Zinc After 40

After the age of forty, interest in zinc grows: it is associated with immunity, men’s health, and recovery after training. The editorial team looked into what actually changes with age in the metabolism of this trace element, who may benefit from a supplement, and where the line between support and excess lies.

Why age changes zinc metabolism

Zinc is a trace element involved in the work of more than three hundred enzymes and thousands of regulatory proteins. In an adult’s body there are only about two to three grams of it, and the vast majority is concentrated in the muscles and bones. There is no special “depot” from which the body could quickly draw zinc in case of a shortage, so the status of the trace element depends on daily intake from food.

After the age of forty, several factors gradually change at once in most people. The overall caloric content of the diet decreases, diets restricting red meat appear more often, and appetite worsens during stress or illness. A smaller volume of food automatically means fewer trace elements, even if the quality of nutrition has not changed.

In parallel, absorption also changes. With age, stomach acidity decreases, and some people regularly take proton pump inhibitors, diuretics, or other drugs that affect mineral metabolism. Researchers of immune aging note that a suboptimal zinc status occurs noticeably more often in older people than in the young (Haase, Rink, 2009).

It is important to understand: age in itself is not an indication for taking a supplement. A forty-year-old person with a varied diet that includes meat, fish, eggs, legumes, and whole-grain products usually gets enough zinc. The question of supplements arises when the risk factors discussed below appear.

Zinc, immunity, and “inflammaging”

One of the best-studied functions of zinc is support of the immune system. It is needed for the maturation of T-lymphocytes in the thymus, for the work of natural killers, and for the regulation of inflammatory cytokines. The thymus naturally shrinks with age, and a zinc deficiency can accelerate this process.

Scientists describe a phenomenon called “inflammaging” — the chronic low-intensity inflammation characteristic of aging. Zinc acts as one of the regulators of the NF-κB signaling pathway, and when it is lacking, the inflammatory response can become excessive. This is precisely why zinc status is regarded as one of the modifiable factors of immune aging.

In a randomized study involving elderly people, taking zinc for a year was accompanied by a lower frequency of infections and a reduction in markers of oxidative stress compared with placebo (Prasad et al., 2007). It is worth noting that the participants were older than 55, so transferring the results to forty-year-old athletes should be done with caution.

The common cold is worth mentioning separately. Meta-analyses show that zinc lozenges, started within the first day of symptoms, can shorten the duration of a cold in adults (Science et al., 2012). This is a short course of a therapeutic nature, not daily prevention, and it does not apply to ordinary capsules that are swallowed whole.

Hormones, muscles, and recovery

For men over forty, the topic of zinc often comes up in connection with testosterone. The connection really does exist: in a classic study, an artificially induced zinc deficiency in young men lowered testosterone levels, while in elderly people with a marginal deficiency a supplement raised it (Prasad et al., 1996).

However, the key word here is deficiency. If there is enough zinc in the diet, additional intake does not raise testosterone above the norm. In the study by Koehler et al., a high dose of zinc in healthy men did not change the level of serum testosterone. In other words, the supplement can only “release the brake”, if there is one, but not press the gas.

For people who train, zinc is also important with regard to tissue recovery, protein synthesis, and the healing of microtraumas. Intense training increases the loss of the trace element through sweat and urine, and the review by Micheletti et al. (2001) notes that athletes with a restricted diet more often have a reduced zinc status.

For women over forty who are entering perimenopause, zinc is not a means of “hormonal correction”. Its role here is general support of metabolism, the condition of the skin, hair, and nails, and immunity. Any hormonal questions of this period are resolved with a gynecologist-endocrinologist.

Who is at risk and how much is needed

At the greatest risk of getting insufficient zinc are those who eat mainly plant-based food, follow long low-calorie diets, abuse alcohol, have intestinal diseases, or constantly take drugs that affect mineral absorption. Plant products contain phytates, which bind zinc and reduce its absorption.

• vegetarians and vegans — the requirement may be higher because of phytates;
• people on a prolonged calorie-deficit diet;
• patients with Crohn’s disease, celiac disease, after bariatric surgery;
• people who regularly consume alcohol;
• those who take diuretics or proton pump inhibitors for a long time.

Intake norms do not increase with age: for adult men the American RDA is 11 mg per day, for women — 8 mg. The European body EFSA calculates the requirement depending on the phytate content of the diet, so its values are broader. The tolerable upper intake level for adults is 25 mg per day according to EFSA and 40 mg according to American norms.

Practical conclusion: for most adults a reasonable choice is a supplement that covers approximately the recommended norm, that is, 10–15 mg of elemental zinc, and only in the presence of risk factors. Higher doses are appropriate only as short courses on a doctor’s recommendation, for example after a laboratory-confirmed deficiency.

Risks of excess and interactions

After the age of forty, many people simultaneously take several complexes: multivitamins, “men’s” formulas, ZMA, immune-support products. Each of them may contain zinc, and the total dose imperceptibly exceeds 40–50 mg per day. This is most often how chronic excess arises.

The main risk of prolonged intake of high doses is a secondary copper deficiency. In the intestine, zinc stimulates the synthesis of metallothionein, which binds copper and prevents it from being absorbed. Cases of anemia, neutropenia, and neurological disorders due to copper deficiency caused by prolonged zinc excess have been described (Willis et al., 2005).

Short-term excess manifests as nausea, vomiting, abdominal pain, and a metallic taste. Chronic excess is more insidious: a person may feel no symptoms for years, until changes appear in a blood test. The review by Plum et al. (2010) not without reason calls zinc “an essential toxin”.

The AREDS study is worth mentioning separately: high doses of zinc (80 mg) together with antioxidants and copper were studied as a means of slowing the progression of age-related macular degeneration (AREDS, 2001). This is a therapeutic regimen for a specific eye disease under the supervision of an ophthalmologist, not an example for self-directed prevention.

Editorial Conclusions

After the age of forty, the requirement for zinc does not formally increase, but the likelihood grows that less of it will come from food and that it will be absorbed worse. Therefore it is sensible to assess your diet and risk factors rather than take a supplement “just in case”.

Zinc is important for immunity, recovery, and the normal work of the hormonal system, but it raises testosterone only in the presence of a deficiency. One should not expect a rejuvenating or anabolic effect from it.

If a supplement is needed, it is sensible to choose a dose within the recommended norm, take it with food, and count zinc in all the complexes you consume. Prolonged intake above the tolerable upper level threatens copper deficiency.

The editorial team also recommends reading our materials “Magnesium After 40”, “How to Choose Quality Zinc: What to Look for on the Label”, and “Zinc and Sleep” — they complement this topic from other perspectives.

References

1. Institute of Medicine (US) Panel on Micronutrients. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington (DC): National Academies Press; 2001.
2. Haase H, Rink L. The immune system and the impact of zinc during aging. Immun Ageing. 2009;6:9.
3. Prasad AS, Beck FW, Bao B, et al. Zinc supplementation decreases incidence of infections in the elderly: effect of zinc on generation of cytokines and oxidative stress. Am J Clin Nutr. 2007;85(3):837–844.
4. Prasad AS, Mantzoros CS, Beck FW, Hess JW, Brewer GJ. Zinc status and serum testosterone levels of healthy adults. Nutrition. 1996;12(5):344–348.
5. Koehler K, Parr MK, Geyer H, Mester J, Schänzer W. Serum testosterone and urinary excretion of steroid hormone metabolites after administration of a high-dose zinc supplement. Eur J Clin Nutr. 2009;63(1):65–70.
6. Science M, Johnstone J, Roth DE, Guyatt G, Loeb M. Zinc for the treatment of the common cold: a systematic review and meta-analysis of randomized controlled trials. CMAJ. 2012;184(10):E551–E561.
7. Willis MS, Monaghan SA, Miller ML, et al. Zinc-induced copper deficiency: a report of three cases initially recognized on bone marrow examination. Am J Clin Pathol. 2005;123(1):125–131.
8. Age-Related Eye Disease Study Research Group. A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E, beta carotene, and zinc for age-related macular degeneration and vision loss: AREDS report no. 8. Arch Ophthalmol. 2001;119(10):1417–1436.