Testosterone

Testosterone is a hormone produced primarily in the testes in men, and the ovaries in women, and is relevant to sexual developement, muscle building, fat loss, some aspects of cognition, and hair loss.

Testosterone levels may not tell the whole story of how testosterone is functioning in the body. Your total testosterone can be divided into three categories:

• Tightly bound testosterone. About two-thirds of the testosterone in your blood is bound to sex hormone binding globulin (SHBG). Your body can’t use it.

• Loosely bound testosterone. About one-third of the testosterone in your blood is bound to albumin. Your body can use it, but with some effort.

• Free testosterone. A small percentage of the testosterone in your blood (1–4%, as a rule) just floats around freely. Your body can readily use it, and the enzyme 5-alpha-reductase can convert it to dihydrotestosterone (DHT), a very potent androgen.

Together, your loosely-bound and free testosterone compose your bioavailable testosterone, which has a greater impact on your health than your total testosterone.

Testosterone boosters are supplements that increase your production of testosterone. Supplements that increase only your percentage of free testosterone or DHT are often included in this category.

Supplements that inhibit CYP19A1, the aromatase enzyme, are indirect testosterone boosters in men. CYP19A1 serves many purposes, one of which is to convert testosterone to estradiol, the predominant form of estrogen. Inhibiting this enzyme reduces the percentage of testosterone that gets converted to estradiol.

Contrary to what you might think, the male body needs estradiol,^[1] though in lesser quantity than women need. When the body detects that estradiol levels are too low, it reacts by increasing its production of the base material it needs to make estradiol: testosterone.

Aromatase inhibitors can boost testosterone on their own, but they can also complement other testosterone boosters. If you take a supplement that increases testosterone without inhibiting the aromatase enzyme (through hypothalamic stimulation, for instance), you may find yourself with more estradiol than you need, a situation that taking an aromatase inhibitor may remedy — if you’re a man, that is. As we saw, aromatase inhibitors hinder the conversion of androgens to estrogens; in premenopausal women, however, ovaries produce most of the estrogen, so aromatase inhibitors are much less effective.

If you are looking for an actual stack of supplements to take, we recommend you look at our increasing testosterone stack.

The Human Effect Matrix looks at human studies (it excludes animal and in vitro studies) to tell you what supplements affect testosterone.

Grade	Level of Evidence [show legend]
	Robust research conducted with repeated double-blind clinical trials
	Multiple studies where at least two are double-blind and placebo controlled
	Single double-blind study or multiple cohort studies
	Uncontrolled or observational studies only

Level of Evidence ? The amount of high quality evidence. The more evidence, the more we can trust the results.	Supplement	Magnitude of effect ? The direction and size of the supplement's impact on each outcome. Some supplements can have an increasing effect, others have a decreasing effect, and others have no effect.	Consistency of research results ? Scientific research does not always agree. HIGH or VERY HIGH means that most of the scientific research agrees.	Notes
	Dehydroepiandrosterone	Notable	High See all 18 studies	There appears to be an increase in testosterone following DHEA supplementation, but the vast majority of literature is in menopausal women (where testosterone contributes to libido). There is variability in the results, and DHEA is unreliable in increasing testosterone, but this unreliability extends to all demographics and subjects (with limited evidence of DHEA increasing testosterone in all studies including youthful athletes, which are less studied).
	Alcohol	Minor	- See all 9 studies	There appears to be a time-dependent influence on testosterone, with acute doses of alcohol increasing testosterone secondary to creating energy influx in the liver (small enough of an increase to be 'somewhat' effective but may contribute to libido) whereas abuse is known to reduce testosterone levels more notably. The acute increase in testosterone is thought to be related to spikes in libido
	Ashwagandha	Minor	Very High See all 7 studies	Testosterone may be increased in infertile men (who have a reduction in testosterone) and men undergoing strength training, but there is currently no evidence to suggest an inherent testosterone boosting effect in otherwise normal men.
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• Aspartic acid on trial: no, it doesn’t boost testosterone

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