoted as a key component of a healthy lifestyle to control blood pressure in healthy and hypertensive individuals.

Year:

2018

Link:

https://doi.org/10.3390/biom8040134 

Study 17

Study type: 

Systematic review and meta-analysis

Intervention under study:

Dietary nitrate supplementation

Outcome under study:

Medium-term effects of dietary nitrate supplementation on systolic and diastolic blood pressure.

Studies included:

13 randomised clinical trials with 7 to 65 participants per study. Most of the trials were placebo-controlled (75%). 

Results:

Overall, dietary nitrate supplementation for more than one week was associated with a significant decrease in systolic and diastolic blood pressure. The pooled effect for the two interventions showed a reduction in systolic blood pressure (-4.1 mmHg) and diastolic blood pressure (-2.0 mmHg). 

Year:

2017

Link:

https://doi.org/10.1097/HJH.0000000000001305 

Study 18

Study type: 

Systematic review and meta-analysis

Intervention under study:

Dietary nitrate supplementation. The intervention time ranged from 3 to 60 days with daily dosages of 70–250 mL of beetroot juice.

Outcome under study:

The role of dietary nitrate in lowering blood pressure in patients older than 18 with arterial hypertension ( > 130/80 mmHg).

Studies included:

7 single/double-blinded randomised controlled trials published between 2013 and 2020.

Results:

Inorganic nitrate derived from beetroot juice was associated with reductions in systolic blood pressure in patients with arterial hypertension. The authors concluded that dietary nitrate from beetroot juice may be an effective method to reduce the blood pressure of patients with arterial hypertension (in interventions up to 2 months duration).

Year:

2022

Link:

https://doi.org/10.3389/fnut.2022.823039 

Study 19

Study type: 

Systematic review and meta-analysis

Intervention under study:

Dietary inorganic nitrate/nitrite

Outcome under study:

Prevention and treatment of cardiovascular disease risk factors in humans

Studies included:

34 studies were included for qualitative synthesis, 23 of which were eligible for meta-analysis.

Results:

Inorganic nitrate intake was associated with significant reductions in resting blood pressure (systolic blood pressure: -4.80 mmHg; diastolic blood pressure: 1.74 mmHg).

Year:

2018

Link:

https://doi.org/10.1093/nutrit/nuy005 

Study 20

Study type: 

Randomised, double-blind, placebo-controlled trial 

Dose

Beetroot juice with 6.5–7.3 mmol of nitrate. The placebo group received nitrate-depleted beetroot juice(<0.06 mmol nitrate)

Participants:

15 healthy, normotensive men and women aged 22 to 40

Duration:

Acute: 24 hours on two occasions (crossover)

Results:

Supplementation with beetroot juice containing inorganic nitrate was associated with lower aortic systolic blood pressure after 30 minutes (-5.2 mmHg).

Year:

2019

Link:

https://doi.org/10.3389/fphys.2019.00047  

Study 21

Study type: 

Randomised, double-blind, placebo-controlled crossover trial

Dose:

70mL of beetroot juice (6.1 mmol nitrate). The placebo group consumed 70mL of nitrate-depleted beetroot juice.

Participants:

20 patients suffering from heart failure with preserved ejection fraction (aged 69 on average) 

Duration:

First phase: acute (24 hours)

Second phase: 1 week 

Results:

In both study phases, supplementation with nitrate-rich beetroot juice was associated with significant reductions in systolic blood pressure (resting) and increases in plasma nitrate and nitrite. After a single, acute dose of nitrate-rich beetroot juice, resting systolic blood pressure was significantly lower than the placebo (127 mmHg vs. 134 mmHg).

Compared to the placebo, plasma nitrite levels increased significantly after the nitrate-rich beetroot juice (38% after an acute dose and 129% after 1 week of daily doses).

The authors concluded that beetroot may significantly improve blood pressure in elderly patients with heart failure.

Year:

2016

Link:

https://doi.org/10.1016/j.jchf.2015.12.013   

Study 22

Study type: 

Randomised placebo-controlled crossover trial

Dose

500 mL/day of beetroot juice (5.2 mmol of nitrate/day) and placebo (500 mL/day of juice). Participants also engaged in moderate-intensity exercise after 2.5 hours and on day 5 and day 15. 

Participants:

8 healthy subjects (5 males and 3 females) with an average age of 29

Duration:

Acute (2.5 hours) and chronic (up to 15 days)

Results:

Nitrate-rich beetroot juice supplementation was associated with significantly lower systolic and diastolic blood pressure throughout the supplementation period (∼-4%). It was also associated with significantly elevated plasma nitrite concentration (+39% after 2.5 hours; +25% after 5 days; and +46% after 15 days).

The results indicate that dietary NO3− supplementation may acutely reduce blood pressure, and that this effect may be maintained for at least 15 days if supplementation is continued. 

Year:

2010

Link:

https://doi.org/10.1152/ajpregu.00206.2010 

Study 23

Study type: 

Randomised unblinded crossover trial

Dose:

Participants were assigned either:

1. 200mL of beetroot juice (with ~800mg of nitrate) and 40 minutes of moderate-intensity aerobic exercise

2. 200mL of low-nitrate fruit soda and the same exercise 

3. 200mL of water (insignificant nitrate) and no exercise.

Participants:

14 non-hypertensive obese males

Duration:

Acute (24 hours)

Results:

Compared to the control, supplementation with beetroot juice (dietary nitrate) was associated with a reduction in systolic ambulatory blood pressure (-5.3 mmHg) up to 6 hours after ingestion and moderate-intensity aerobic exercise. Beetroot juice supplementation was also associated with a significantly higher plasma nitric oxide concentration up to 1 hour after ingestion.

The authors concluded that inorganic nitrate may have important therapeutic applications to decrease the blood pressure response to exercise when individuals have an increased cardiovascular risk.

Year:

2019

Link:

https://pubmed.ncbi.nlm.nih.gov/30787659/ 

Study 25

Study type: 

Randomised, double-blind, placebo-controlled crossover trial

Dose:

500 mL/day of either nitrate-rich beetroot juice (containing 5.1 mmol of nitrate/day) or placebo (a drink with negligible nitrate content

Participants:

7 men aged 19 to 38

Duration:

6 days

Results:

Overall, systolic and diastolic was significantly lower after 6 days of nitrate supplementation (-7/7 mmHg). Relative to the placebo, nitrate supplementation was associated with reductions in systolic blood pressure (-5 mmHg), diastolic blood pressure (-2 mmHg) and mean arterial pressure (-2 mmHg).

Year:

2010

Link:

https://doi.org/10.1152/japplphysiol.00046.2010 

Study 26

Study type: 

Randomised, double-blind, placebo-controlled crossover trial

Dose:

0.11 mmol of nitrate per kg of body weight (a body mass-normalised moderate dose of nitrate) via beetroot juice.

Participants:

11 patients with peripheral artery disease

Duration:

Acute (∼1 hour)

Results:

Compared to the placebo, dietary nitrate supplementation was associated with reductions in peripheral and central systolic blood pressure (−4.7 mmHg and −8.2 mmHg, respectively) and significant increases in serum nitrate/nitrite level.

The authors concuded that acute, body mass-normalised, moderate doses of dietary nitrate may improve blood pressure and nitric oxide bioavailability.

Year:

2021

Link:

https://doi.org/10.1152/ajpregu.00121.2021 

Study 27

Study type: 

Randomised crossover trial

Dose:

∼400mg of nitrate at lunch, provided through nitrate-rich vegetables or beetroot juice supplementation

Participants:

15 healthy men and women (aged 24 on average)

Duration:

1 week

Results:

Nitrate-rich vegetables and beetroot juice supplementation were associated with increases in plasma nitrate concentrations and reductions in mean systolic and diastolic blood pressure throughout both intervention periods (∼2.5 hours after lunch).

Year:

2020

Link:

https://doi.org/10.1016/j.jand.2020.02.014 

Study 28

Study type: 

Systematic review and meta-analysis

Intervention under study:

Dietary inorganic nitrate (with doses ranging from 150 to 1000mg over a treatment range from 7 to 168 days).

Outcome under study:

Effect of repeated administrations of inorganic nitrate on blood pressure and arterial stiffness.

Studies included:

47 randomised controlled trials, including 1101 participants (including healthy, overweight, hypertensive, diabetic and hypercholesterolemic individuals, and patients with heart failure and peripheral artery disease).

Results:

The results found that inorganic nitrate supplementation was associated with an overall beneficial effect on blood pressure. Repeated (≥ 3 days) administrations of inorganic nitrates were associated with reductions in peripheral and central blood pressure.

Year:

2020

Link:

https://doi.org/10.1097/HJH.0000000000002524 

Study 29

Study type: 

Unblinded randomised controlled trial (pilot study)

Dose:

70mL of beetroot concentrate (containing ~300 to 400mg of nitrate)

Participants:

10 overweight men and women between the ages of 55 and 70

Duration:

21 days 

Results:

Supplementation with beetroot juice (dietary nitrate) was associated with a 10.2/3.1 mmHg reduction in blood pressure after 3 weeks of supplementation. 

Year:

2015

Link:

https://doi.org/10.1038/jhh.2014.114 

Study 1

Study type: 

Randomised double-blind cross-over trial

Intervention  & outcome:

Researchers studied the effects of acute beetroot ingestion on cycling performance in normobaric hypoxic conditions. The performance trials consisted of submaximal steady-state exercise for 15 minutes at 60% maximum work rate and, after a 5 minute break, a 16.1 km time trial at simulated altitude. During the time trial, participants were encouraged to complete the 16.1 km in the shortest time possible. The heart rate, peripheral oxygen saturation and respiratory variables were continuously monitored throughout each trial.

Dose:

The performance trials were preceded by ingestion of either 70mL of nitrate-rich beetroot juice (~5 mmol of nitrate) or a placebo (nitrate-depleted beetroot juice) 3h before exercise.

Participants:

9 competitive amateur male cyclists (aged 28 on average)

Duration:

Acute

Results:

A single dose of beetroot juice was associated with reduced oxygen cost of steady-state exercise and enhanced 16.1-km time trial performance at simulated altitude. 8 of the 9 participants were quicker during the beetroot trial than during the placebo trial. Beetroot juice was associated with a 2.9% performance improvement compared with baseline (1716 s at baseline; 1664 s after beetroot) with a medium effect size. Performance after beetroot ingestion was significantly improved compared with the placebo (1702 s after placebo). Performance was not different between baseline and placebo trials. 

Year:

2014

Link:

https://doi.org/10.1249/MSS.0b013e3182a1dc51 

Study 2

Study type: 

Systematic review

Intervention under study:

Dietary nitrate supplementation

Outcome under study:

Muscular power, velocity of contraction and muscular endurance during weightlifting in healthy adults

Studies included:

4

Results:

2 of the 4 studies included in the review indicate that nitrate supplementation may increase aspects of upper body exercise performance (i.e. bench press): there were associations with increases in mean power, velocity of contraction and number of repetitions to failure. Another study observed an increase in the number of repetitions to failure during back squats.

Year:

2020

Link:

https://doi.org/10.3390/nu12082227 

Products Containing Beetroot

L-CITRULLINE SCIENTIFIC STUDIES

We have summarised some of the most interesting scientific studies on L-citrulline.

It is important to note that a decrease between 5 and 12 mmHg of systolic blood pressure and between 5 and 6 mmHg of diastolic blood pressure is associated with a 14–38% risk reduction in stroke and a 21% risk reduction of death due to coronary disease.

Study 1

Study type: 

Randomised controlled trial

Participants:

12 young adults with normal blood pressure

Dose: 

3g of citrulline tablets per day

Duration:

1 week

Results:

Citrulline consumption was associated with a 6% reduction in systolic blood pressure and a 14% reduction in diastolic blood pressure.

Year:

2016

Link:

https://doi.org/10.1007/s00421-016-3418-7 

Study 2

Study type: 

Randomised controlled trial

Participants:

41 obese postmenopausal women

Duration:

8 weeks

Results:

L-citrulline supplementation was associated with significant reductions in blood pressure.

Year:

2015

Link:

https://doi.org/10.1139/apnm-2015-0465  

Study 3

Study type: 

Randomised controlled trial

Dose:

3g per day

Participants:

Heart failure patients

Duration:

2 months

Results:

L-citrulline supplementation was associated with significant reductions in systolic and diastolic arterial blood pressure.

Year:

2015

Link:

https://doi.org/10.1139/apnm-2015-0465  

Study 4

Study type: 

Systematic review

Intervention under study:

Oral supplementation with L-citrulline

Studies reviewed:

8 randomised controlled trials

Results:

The results suggest that L-citrulline supplementation may reduce systolic blood pressure (-4 mmHg). A significant reduction in diastolic blood pressure was observed only in the studies that used doses greater than 6 g of L-citrulline per day.

Year:

2019

Link:

https://pubmed.ncbi.nlm.nih.gov/30788274/ 

Study 1

Study type: 

Randomised controlled trial

Dose:

6 g L-citrulline-malate 2 h prior exercise

Participants:

17 male pre-professional cyclists

Duration:

Acute (before and after a 137-km cycling race)

Results:

After the cycling race, growth hormone levels were higher among participants taking L-citrulline malate than among participants in the control group. L-citrulline supplementation was also associated with higher levels of arginine-derived metabolites such as nitrite, creatinine, ornithine and urea.

Year:

2010

Link:

https://doi.org/10.1007/s00421-010-1509-4 

Study 2

Study type: 

Randomised placebo-controlled crossover trial

Dose:

2.4g of L-citrulline for 7 days and 2.4 g of L-citrulline 1h before a 4-km cycling time trial on day 8.

Participants:

22 athletically-trained males

Duration:

8 days

Results:

Compared to the placebo, L-citrulline supplementation was associated with a 1.5% reduction in the time taken to complete a 4-km cycling time trial. It was also associated with significant increases in plasma L-arginine levels.

Year:

2016

Link:

https://doi.org/10.1186/s12970-016-0117-z  

Study 3

Study type: 

Systematic review

Intervention under study:

L-citrulline supplementation before exercise

Studies reviewed:

13 studies comprising 206 participants

Results:

The results show a correlation between citrulline supplements and significant reductions in the rate of perceived exhaustion during physical activity and muscle soreness 24h and 48h after exercise.

The results suggest that athletes may benefit from ingesting either L-citrulline alone or 1h before exercise to resist fatigue or relieve muscle soreness.

Year:

2021

Link:

https://doi.org/10.1016/j.jshs.2020.02.003 

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