Testosterone

Testosterone: A Comprehensive Reference in Nutrition and Natural Health

1. Definition and Overview

Testosterone is the primary male hormone regulating sex differentiation, producing male sex characteristics, spermatogenesis, and fertility. Chemically, it is a steroid hormone derived from cholesterol. In males, the majority of testosterone is synthesized in the Leydig cells of the testes, while in females, smaller amounts are produced by the ovaries and adrenal glands; although testosterone is often considered a male hormone, it plays an essential role in both sexes, contributing to a range of physiological processes beyond sexual differentiation, including muscle mass maintenance, bone density, mood regulation, and metabolic function.

Testosterone's effects are first seen in the fetus. During the first six weeks of development, the reproductive tissues of males and females are identical. Around week 7 in utero, the SRY gene on the Y chromosome initiates development of the testicles. Sertoli cells from the testis cords eventually develop into seminiferous tubules, and Sertoli cells produce a Müllerian-inhibiting substance (MIS), which leads to the regression of structures that would otherwise become the fallopian tubes, uterus, and upper vaginal segment.

2. Physiology and Body Systems Involved

2.1 The Hypothalamic–Pituitary–Gonadal (HPG) Axis

The hypothalamic–pituitary–gonadal axis regulates testosterone levels and gonadal function. The hypothalamus secretes gonadotropin-releasing hormone (GnRH), which travels through the hypothalamohypophyseal portal system to the anterior pituitary, stimulating secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These gonadotropic hormones circulate in the bloodstream and act on receptors in the gonads. LH acts on Leydig cells to increase testosterone production. Testosterone limits its own secretion via negative feedback.

Both men and women also produce weak-acting androgens in the zona reticularis of the adrenal glands.

2.2 Conversion and Receptor Action

Testosterone can be converted in the periphery to a more active form — dihydrotestosterone (DHT) — via 5-alpha-reductase, or to estradiol via aromatase. Testosterone and DHT bind to intracellular receptors and regulate protein expression. Androgen effects are mediated by the androgen receptor (AR, also denoted NR3C4), which is a 110 kDa protein localized to the nucleus and cytoplasm.

2.3 Key Physiological Roles

The Leydig cells of the testes are the main source of testosterone in men; although testosterone is frequently regarded as a male hormone, it is essential for many physiological processes outside of sexual differentiation, including maintaining muscle mass, bone density, mood regulation, and metabolic processes. In puberty, a surge in sex hormones, including testosterone and estrogen, drives the development of secondary sexual characteristics.

The testes serve as the primary source of androgens and the site of spermatogenesis, with their development and function governed by hormonal actions via endocrine and paracrine pathways. Male fertility hinges on the availability of testosterone, a cornerstone of spermatogenesis, while FSH signaling is indispensable for the proliferation, differentiation, and proper functioning of Sertoli and germ cells.

2.4 Testosterone in Women

Testosterone, a steroid hormone primarily synthesized in the testes in males and in smaller quantities in the ovaries and adrenal glands in females, is essential for a wide range of physiological processes. In women, testosterone contributes to libido, bone density, muscle maintenance, and energy regulation, although at substantially lower circulating concentrations than in men.

3. Testosterone Deficiency: Presentation and Clinical Associations

Testosterone deficiency can reduce the quality of life due to decreased libido, impotency, infertility, fatigue, depressed mood, decreased concentration and memory, and sleep disorders in males. Among patients with chronic diseases, including diabetes mellitus, hypertension, dyslipidemia, and chronic obstructive pulmonary disease, 30% also have testosterone deficiency.

Growing evidence indicates a secular, age-independent decline in testosterone levels across populations, a trend associated with reduced fertility, metabolic and cardiovascular dysfunction, mood disturbances, and impaired quality of life. From a medical perspective, low testosterone levels (clinically diagnosed as hypogonadism) are strongly associated with various chronic maladies including metabolic syndrome, cardiovascular disease, and overall mortality. Psychologically and socially, low testosterone levels are linked to increased rates of depression, anxiety, reduced motivation, and lower quality of life.

4. Contributing and Associated Factors

4.1 Obesity and Metabolic Syndrome

Not only nutrient scarcity but also excess, as found in obesity, is associated with hypogonadism and infertility. Several lines of evidence have demonstrated that the persistent induction of pro-inflammatory cytokines in obese individuals ("low-grade inflammation") causally contributes to low testosterone levels by impairing hypothalamic function.

4.2 Acquired and Behavioral Risk Factors

While an underlying congenital cause should always be considered in young men with hypogonadism, acquired conditions such as obesity, diabetes, anabolic steroid or illicit drug use have all been associated with low testosterone levels.

Unhealthy habits, such as obesity, stress, alcohol abuse, smoking, excess caffeine intake, and a lack of exercise are associated with low levels of testosterone. Alcohol has been demonstrated to reduce testosterone levels by affecting the testis and the hypothalamic-pituitary-testicular axis according to in vitro and in vivo studies. However, in human studies, alcohol abuse has various effects on reducing testosterone, and these effects depend on the amount and duration of alcohol intake.

4.3 Environmental and Modern Lifestyle Factors

While aging and genetic factors play a role, a wide range of modifiable influences — including obesity, physical inactivity, unhealthy dietary patterns, chronic stress, poor sleep, and exposure to endocrine-disrupting chemicals or other environmental stressors — appear to contribute substantially to the secular decline in testosterone.

Rising rates of obesity and metabolic disorders, exposure to endocrine-disrupting chemicals (EDCs) like phthalates or microplastics, sedentary lifestyles, unhealthy dietary patterns, and chronic psychosocial stress have all been implicated. It seems that no single factor alone accounts for the observed reductions, suggesting a cumulative burden of metabolic, environmental, and behavioral stressors as the driving force.

4.4 Overtraining and Extreme Caloric Deficit

Almost any evolutionarily relevant environmental challenge such as cold, starvation, or stress, which requires prioritization of energy distribution, provokes reduction in circulating testosterone levels. Strenuous endurance exercise yielding an imbalance between energy consumption and expenditure (male exercising syndrome) is associated with hypogonadism and subfertility. Low testosterone levels under these conditions can be considered an adaptive response to reduce the energetic burden of sex hormone-driven biological functions.

5. Dietary and Lifestyle Factors

5.1 Physical Activity

A positive correlation was found between leisure-time physical activity and testosterone levels, particularly in the older group of healthy men aged 19–32 years. Multiple regression analyses in young men aged 18–22 revealed that hypertrophy training, sunlight exposure over 60 minutes, and supplement use were positive predictors of testosterone. Conversely, daily carbonated beverage consumption, tobacco use, and sleep deprivation were significant negative correlates of testosterone in the same population.

5.2 Body Composition and Diet Quality

Free testosterone concentration in blood was negatively correlated with body fat content and positively correlated with the percentage of energy, protein, fat, sodium, and folic acid requirements met in a cross-sectional study of healthy young men.

Lifestyle factors, including diet, physical activity, and stress management, play a crucial role in managing hormonal health. A diet rich in fruits, vegetables, whole grains, lean proteins, and healthy fats can help maintain optimal cardiovascular and hormonal function. Specific nutrients, such as omega-3 fatty acids, antioxidants, and fibre, have been shown to support heart health and reduce inflammation.

5.3 Sleep

A wide range of modifiable influences — including poor sleep — appear to contribute substantially to the secular decline in testosterone levels across populations. Evidence on the direction and magnitude of the sleep-testosterone relationship is mixed: one set of randomized controlled studies concluded that sleep restriction does not adversely affect plasma testosterone levels in healthy young men, and confirmatory studies have been recommended to ascertain the influence of sleep duration and quality on testosterone concentrations in men throughout life.

5.4 Stress Management

Professional guidelines emphasize lifestyle-based strategies — such as weight loss, dietary changes, physical activity, sleep interventions, and stress management — as first-line approaches in the context of testosterone decline. Chronic psychological and physiological stress elevates cortisol, which can suppress gonadal testosterone production through actions on the HPG axis.

6. Nutrients Studied in Relation to Testosterone

6.1 Zinc

Zinc is a vital trace element for normal function of the living system; in males, zinc is involved in various biological processes, an important function of which is as a balancer of hormones such as testosterone. After analysis of 38 papers including 8 clinical and 30 animal studies in a 2022 systematic review, researchers concluded that zinc deficiency reduces testosterone levels and zinc supplementation improves testosterone levels.

Scientific evidence: The effect degree of zinc on serum testosterone may vary depending on basal zinc and testosterone levels, zinc dosage form, elementary zinc dose, and duration. Among supplements, the evidence mostly supports vitamin D and zinc, followed by magnesium, for benefiting testosterone production. However, supplementing with a vitamin or mineral is likely to help only if the individual suffers from a deficiency or insufficiency. Correcting a deficiency or insufficiency is more likely to raise testosterone levels if they are low. In clinical trials, zinc supplementation in deficient men has been associated with significant increases in testosterone and luteinizing hormone.

6.2 Vitamin D

Vitamin D helps regulate testosterone levels. Ideally, an individual would produce all the vitamin D they need through sunlight exposure, but those living far from the equator, with dark skin, or spending most time indoors may need to supplement dietary intake.

Scientific evidence (mixed): Mechanistically, vitamin D exhibits essential roles in the testis and prostate; however, a 2020 PubMed review found no apparent evidence to support the use of vitamin D supplementation to increase testosterone levels and to improve clinical outcomes related to the male reproductive system. Examine.com notes that the benefit of vitamin D supplementation for testosterone appears primarily in men who are vitamin D deficient, with limited effect in replete individuals.

6.3 Magnesium

Among commonly discussed supplements, the evidence for magnesium, while present, is ranked below that for zinc and vitamin D. A 2011 study published in the International Journal of Andrology (Maggio et al.) investigated the association between magnesium and anabolic hormones, including testosterone, in older men and found a positive correlation between magnesium status and testosterone concentrations.

7. Herbal and Botanical Ingredients

7.1 Ashwagandha (Withania somnifera)

Traditional use: Ashwagandha is a foundational herb of Ayurvedic medicine, originating in South Asia. Traditionally used as a rasayana (rejuvenating tonic), it was administered as a root powder preparation in warm milk or ghee for purposes of enhancing vitality, reproductive capacity, and stress resilience in both men and women.

Scientific evidence: Four randomized controlled trials examined the effects of ashwagandha on testosterone concentrations. Two used the patented root extract KSM-66® (standardized to 5% withanolides) and two used Shoden® (standardized to 35% withanolide glycosides). Three studies used a randomized, double-blind, placebo-controlled design and one used a crossover design. A total of 197 male participants were recruited, with ages ranging from 18 to 70 years. Three of the four studies demonstrated positive effects of ashwagandha supplementation on testosterone concentrations in men, while one study showed no significant effect.

One positive study examined the effect of KSM-66® on 46 infertile men with a mean age of 34 years. Supplementing with 675 mg/day was associated with a significant increase in testosterone concentrations (17.3% increase) after 90 days compared with the placebo group (3.8% increase), reaching statistical significance (P < 0.01).

The main findings of a 2021 systematic review of 32 clinical trials on 13 herbs indicate that two herbal extracts — fenugreek seed extracts and ashwagandha root and root/leaf extracts — have positive effects on testosterone concentrations in men. Overall, evidence is considered promising but preliminary, with limitations including small sample sizes, heterogeneous populations, and varied extract standardizations.

7.2 Fenugreek (Trigonella foenum-graecum)

Traditional use: Fenugreek seeds have been used for centuries in traditional Ayurvedic, traditional Chinese, and Mediterranean herbal medicine as a galactagogue, digestive tonic, and general vitality herb. In South Asian traditions, seeds were often consumed as decoctions or added to food preparations. Diosgenin, a steroidal saponin found in fenugreek seeds, has historically been associated with hormone-modulating activity.

Scientific evidence: A meta-analysis of clinical trials concluded that fenugreek extract has a significant effect on total serum testosterone, with results suggesting it affects serum total testosterone levels in males. A meta-analysis on fenugreek seed extract supplementation reported a significant increase in testosterone concentrations, including four randomized clinical trials, though it excluded studies with a duration shorter than four weeks. Moderate evidence supports the use of fenugreek to increase total testosterone and improve seminal parameters. Evidence quality is generally moderate, with most trials being industry-sponsored and of short duration.

7.3 Tribulus Terrestris

Traditional use: Tribulus terrestris has been used in traditional Ayurvedic medicine (as Gokshura) and traditional Chinese medicine as a tonic for kidney and liver function, and for reproductive vitality. In traditional Bulgarian and Eastern European folk medicine, the herb was used for male sexual complaints. Extracts were typically prepared from the fruit or aerial parts.

Scientific evidence: A systematic review on all tribulus studies examining testosterone in animals and humans concluded that the evidence indicated it is ineffective at increasing testosterone concentrations in humans. The use of Tribulus terrestris was not scientifically supported to improve serum testosterone levels in men in a focused review of studies published between 2002 and 2018. Some studies supporting a potential approximately 60–70 ng/dL increase in total testosterone following Tribulus supplementation in men with low baseline testosterone have been noted, but this occurred within a context of poor methodological quality. Despite inconclusive evidence as a testosterone booster, Tribulus terrestris presented advantageous effects for patients suffering from erectile dysfunction in three of five reviewed studies.

7.4 Eurycoma longifolia (Tongkat Ali / "Malaysian Ginseng")

Traditional use: Eurycoma longifolia Jack (Tongkat Ali or Malaysian ginseng) has been traditionally used for management of male sexual dysfunction and infertility. In Malaysia, one of the most popular herbs, Eurycoma longifolia Jack, from the Simaroubaceae family, also known traditionally as Tongkat Ali, has been reputed by Malays as a traditional remedy used as an adaptogen for vitality and energy and is well-known for its aphrodisiac activities. Traditionally used remedies for enhancing testosterone in men are water extracts of the roots of E. longifolia, from which a wide range of bioactive compounds have been isolated including phenolic compounds, polypeptides, diterpenoids, alkaloids, and quassinoids.

Scientific evidence: Male hypogonadism is a clinical disorder characterized by reduced serum testosterone in men. A 2022 systematic review and meta-analysis (PRISMA-guided) of clinical trials retrieved from PubMed, Scopus, Web of Science, Cochrane, Ovid/Embase, and Google Scholar included nine studies in the systematic review and five RCTs in the meta-analysis. A significant improvement in total testosterone levels after E. longifolia treatment was mostly reported in both healthy volunteers and hypogonadal men. Previous studies have shown properly-standardized Tongkat Ali to stimulate release of free testosterone, improve sex drive, reduce fatigue, and improve well-being. One randomized placebo-controlled study assessed stress hormones and mood state in 63 subjects screened for moderate stress and supplemented with standardized hot-water extract of Tongkat Ali root or placebo for 4 weeks. Evidence is moderate, with most trials involving relatively small samples and varying extract standardizations.

7.5 Mucuna pruriens

Traditional use: Mucuna pruriens (velvet bean) has been used in Ayurvedic medicine under the name Kapikacchu for centuries, primarily for neurological support, reproductive health, and as an aphrodisiac tonic. Seeds were traditionally processed into powders or decoctions to reduce the naturally occurring L-DOPA content's adverse effects while preserving therapeutic actions.

Scientific evidence: Moderate evidence supports the use of mucuna (Mucuna pruriens) to increase total testosterone and improve seminal parameters. Mucuna and ashwagandha have been classified as superior to some other herbal medicines such as Tribulus terrestris in potential testosterone-boosting capacity, based on comparative reviews of clinical evidence. Most human studies are small, and the proposed mechanism involves L-DOPA content modulating prolactin and dopamine pathways, which in turn may support LH secretion and testosterone production. Evidence remains preliminary and requires larger, well-controlled trials.

7.6 Nigella sativa (Black Seed)

Traditional use: Nigella sativa (black seed, black cumin) has been used in Islamic traditional medicine, as referenced in historical texts, for a wide array of ailments including male reproductive disorders. Seeds and their cold-pressed oil were traditionally administered internally.

Scientific evidence: A focused review of phytotherapeutic literature found that while Tribulus and maca were not scientifically supported to improve serum testosterone, moderate evidence supports the use of black seeds (Nigella sativa) to increase total testosterone and improve seminal parameters. Clinical evidence is limited to a small number of trials with modest sample sizes, and further large-scale RCTs are warranted.

7.7 Maca (Lepidium meyenii)

Traditional use: Maca root has been cultivated and consumed in the Andean highlands of Peru for over two thousand years. Indigenous Andean communities traditionally used maca as both a food staple and for enhancing fertility, energy, and stamina. It was commonly consumed in powdered or dried form or as a fermented beverage.

Scientific evidence: Scientific literature does not support the use of maca to improve serum testosterone levels in men. While some clinical trials report benefits for libido and sexual function, these effects appear to be independent of changes in circulating testosterone concentrations. Evidence for maca as a testosterone modulator is currently weak.

8. Evidence Summary and Strength Assessment

• Zinc: Moderate–strong evidence for restoring testosterone in deficient individuals. Weak evidence for raising testosterone above baseline in replete individuals.
• Vitamin D: Moderate evidence for an association between vitamin D status and testosterone; clinical trials supplementing vitamin D have shown mixed results, with some reviews finding no clear benefit in non-deficient men.
• Magnesium: Preliminary evidence for a positive association between magnesium status and testosterone, particularly in older men and athletes. Effect in replete individuals is unclear.
• Ashwagandha: Moderate evidence from multiple small RCTs; three of four human trials showed significant increases in testosterone, particularly in infertile and stressed men. Extract standardization is an important variable.
• Fenugreek: Moderate evidence from meta-analysis of clinical trials showing significant increases in total and free testosterone. Most trials are industry-sponsored and of short duration.
• Eurycoma longifolia (Tongkat Ali): Moderate evidence from a systematic review and meta-analysis of RCTs showing significant improvement in testosterone in both healthy and hypogonadal men. Extract standardization is critical.
• Tribulus terrestris: Weak evidence for testosterone elevation in humans; systematic reviews generally find it ineffective for this purpose, though some limited evidence exists for sexual function benefits.
• Mucuna pruriens: Moderate but preliminary evidence from small studies; may improve testosterone and seminal parameters, particularly in infertile men.
• Nigella sativa: Preliminary–moderate evidence from limited human trials; results are promising but require replication.
• Maca: Weak evidence for testosterone modulation; benefits for libido appear testosterone-independent.

In the broader literature, there are mixed results regarding the efficacy of herbal supplements in testosterone treatment. Some studies have demonstrated modest improvements in testosterone levels and related symptoms, while others showed no significant benefits compared to placebo.

9. Dietary Patterns and Specific Nutrients of Interest

In a cross-sectional study of healthy young men, free testosterone concentration was negatively correlated with body fat content and positively correlated with the percentage of energy, protein, fat, sodium, and folic acid requirements met. Higher intakes of cholesterol, folic acid, and vitamin A resulted in statistically significant reductions in cortisol levels, which may indirectly support a favorable testosterone-to-cortisol ratio.

Cholesterol serves as the biosynthetic precursor to all steroid hormones, including testosterone. Dietary fat — particularly saturated and monounsaturated fats from whole food sources — provides substrate for steroidogenesis. Very-low-fat diets have been associated in some research with lower androgen levels, though the evidence is not uniformly consistent across all populations and study designs.

References

• StatPearls: Physiology, Testosterone — NCBI Bookshelf
• Benefits of Testosterone Hormone in the Human Body: A Systematic Review — PMC (Cureus, 2025)
• Impact of Testosterone on Male Health: A Systematic Review — PMC
• The Regulation of Spermatogenesis by Androgens — PMC / NIH
• Physiology, Male Reproductive System — StatPearls / NCBI
• Late-onset hypogonadism: clinical evidence, biological aspects and evolutionary considerations — PMC
• Understanding the Secular Decline in Testosterone: Mechanisms, Consequences, and Clinical Perspectives — MDPI (2026)
• Low Testosterone in Adolescents & Young Adults — PMC / Frontiers in Endocrinology
• The Relationship between Testosterone Deficiency and Men's Health — PMC
• How Can You Increase Testosterone Naturally? — Examine.com
• Reviewing the Evidence on Vitamin D Supplementation in the Management of Testosterone Status — PubMed
• Correlation between Serum Zinc and Testosterone: A Systematic Review — ScienceDirect (Journal of Trace Elements in Medicine and Biology, 2022)
• Examining the Effects of Herbs on Testosterone Concentrations in Men: A Systematic Review — PMC
• Beyond Tribulus: The Effects of Phytotherapics on Testosterone, Sperm and Prostate Parameters — ScienceDirect
• Effects of Tribulus Supplementation on Erectile Dysfunction and Testosterone Levels in Men: A Systematic Review — MDPI Nutrients (2025)
• Effect of Fenugreek Extract Supplement on Testosterone Levels in Male: A Meta-Analysis of Clinical Trials — Wiley/PTR
• Eurycoma longifolia Improves Serum Total Testosterone in Men: A Systematic Review and Meta-Analysis — PMC
• Randomized Clinical Trial on the Use of PHYSTA Freeze-Dried Water Extract of Eurycoma longifolia — PMC
• Effect of Tongkat Ali on Stress Hormones and Psychological Mood State in Moderately Stressed Subjects — PMC
• Relationship between Alcohol Consumption and Testosterone Deficiency among Middle-Aged and Older Korean Men — PMC
• Effects of Lifestyle, Diet, and Body Composition on Free Testosterone and Cortisol Levels in Young Men — MDPI Nutrients (2025)
• Sleep Restriction and Testosterone Concentrations in Young Healthy Males: Randomized Controlled Studies — PMC
• Understanding the Secular Decline in Testosterone (full review) — PMC
• Hormone Regulation in Testicular Development and Function — PMC (Int J Mol Sci, 2024)