Because of the widespread role of zinc in several bodily functions, the symptoms of zinc deficiency can arise in several organs — muscles, skin, and bones — and organ systems — immune, digestive, reproductive, and central nervous systems.^[2] Diarrhea is a common symptom of zinc deficiency in infants, whereas poor growth and frequent infections are more common symptoms in children.^{[36][37][38][39]} Zinc deficiency can also cause a loss of appetite and alter the sense of taste and smell.^[40][38] However, these symptoms are not specific to zinc deficiency and can be caused by other conditions. Therefore, a person who suspects zinc deficiency should consult a doctor for further tests.

In 2012, the estimated global prevalence of inadequate zinc intake across all ages — the proportion of the population who have a high risk of zinc deficiency — was approximately 17%.^[39] However, the estimated prevalence varied widely among countries, reaching approximately 8% in high-income countries, and much higher in low-income and middle-income regions (e.g., approximately 26% in Sub-Saharan Africa and 30% in South Asia).^[39] Recent work published in 2020 confirmed these high prevalence estimates of zinc deficiency in low-income and middle-income countries.^[41]

Importantly, the estimated prevalence of zinc deficiency in children less than 5 years of age is also high (greater than 20%) in both high-income^[42] and low-income/middle-income countries.^[41]

ZMA is a supplement composed of zinc monomethionine aspartate, magnesium aspartate, and vitamin B6.^[43] The first study to assess the effect of supplementation with ZMA in humans was conducted by the manufacturer of this supplement and found that ZMA raised testosterone levels and increased muscle strength and power in athletes.^[44] However, follow-up studies by independent groups do not support those initial findings.^[45][46]

Animal studies show that zinc deficiency is associated with low testosterone, abnormal testicular function, and infertility.^{[47][48][49][50]} Some human studies have reported similar observations,^{[50][51][52][53]} but because of the lack of clinical trials, conclusions about the effect of zinc supplementation on sperm health or fertility aren’t currently possible.^{[54][55][53][56]}

Zinc deficiency is common in people with human immunodeficiency virus (HIV)^[57][58] and is associated with disease progression.^[59][58] Accordingly, some studies show that supplementation with zinc may delay immunological failure and reduce the occurrence of opportunistic infections in participants with both zinc deficiency and HIV.^[60][61][62]

ZMA is a proprietary blend of Zinc bound to monomethionine, Magnesium bound to aspartate, and the vitamin B6 (Pyridoxine). It is sometimes reported to give users 'weird, vivid dreams'.

This claim has not been investigated much, but a pilot study^[34] suggests that a dose of 250mg pyridoxine can alter dream perception in college aged men, through a hypothesized increased conversion of tryptophan to serotonin. This dose of B6, however, is much higher than that occurring in ZMA products; which tends to range in the 10-50mg range and usually at the lower end.

One other study has reported synergism between B6 and Magnesium in regards to anxiety reduction, when the subjects were women experiencing PMS;^[35] it is theoretically possible that the ZMA formulation enhances the actions of pyridoxine allowing the previous research's results to be relevant.

In adults, some studies show that when zinc and iron are co-ingested, zinc can reduce the intestinal absorption of iron or the incorporation of iron into red blood cells, particularly when zinc is ingested in higher amounts.^[20][63][64] In women with iron deficiency and in infants, some evidence also shows that supplementation with zinc can lower plasma ferritin (a biomarker for the body’s iron stores that is used to diagnose iron deficiency).^[65][66] Consequently, it is sometimes claimed that excess zinc intake can cause iron deficiency.

However, zinc appears to impair iron absorption only when zinc and iron are co-ingested in an aqueous solution.^[20][63][64] In contrast, when zinc and iron are mixed with food, there is no inhibitory effect of zinc on intestinal iron absorption or the incorporation of orally ingested iron into red blood cells.^{[67][20][68][69][70][71]} Additionally, the majority of human studies in adults find no effect of orally ingested zinc on plasma ferritin (body iron stores).^[20][71] Therefore, the risk of zinc-induced iron deficiency is probably negligible in most people.

It’s important to note that reduced absorption of dietary iron is not the same as iron deficiency (low iron stores as indicated by low plasma ferritin) because the body stores iron to help regulate iron absorption in line with the body’s need for iron. Also, note that iron deficiency is not the same as anemia, a condition characterized by low red blood cell count and low hemoglobin concentrations. Indeed, iron deficiency can cause anemia — specifically iron deficiency anemia — but it is not always sufficient to do so.

Testosterone is an androgen, a male sex hormone, though women need it too. In men, low testosterone has been associated with low libido^[72] and poor health outcomes, such as the development of metabolic syndrome.^[73] In men and women, low testosterone has been associated with depression.^[74][75]

Middle-aged^[76] and older^[77] men see their testosterone levels decrease by 0.4% to 1.6% per year, and many are the men who experience lower-than-average levels even in their 30s.^[78] Fortunately, quality sleep, physical activity, weight management, magnesium, zinc, and vitamin D can all help sustain healthy testosterone levels.

Lifestyle

To optimize your testosterone levels, you don’t only need the proper amounts of vitamins and minerals; you also need to sleep well, exercise, and keep a healthy weight.

1. Sleep

Lack of sleep causes numerous health issues. Notably, it decreases testosterone production^{[79][80][81][82][83]} and facilitates fat gain^[84] (and we’ll see that fat gain itself can impair testosterone production). Getting enough quality sleep is so important that we will be publishing an article on that soon.

2. Physical activity

Resistance training can raise testosterone levels for 15–30 minutes post-exercise.^[85][86] More importantly, it can benefit testosterone production in the long run by improving body composition and reducing insulin resistance.^[85]

Overtraining, however, is counterproductive. Prolonged endurance exercise especially can cause your testosterone to drop.^[87][88] Ensuring adequate recovery time will help you receive the full benefits of physical activity.

3. Weight management

Weight gain and the associated chronic diseases, such as cardiovascular disease and type 2 diabetes,^[89][90][91] are strongly linked to decreases in testosterone, particularly in middle-aged and older men.

If you gain weight (as fat), your testosterone production drops. Fortunately, if you lose weight, your testosterone production can climb back up.

Adapted from Grossmann and Matsumoto. J Clin Endocrinol Metab. 2017.^[92]

As this figure shows, observational studies have seen consistent results: in people who are overweight or obese, the greater the weight loss, the greater the testosterone increase.^[89]

These results have been echoed in clinical trials. A meta-analysis of 24 RCTs looked at weight loss caused by diet or bariatric surgery:^[93] In the diet studies, the average 9.8% weight loss was linked to a testosterone increase of 2.9 nmol/L (84 ng/dL). In the bariatric-surgery studies, the average 32% weight loss was linked to a testosterone increase of 8.7 nmol/L (251 ng/dL).

You need not lose huge amounts of weight to see a bump in testosterone levels, either: a 5% loss in weight can increase total testosterone by 2 nmol/L (58 ng/dL).^[94]

Quality sleep, physical activity, and weight management support healthy testosterone levels, and they’re synergistic: If you lack sleep, you find it harder to exercise and easier to gain fat. If you exercise, you find it easier to sleep and to keep a healthy weight. If your weight is healthy, you find it easier to exercise and easier to sleep.

If you want to know more about the lifestyle-testosterone connection, check out our infographic and article here.

Supplements

Only a few supplements have been shown to benefit testosterone production. Among those, the evidence mostly supports vitamin D and zinc, followed by magnesium. Two caveats should be kept in mind, however:

• Supplementing with a vitamin or mineral is likely to help you only if you suffer from a deficiency or an insufficiency in this vitamin or mineral.

• Correcting a deficiency or an insufficiency is more likely to raise your testosterone levels if they are low.

1. Vitamin D

Vitamin D helps regulate testosterone levels.^[95][96] Ideally, you would produce all the vitamin D you need through sunlight exposure, but if you live far from the equator, have dark skin, or simply spend most of your time inside, you may need to complement your own production with the help of foods or supplements.

Serum 25(OH)D concentrations

In Canada and the United States, the Recommended Daily Allowance (RDA) for vitamin D falls between 400 and 800 IU (International Units).^[97] These amounts, which have been criticized as too low by some,^[98][99] are attainable from only a few food sources, which is why vitamin D has become a popular supplement.

* 40 IU = 1 mcg | ** Adequate intake (AI)
Reference: Institute of Medicine. Dietary Reference Intakes for Adequacy: Calcium and Vitamin D (chapter 5 in Dietary Reference Intakes for Calcium and Vitamin D. The National Academies Press. 2011. DOI:10.17226/13050)

2. Zinc

Zinc deficiency can hinder testosterone production.^[54][100] Like magnesium, zinc is lost through sweat,^[101] so athletes and other people who sweat a lot are more likely to be deficient. Although dietary zinc is mostly found in animal products, zinc-rich foods include some grains and nuts.

* Adequate Intake (AI) Reference: Institute of Medicine. Zinc (chapter 12 in Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. The National Academies Press. 2001. DOI:10.17226/10026)

Consuming much more than your RDA^[1] can be harmful. In the short term, high doses can cause nausea^[18] and vomiting.^[102] In the long term, they can lead to a copper deficiency.^[103][104]

3. Magnesium

In males with low magnesium levels and low testosterone levels, an increase in magnesium intake can translate into an increase in testosterone production,^[105] both directly and (since one of magnesium’s functions in your body is to help convert vitamin D into its active form^[106]) indirectly.

While more common in the older population,^[107] magnesium deficiency isn’t unknown in younger people (notably athletes,^[108] since, link zinc, magnesium is lost through sweat^{[101][109][110]}). Yet getting your RDA should be easy: magnesium-rich foods are numerous and can fit all kinds of diets.

* Adequate intake (AI)
Reference: Institute of Medicine. Magnesium (chapter 6 in Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. The National Academies Press. 1997. ^[111])

If you still feel the need to supplement, keep in mind that supplemental magnesium is more likely than dietary magnesium to cause adverse effects, which is why the FDA fixed at 350 mg the Tolerable Upper Intake Level for magnesium supplementation in adults. Also, you may want to avoid magnesium oxide: it has poor bioavailability (rats absorbed only 15% in one study,^[112] and humans only 4% in another^[113]) and can cause intestinal discomfort and diarrhea.

Overhyped supplements

Numerous products are advertised as testosterone boosters, but the vast majority don’t work, though some can make you believe they do by boosting your libido. Maca, for instance, can enhance libido without affecting testosterone.^{[114][115][116][117]}

Maybe the most popular “testosterone booster” is D-aspartic acid (DAA, or D-aspartate). DAA did increase testosterone levels in two studies, one that used 2.66 g/day^[118] and the other 3.12 g/day,^[119] but two later studies found no increase with 3 g/day,^[120][121] and the latest even noted a decrease with 6 g/day.^[120]

Eat a healthy, balanced diet, so as to avoid nutritional deficiencies. If your testosterone levels are low, pay attention to your intakes of vitamin D, zinc, and magnesium. Be skeptical of supplements marketed as testosterone boosters; there’s a good chance the only thing these supplements will boost is their manufacturers’ bottom lines.

Bottom line

The interventions discussed in this article will work best for men with low testosterone, but they can also help men with normal testosterone to sustain their levels, year after year.

Supplements can help, but they can’t replace a healthy lifestyle. In order to optimize your testosterone production, make sure you get enough quality sleep on a daily basis, incorporate some resistance training into your workout program, and monitor your weight.

Try to get enough vitamin D, zinc, and magnesium through your diet. However, if dietary changes prove insufficient, supplementation can help make up the difference.

Not all testosterone deficiencies can be fixed through lifestyle or supplement interventions. It may be prudent to speak with your doctor if the options discussed above do not yield sufficient results.