Type "testosterone booster" and you'll find hundreds of products promising more energy, more muscle, and more desire. Two teams of urologists did what no one does: they took the products, listed their ingredients, and searched the studies. The result comes down to one sentence: most do nothing, and some do the opposite.
This guide explains how testosterone really declines with age, what these two reviews found, which daily levers have clinical trials, then what each plant and mineral in our catalog has actually shown: ashwagandha, tribulus, maca, zinc and vitamin D, one by one, with the results that work in our favor and those that don't.
The decline. The Baltimore Longitudinal Study, 890 men, measures a decline of 0.124 nmol/L per year, just under 1% per year, independent of disease, and a decline with weight gain. Hypogonadism rates in 20% of men after age 60, 30% after 70, 50% after 80. The boosters. Of 50 products analyzed, 90% claim to increase testosterone, 24.8% have data to support it. Of 52 studies and 27 boosters, most fail.
What has data. Sleep: one week at five hours per night, 10 to 15% less testosterone. Weight loss: weight loss increases it.Ashwagandha, modest positive effect, fragile evidence. What doesn't have data. Tribulus and maca do not increase testosterone; they act on sexual function and desire. Zinc only in case of deficiency. Vitamin D, no. Low testosterone is diagnosed by morning blood test and treated with a doctor.
How testosterone really declines
Testosterone and SHBG were measured in preserved samples from 890 men in the Baltimore Longitudinal Study on Aging. After correction for a dating effect deemed artifactual, significant longitudinal effects independent of age were observed on testosterone and free testosterone index, with an average variation of minus 0.124 nmol/L per year. Testosterone, but not free testosterone index, also decreased with body mass index. According to total testosterone criteria, the incidence of hypogonadal levels reached approximately 20 percent of men over 60, 30 percent after 70 and 50 percent after 80. The authors conclude an age-related decline, independent of health status.
Harman SM, Metter EJ, Tobin JD, Pearson J, Blackman MR. J Clin Endocrinol Metab 2001;86(2):724-731. DOI: 10.1210/jcem.86.2.7219
Three things in this result. The decline is real and continuous : 0.124 nmol/L per year on testosterone that typically ranges between 12 and 30 nmol/L in adults, or just under 1% per year. It is independent of diseases, making it an effect of aging itself. And it is worsened by weight : at the same age, the higher the body mass index, the lower the total testosterone. This is the first lever, and it's not in a capsule.
Testosterone that declines with age is normal. Testosterone low with symptoms,hypogonadism, is a disease. The distinction is made by blood testing and by a doctor, and it changes everything: the first is lived with, the second is treated. Section 5 details the signs and testing.
The boosters: what two reviews say
Fifty testosterone "booster" supplements found by Google search were evaluated for their active ingredients and claims, then the literature was searched for each component. Ninety percent of the products claimed to increase testosterone, 50 percent to improve libido, and 48 percent to increase strength. One hundred nine unique components were found, 8.3 per product on average. On PubMed, 24.8 percent of supplements had data showing a testosterone increase, 10.1 percent had data showing a decrease, 18.3 percent had data showing no effect, and no data existed for 61.5 percent. The products contained in median 1,291 percent of the recommended intakes for vitamin B12 and 272 percent for zinc; thirteen exceeded the upper safety limit for zinc, vitamin B3, or magnesium.
Clemesha CG, Thaker H, Samplaski MK. World J Mens Health 2020;38(1):115-122. DOI: 10.5534/wjmh.190043
The second review, published in 2023 in theInternational Journal of Impotence Research by a team of urologists from six countries, did the opposite: start from the studies. It brought together 52 studies on 27 proposed boosters, in athletes, men with late-onset hypogonadism, infertile men, and healthy men, with a single criterion, the increase in total testosterone versus placebo. Its conclusion: most fail. The exceptions are few and specific. Ashwagandha is classified there as possibly effective in healthy men, alongsideEurycoma longifolia. Tribulus, four studies, maca, two studies, zinc and magnesium, five studies, and vitamin D, ten studies, are among those that fail.
A "booster" with eight ingredients, none of which has data, is no more effective than a single ingredient that does. And doses of zinc and B vitamins that exceed safety limits are not a sign of potency; it's a sign that the manufacturer didn't read the same studies as the urologists. The rest of this article discusses only isolated ingredients, with their own data.
The levers that have trials
Sleep
A research letter published in JAMA in 2011 by the University of Chicago had healthy young men sleep five hours per night for one week, in the laboratory, and measured their testosterone before and after. Result: a decrease in daytime testosterone of 10 to 15%, equivalent to ten to fifteen years of aging according to the Baltimore slope, in seven nights. This is, by far, the most powerful modifiable factor, and it works in both directions. Our cortisol guide details how to regulate your sleep clock.
Weight
The Baltimore study shows that total testosterone decreases with body mass index. Adipose tissue converts testosterone to estrogens, and excess abdominal fat lowers production. A meta-analysis published in 2024 in the World Journal of Men's Health reminds us that weight loss significantly raises testosterone, and measures, over 12 studies and 345 obese men, an improvement in sperm concentration and mobility as well as a decrease in sperm DNA fragmentation after weight loss. In an overweight man, weight loss is the second lever, and it is more powerful than everything that follows.
The rest
Resistance training, alcohol, and chronic stress have documented effects on testosterone, in the expected direction, and they largely work through sleep and weight. We do not devote a section to them because we did not retain a meta-analysis on them here.
Plants and minerals, one by one
A systematic review of 32 randomized trials on 13 plants, published in Advances in Nutrition, identifies two extracts with positive effects on testosterone in men: fenugreek andashwagandha, root or root and leaf. It notes that only 9 out of 32 trials show a significant increase, that 6 out of 32 have a low risk of bias, and that half of the trials involve men under 40 years old. A review in the Journal of Ethnopharmacology reports an increase of 143 ng/dL with 5 g of powdered root per day for 12 weeks in men with oligozoospermia. The 2023 booster review classifies it as possibly effective in healthy men. Real effect, modest, evidence still fragile: that's the most honest we can say, and it's already more than for everything else.
It's the best-selling plant for testosterone, and it's the one with the clearest reviews. The 2023 review includes four studies and ranks it among the boosters that fail. The review in the Journal of Ethnopharmacology, titled "beyond tribulus," concludes that its use is not scientifically supported to increase testosterone in men, while noting that it could have favorable effects on sperm parameters in infertile men. We sell tribulus, at 471 mg standardized to 90% saponins, and we say it clearly: it's a plant for sexual function and fertility, not a testosterone plant.
A randomized double-blind trial published in Andrologia gave 1.5 or 3 g of gelatinized maca or placebo for 12 weeks to men aged 21 to 56, specifically to verify whether its effect on desire was mediated by hormones. Sexual desire improved from the eighth week; testosterone and estradiol did not change, and analysis shows an effect on desire independent of both mood and hormones. Both systematic reviews confirm the absence of hormonal effect. Maca acts on desire, not on testosterone. Our organic maca provides 1.28 g per day.
The reference study, published in Nutrition in 1996 by the Wayne State team, restricted dietary zinc in healthy young men for 20 weeks: their testosterone dropped from 39.9 to 10.6 nmol/L. In older men with marginal deficiency, six months of zinc gluconate raised it from 8.3 to 16.0. A 2022 systematic review confirms that deficiency lowers testosterone and that supplementation raises it, with an effect that depends on baseline status. But the booster review ranks zinc among those that fail in men without deficiency. Zinc corrects a deficiency, it doesn't boost anything. Our zinc guide details the signs of deficiency.
It's the most studied booster in the 2023 review, ten studies, and it ranks it among those that fail to increase total testosterone. Vitamin D deficiency should be corrected for other reasons—bone, muscle, immunity—and we sell vitamin D3 for those reasons, not for testosterone.
| Ingredient | Testosterone | What it really does |
|---|---|---|
| Ashwagandha | Modest positive effect, two reviews | Stress, sleep, and a signal on testosterone |
| Tribulus | No | Sexual function, sperm parameters |
| Maca | No, verified in a dedicated trial | Sexual desire, from 8 weeks onward |
| Zinc | Yes if deficient, no otherwise | Correct a deficiency |
| Vitamin D | No, ten studies | Bones, muscles, immunity |
When to consult, and how to get tested
Signs of low testosterone are well known: decrease in desire and morning erections, fatigue that doesn't improve with rest, loss of muscle mass and strength, abdominal fat gain, low or irritable mood, concentration difficulties. None is specific: fatigue, mood, and weight have many other causes, including sleep and stress, covered in our article on adrenal fatigue. It is the sexualsigns, combined with others, that provide direction.
A blood test in the morning between 7 and 10 a.m., fasting, when testosterone is at its peak, and repeated a second time if it is low, because it varies from day to day. A doctor interprets it with free testosterone or SHBG, and looks for a cause. An isolated afternoon test means nothing, and a low result is not treated with a plant: hypogonadism requires medical management, and hormone therapy, when indicated, is a prescription with monitoring.
The reasonable protocol
1.28 g of maca root per day, from organic farming. The randomized trial inAndrologia measured an improvement in sexual desire from the eighth week, independent of mood and without changes in testosterone or estradiol. Four capsules per day, 30 days; eight weeks before judging results.
View Organic MacaMaca does not increase testosterone. Not recommended without medical advice in cases of hormone-dependent conditions.
Choose what fits you best: the answer appears right below.
One week at five hours of sleep costs 10 to 15% of testosterone, equivalent to ten to fifteen years. No capsule can compensate for that. Seven hours regularly for three weeks, then reassess. If fatigue and desire don't return, move to profile C.
Testosterone drops with body mass index and rises with weight loss, which also improves semen quality according to the 2024 meta-analysis. Resistance training, adequate protein, moderate caloric deficit. It's the most powerful lever after sleep, and an eight-ingredient booster without data won't replace it.
Sexual signs associated with loss of strength, despite adequate sleep, are those that point to low testosterone. Blood test in the morning between 7 and 10 AM, repeated if low, and medical consultation. This is not a supplement situation: hypogonadism is diagnosed and treated medically.
In a healthy man who is well-rested and normal weight, systematic reviews find almost nothing that increases testosterone. Ashwagandha has a modest positive effect and fragile evidence; it's the only one. The rest acts on libido, like maca, or on nothing. Keep your money for sleep and the gym.
This test provides guidance, it does not replace professional medical advice.
Frequently asked questions
The decline
Does testosterone really decline with age?
Yes, and it's measured over the long term. The Baltimore longitudinal study, published in the Journal of Clinical Endocrinology and Metabolism, followed 890 men and found a decline in total testosterone of 0.124 nmol/L per year, independent of disease and medication—roughly less than 1% per year for an adult male. It also found that testosterone declines with body mass index. As a result: testosterone levels in the hypogonadism range in approximately 20% of men over 60, 30% after 70, and 50% after 80.
What really lowers testosterone daily?
Sleep deprivation first: a research letter published in JAMA reports that one week of nights limited to five hours in healthy young men reduced daytime testosterone by 10 to 15%, equivalent to ten to fifteen years of aging. Overweight next: the Baltimore study shows that testosterone declines with body mass index, and a 2024 meta-analysis confirms that weight loss raises it significantly while improving sperm parameters in obese men. Alcohol, chronic stress, and certain medications add to this.
Boosters and herbal supplements
Do testosterone boosters work?
Most don't. A systematic review published in theInternational Journal of Impotence Research examined 52 studies on 27 proposed boosters and concluded that most fail to increase total testosterone. Another, published in the World Journal of Men's Health, analyzed 50 products sold online: 90% claim to increase testosterone, but only 24.8% contain ingredients with supporting data, 10.1% contain ingredients associated with a decrease, and 61.5% have no data. Thirteen products exceeded safety limits for zinc, vitamin B3, or magnesium.
Does tribulus increase testosterone?
No in healthy men. The 2023 systematic review includes four studies on tribulus and ranks it among the boosters that fail. A review in the Journal of Ethnopharmacology concludes that its use is not scientifically supported for increasing testosterone, while noting it could have favorable effects on sperm parameters in infertile men. Tribulus is an herb for sexual function and fertility, not for testosterone, and we prefer to say so since we sell it.
Does maca increase testosterone?
No, and that's precisely what one trial wanted to verify. A randomized double-blind trial published in Andrologia gave 1.5 or 3 g of gelatinized maca or placebo to men aged 21 to 56 for 12 weeks: sexual desire improved from the eighth week onward, but testosterone and estradiol remained unchanged, and the effect on desire was independent of mood as well as hormones. Maca acts on desire, not on testosterone. Both systematic reviews confirm the absence of hormonal effect.
Does ashwagandha increase testosterone?
It is the plant in the catalog with the best data. A systematic review of 32 randomized trials published in Advances in Nutrition identifies two extracts with positive effects on testosterone in men, fenugreek and ashwagandha, noting that only 9 out of 32 trials show a significant increase and that 6 out of 32 have a low risk of bias. The 2023 review classifies it as possibly effective in healthy men. A review in the Journal of Ethnopharmacology reports an increase of 143 ng/dL with 5 g of powdered root over 12 weeks in men with oligozoospermia. A real, modest effect, with still fragile evidence.
Does zinc increase testosterone?
Only if it's deficient. The landmark study, published in Nutrition in 1996, restricted dietary zinc in healthy young men for 20 weeks: their testosterone dropped from 39.9 to 10.6 nmol/L. In older men with marginal deficiency, six months of zinc gluconate raised it from 8.3 to 16.0 nmol/L. A 2022 systematic review confirms that deficiency lowers testosterone and supplementation raises it, with an effect that depends on baseline status. But the 2023 testosterone booster review ranks zinc among those that fail in men without deficiency. Zinc corrects a deficiency, it doesn't boost anything.
Does vitamin D increase testosterone?
Not in men whose status is normal. The 2023 systematic review examined the most studies on vitamin D, ten in total, and ranks it among the boosters that fail to increase total testosterone. Vitamin D deficiency is corrected for other reasons—bones, muscles, immunity—not for testosterone.
Consult
What are the signs of low testosterone?
A decrease in sexual desire and morning erections, fatigue that doesn't improve with rest, loss of muscle mass and strength, abdominal fat gain, low or irritable mood, concentration problems. None of these signs is specific: fatigue, mood, and weight gain have many other causes, including sleep and stress. A picture combining several of these signs, particularly sexual signs, warrants a consultation, not a supplement.
How do you know if you have low testosterone?
Through a blood test, in the morning between 7 and 10 a.m., fasting, when testosterone peaks, and repeated a second time if it's low, because it varies from day to day. A doctor interprets it with free testosterone or SHBG, and looks for a cause. An isolated measurement in the afternoon means nothing. And a low result is not treated with a plant: hypogonadism is a disease that requires medical management.
What to remember about testosterone and supplements?
That testosterone decreases by just under 1% per year and with weight gain. That most boosters do nothing, according to two systematic reviews. That sleep and weight matter more than any capsule. That ashwagandha is the only plant in the catalog with positive, modest data. That tribulus and maca act on sexual function and desire, not on the hormone. That zinc only matters in case of deficiency and that vitamin D doesn't matter. And that low testosterone is diagnosed by a blood test and treated by a doctor.
Glossary
- Total testosterone
- All circulating testosterone, bound or free; the criterion of booster reviews, expressed in nmol/L or ng/dL.
- SHBG
- Protein that binds testosterone in the blood; its increase with age reduces the free fraction, hence the free testosterone index.
- Hypogonadism
- Insufficient testosterone production with symptoms, confirmed by at least two morning measurements; a disease, not an age-related decline.
- Longitudinal study
- A study that follows the same people over time, like the Baltimore study; more reliable than comparing different ages at one point in time.
- Systematic review
- Exhaustive and critical research of all studies on a question; the two booster reviews are examples of this.
- Oligozoospermia
- Sperm concentration below normal; the population of several trials on plants and fertility.
- Saponins
- Compounds in tribulus on which extracts are standardized; their content does not change the absence of effect on testosterone.
Sources
The studies cited below were identified via PubMed.
- Harman SM, Metter EJ, Tobin JD, Pearson J, Blackman MR. Longitudinal effects of aging on total and free testosterone in healthy men: the Baltimore Longitudinal Study. Journal of Clinical Endocrinology and Metabolism, 2001;86(2):724-731. DOI
- Leproult R, Van Cauter E. Effect of one week of sleep restriction on testosterone in healthy young men. JAMA, 2011;305(21):2173-2174. DOI
- Santi D, Greco C, Barbonetti A, Simoni M, Maggi M, Corona G. Weight loss as a therapeutic option to restore fertility in obese men: meta-analysis. World Journal of Men's Health, 2025;43(2):333-343. DOI
- Clemesha CG, Thaker H, Samplaski MK. The composition and claims of "testosterone booster" supplements are not supported by academic literature. World Journal of Men's Health, 2020;38(1):115-122. DOI
- Morgado A, Tsampoukas G, Sokolakis I, Schoentgen N, Urkmez A, Sarikaya S. Do "testosterone boosters" really increase total testosterone? Systematic review. International Journal of Impotence Research, 2024;36(4):348-364. DOI
- Smith SJ, Lopresti AL, Teo SYM, Fairchild TJ. Review of the effects of herbal plants on testosterone concentrations in men: systematic review. Advances in Nutrition, 2021;12(3):744-765. DOI
- Santos HO, Howell S, Teixeira FJ. Beyond tribulus: effects of herbal therapies on testosterone, sperm, and the prostate. Journal of Ethnopharmacology, 2019;235:392-405. DOI
- Gonzales GF, Córdova A, Vega K, et al. Effect of Lepidium meyenii (maca) on sexual desire and its lack of relationship with serum testosterone in healthy adult men. Andrologia, 2002;34(6):367-372. DOI
- Prasad AS, Mantzoros CS, Beck FW, Hess JW, Brewer GJ. Zinc status and serum testosterone in healthy adults. Nutrition, 1996;12(5):344-348. DOI
- Te L, Liu J, Ma J, Wang S. Correlation between serum zinc and testosterone: systematic review. Journal of Trace Elements in Medicine and Biology, 2023;76:127124. DOI
