Does Zinc Increase Testosterone? Only If You Are Deficient, and Here Is How to Know

Zinc is in every testosterone supplement sold, and the claim is always the same: zinc boosts testosterone. The claim traces back to one study, and that study showed something narrower and more useful than the headline.

Here is what it showed, what later research added, who is actually likely to be low, and how to take zinc without creating the deficiency it is often paired with.

The study everyone quotes

In 1996, Prasad and colleagues published two small experiments. In the first, four healthy young men were put on a zinc-restricted diet for twenty weeks. Their testosterone fell by nearly three quarters. In the second, nine elderly men with marginal zinc deficiency took zinc for six months. Their testosterone roughly doubled, from about 8 to 16 nmol/L.

Thirteen men, all of them deficient by design or by selection. The finding is real: zinc deficiency lowers testosterone and correcting it restores what was lost. The finding is also the whole story. Nothing in the study suggests zinc raises testosterone in men who already have enough.

What happens in men who are not deficient

The trials that followed tested exactly that.

• Koehler and colleagues, 2009. Trained men with normal zinc status took 30 mg of zinc daily for eight weeks. Testosterone did not change.
• Wilborn and colleagues, 2004. The ZMA formula, zinc with magnesium and B6, was tested in resistance-trained men for eight weeks. No change in testosterone, muscle or strength, in a study that found the earlier positive ZMA result came from a trial funded by the product's maker.
• Later work in athletes has occasionally shown zinc blunting the drop in testosterone after exhausting exercise, which is a recovery effect in people losing zinc through sweat rather than a boosting effect.

Reading it by zinc status:

• Deficient — supplementing restores testosterone toward normal, sometimes substantially
• Marginal, with heavy training or sweating — may prevent a training-related dip
• Replete — no effect

The serum testosterone PK model is worth a look for anyone who thinks a mineral will do what exogenous testosterone does. The scale of the two effects is not close.

Why zinc still matters

Zinc is a cofactor for several hundred enzymes. It is needed for immune function, wound healing, taste and smell, sperm production and DNA synthesis. A deficiency costs performance and recovery through all of those routes, and testosterone is only one of them.

So the question is not whether zinc boosts testosterone. It is whether you are low, and a meaningful number of people in India are.

Who is likely to be low

• Vegetarians. Zinc from plant foods is poorly absorbed because phytates in grains, legumes and seeds bind it. A vegetarian may need 50 percent more zinc than an omnivore to absorb the same amount.
• Heavy sweaters. Zinc is lost in sweat, and long training in Indian heat adds up.
• People in a long deficit. Less food, less zinc.
• Regular alcohol drinkers. Alcohol increases zinc loss through the kidneys.
• Anyone with gut conditions that reduce absorption.
• Older men, in whom absorption declines.

Indian dietary surveys consistently find zinc intakes below the ICMR recommendation of 17 mg a day for men, with cereal-based diets the main reason.

The symptoms

Vague, and easily blamed on something else: frequent colds, slow wound healing, reduced sense of taste, hair thinning, low libido, poor appetite and, in athletes, slower recovery. None of them is specific. All of them together in a vegetarian who trains hard is a reason to test.

Testing

Serum zinc is the standard test and it is imperfect. Zinc in the blood falls with inflammation, infection and a recent meal, and the blood holds a tiny fraction of the body's total. A fasting morning serum zinc below about 70 mcg/dL is suggestive. A normal result does not fully rule deficiency out.

Because of that, a reasonable approach when symptoms fit is a supervised trial: test, supplement for eight weeks, retest, and note whether the symptoms changed. The blood test selector adds serum zinc alongside ferritin, B12 and vitamin D when the reason for testing is fatigue or poor recovery, since those four deficiencies overlap heavily in this population and are best read together in the bloodwork analyzer.

Dose and form

• Zinc bisglycinate — high absorption, well tolerated, the best default
• Zinc picolinate — high absorption, well tolerated
• Zinc citrate — good absorption, cheap and effective
• Zinc gluconate — moderate absorption, common in lozenges
• Zinc oxide — poor absorption, the form in cheap multivitamins, largely wasted

The upper limit for long-term intake is 40 mg of elemental zinc a day. For correcting a likely deficiency, 15 to 30 mg elemental daily for eight to twelve weeks is the usual range, then a lower maintenance dose or diet alone.

Read the label for elemental zinc, not total compound weight: 50 mg of zinc gluconate is about 7 mg of zinc. Take it with food to avoid nausea, and away from iron and calcium supplements, which compete for absorption.

The copper problem

This is the part the testosterone supplement labels leave out. Zinc and copper compete for absorption, and sustained zinc intake above 40 to 50 mg a day drives copper deficiency. That causes anaemia, low white cell counts and, over longer periods, nerve damage.

Anyone taking more than 30 mg of zinc daily for months should take 1 to 2 mg of copper alongside it, and anyone on a high-zinc stack with unexplained fatigue should have copper checked. This is also the reason a zinc supplement is for a defined correction period with bloodwork, not something to run indefinitely alongside other zinc sources in a stack.

The short version

Zinc restores testosterone in men who are deficient and does nothing in men who are not. Vegetarians, heavy sweaters, drinkers and dieters are the ones likely to be low. Test in the morning fasted, supplement 15 to 30 mg of bisglycinate or picolinate with food for eight to twelve weeks, retest, and add copper if the dose stays high.

Related tools

• Blood test selector: adds serum zinc with the other deficiencies that overlap with it
• Bloodwork analyzer: reads zinc alongside ferritin, B12 and vitamin D
• Serum testosterone PK model: puts a mineral's effect in proportion

Frequently asked questions

Does zinc increase testosterone?

Only in men who are zinc deficient, where it restores testosterone toward normal. In men with adequate zinc, trials at 30 mg daily found no change.

How much zinc should I take for testosterone?

If deficient, 15 to 30 mg of elemental zinc daily for eight to twelve weeks, then retest. If not deficient, supplementing will not raise testosterone. Do not exceed 40 mg a day long term.

What is the best form of zinc?

Zinc bisglycinate and zinc picolinate absorb well and are gentle on the stomach. Zinc oxide, common in cheap multivitamins, is poorly absorbed.

What are the symptoms of zinc deficiency?

Frequent colds, slow wound healing, reduced taste, hair thinning, low libido, poor appetite and slower recovery from training. None is specific, so testing is worthwhile when several appear together.

Can too much zinc be harmful?

Yes. Sustained intake above 40 to 50 mg a day causes copper deficiency, which leads to anaemia, low white cells and nerve problems. Take 1 to 2 mg of copper alongside any long-term zinc dose above 30 mg.

Are vegetarians more likely to be zinc deficient?

Yes. Phytates in grains, legumes and seeds bind zinc and reduce absorption, so vegetarians may need around 50 percent more zinc than omnivores to absorb the same amount.

This article is educational and is not medical advice. See the medical disclaimer.