Zinc in Health and Nutrition

What is Zinc?

Zinc is such a critical element in human health that even a small deficiency is a disaster. Zinc supplementation is a powerful therapeutic tool in managing a long list of illnesses. Zinc, an essential trace mineral, is required for the metabolic activity of 300 of the body's enzymes, and is considered essential for cell division and the synthesis of DNA and protein. These enzymes are involved with the metabolism of protein, carbohydrate, fat and alcohol. Zinc is also critical to tissue growth, wound healing, taste acuity, connective tissue growth and maintenance, immune system function, prostaglandin production, bone mineralization, proper thyroid function, blood clotting, cognitive functions, fetal growth and sperm production.

Zinc Deficiency

Zinc deficiency affects about 2.2 billion people around the world.(1) Mild zinc deficiency due to reduced dietary intake is common both worldwide and in the United States with an estimated 25 percent of the world's population at risk of zinc deficiency.(2)(3)(4)

Zinc deficiency has been implicated as a factor in fetal defelopment, sexual development, learning, wound healing, mental health conditions, prostate health, vision, skin and connective tissue, sexual health of men and women, weight loss and gain and many other conditions.

Zinc, Testosterone and Men's Health

Zinc is necessary to maintain normal serum testosterone. Inadequate zinc levels prevent the pituitary gland from releasing luteinizing and follicle stimulating hormones, which stimulate testosterone production. Zinc also inhibits the aromatase enzyme that converts testosterone into excess estrogen. The testosterone to estrogen ratio in men declines with aging from a high of about 50:1 to half of that, or even a low of 10:1. Higher estrogen activity results in increasd risk of heart disease, weight gain, and obesity. (5)(6)(7)

One reason for the progressive weight gain with age is that fat cells contain aromatase. More fat cells mean more estrogen which means more fat deposition.

This is further aggravated by alcohol consumption, which lowers zinc and increases estrogen, and so magnifies the problem.

In addition to the impact on hormone levels, zinc also has been proven to help the body produce healthier sperm by increasing sperm count and motility. In men with fertility issues, supplementing with zinc can improve semen quality and sperm motility, which improves the chances of conception.(8)(9)

Research studies on the effects of zinc on the prostate gland have been mixed. It seems that zinc does play a role in prostate health and that correcting low levels and deficiencies is beneficial. Zinc also plays a role in enhancing the immune system and reducing inflammation in general. These effects are also beneficial to prostate health in a general way.

Zinc Boosts the Immune System

The significance of zinc in the body's response to infection is well known (10). Zinc is essential for the normal development of neutrophils, macrophages, and natural killer cells that form the innate immune response. Zinc is also essential for the development of B-lymphocytes and T-lymphocytes which compose the adaptive immune response(11). The body also possesses an antimicrobial defense mechanism that blocks pathogens from absorbing the zinc that they require to grow and spread (12). Another mechanism attacks intracellular organisms by exposing them to toxic levels of zinc inside macrophages (13). A zinc deficiency weakens all of these defensive and protective mechanisms. As a consequence, zinc-deficient individuals experience an increased susceptibility to a variety of infectious agents (14).

Zinc is a component in thymulin (a thymic hormone) which controls and facilitates the maturation of lymphocytes. The activity of thymulin is dependent on the presence of zinc in the molecule. Serum thymulin activity becomes decreased as a result of even mild zinc deficiency and has been demonstrated to be corrected by in vivo and in vitro zinc supplementation (16).

Zinc and Type 2 Diabetes Mellitus

Laboratory studies have shown that zinc acts like insulin when administered to insulin sensitive tissue. Zinc binds to insulin receptors, activates insulin signaling pathways, and more, all of which result in glucose uptake by cells and clearance of glucose from the blood. Zinc is also necessary for the correct processing, storage, and secretion of insulin, and it can protect against beta cell loss. (37)(38)(39)

Zinc is involved in insulin synthesis and storage in secretory vesicles in the pancreas. Zinc is released with insulin when blood glucose concentrations increase (17). Zinc is also understood to stimulate glucose uptake and metabolism by insulin-sensitive tissues through triggering the intracellular insulin signaling pathway (18).

One study followed 82,297 US registered female nurses for 24 years. It measured the incidence of type 2 diabetes and their nutritional zinc intake. The data showed an 8 percent lower risk of type 2 diabetes with the highest zinc intake (median values of 11.8 mg/day) versus lowest intake of dietary zinc (median value 4.9 mg/day)(19).

The Australian Longitudinal Study on Womens Health enrolled 8,921 women for six years and measured the incidence of type 2 diabetes and dietary zinc intake. The analysis showed a 50 percent lower risk of diabetes with the highest versus lowest intake of dietary zinc (20).

The Swedish Malmo Diet and Cancer Study followed 26,132 middle-aged Swedish participants followed for 19 years. The analysis found an increased risk of diabetes with higher dietary zinc intakes yet a lower risk of diabetes in zinc supplement users versus non-users. There was also a lower risk of diabetes in those with a higher zinc-to-iron intake ratio (21).

Other studies have shown that zinc supplements improved zinc status, pancreatic beta cell function, fasting blood glucose levels, and insulin sensitivity. Shorter term studies (4 to 12 weeks) tended to not demonstrate inprovement while longer term studies (6 months or longer) did demonstrate positive results. (22)(23)(24)

A 2016 randomized, placebo-controlled trial in 55 Bangladeshi with prediabetes showed that daily supplementation with zinc sulfate (30 mg/day for 6 months) improved fasting blood glucose, as well as measures of beta cell function and insulin sensitivity (35). Similar observations were made in another recent trial in 100 Sri Lankan randomized to receive daily supplementation with zinc (20 mg of elemental zinc) or a placebo for one year. Supplemental zinc improved zinc status and measures of glycemic control (36).

Zinc Cuts Short the Common Cold

Studies have shown that zinc lozenges can reduce the duration of the common cold. For the treatment to be effective, the use of the lozenges must begin within 24 hours of the onset of cold symptoms, and continue every two to three hours while awake until symptoms resolve. Zinc, an antiviral agent and astringent, is released into the saliva, relieving cough, nasal drainage and congestion.(25)

A 2012 systematic review and meta-analysis of 13 randomized controlled trials reported that zinc supplementation in the form of lozenges or syrup shortened the duration of cold symptoms, but there was some inconsistency between studies. (26)

A 2013 Cochrane review of 14 trials involving 1,656 participants confirmed that oral zinc administrated within 24 hours of symptom onset reduced the duration of cold symptoms. The analysis also suggested that oral zinc was effective regardless of the age of participants and the type of zinc formulation (gluconate/acetate lozenges or sulfate syrup). The beneficial effects on cold duration were seen in the trials that provided more than 75 mg/day of zinc but not in trials that used lower doses. The cold symptoms cough, nasal congestion, nasal drainage and sore throat resolved the most quickly. There did not appear to be any effect on the severity of symptoms. (27)

Many supplemental zinc formulations available over-the-counter have been found to release zero zinc ions (the biologically active form of zinc) or to contain additives that either cancel out the benefit of zinc or worsen cold symptoms. It is important to do some due diligence and read the labels. (28)

Taking zinc lozenges for a cold every two to three hours while awake will result in daily zinc intakes well above the tolerable upper intake level (UL) of 40 mg/day for adults. The use of zinc at daily doses of 50 to 180 mg for one to two weeks has not resulted in serious side effects. The most common side effects reported by study participants was bad taste and nausea (27). Prolonged use of zinc at high dosages is likely to result in copper, iron and / or other deficiencies.

How Much Zinc Do You Need

Here are the daily zinc requirements. (29)

In the USA, average dietary zinc intake is about 12.3 mg/day in adults, with about 12 percent of the adult population being at risk for inadequate intake (30).

Dietary Sources of Zinc

Animal proteins are generally a good source of zinc. Animal proteins contain sulfur containing amino acids which facilitate the absorption of zinc. Plant foods also contain zinc but also contain phytates and oxalates which inhibit the absorption of zinc and other minerals. (31)

The list below provides the zinc content of selected foods in mg. of zinc.

Factors Affecting Zinc Availability

More than half of the body's zinc supply is found in muscle tissue. Zinc is also found in the bones, eyes, prostate gland, testes, skin and kidneys. Minerals may compete for absorption sites in the intestine. The absorption sites for zinc are the same ones used by iron and copper. Theefore, excess intakes of iron or copper can adversely interfere with zinc absorption. Likewise, excess intake of zinc can impair iron and copper absorption. Phytates and fiber found in unprocessed grains inhibit the bioavailability of zinc and other minerals. Exposure to toxic metals such as lead or cadmium can interfere with the absorption of zinc and displace zinc in its metabolic functions. Whole grain yeast breads enhance the absorption of zinc by producing enzymes that destroy phytates. Sprouting grains also destroys phytates. Zinc from meat products is four times more bioavailable than that found in fibrous grain foods.

Zinc is easier to absorb in smaller doses. Overall, the body absorbs 15-40% of dietary zinc, depending on the body's requirement. Zinc stored in body tissues does not function as zinc reserves, so the body depends on adequate dietary intake for its daily requirements.

Zinc is lost in also sweat and through food processing. Canning or cooking in water can deplete the amounts of zinc in food because zinc is water soluble.

Zinc Drug Interactions

The use of zinc supplements decreases the absorption of certain medications. These include including cephalexin (Keplex) and penicillamine and the antiretroviral drugs atazanavir (Reyataz) and ritonavir (Norvir). Simultaneous intake of zinc supplements with some medications like tetracycline and quinolone antibiotics may decrease the absorption of both zinc and the medications. Taking the zinc supplements and medications at least two hours apart may miimize this interaction. (32)

The therapeutic use of metal-chelating agents, such as penicillamine and diethylenetriamine pentaacetate has resulted in severe zinc deficiency. (32)

Anticonvulsant drugs, especially sodium valproate, may also precipitate zinc deficiency. Prolonged use of diuretics may increase urinary zinc excretion, resulting in increased loss of zinc. (32)

Because supplemental zinc can lower blood glucose, those taking anti-diabetic agents are advised to use zinc supplements with caution.

Zinc Toxicity

While a zinc deficiency is a health disaster, once the body's needs have been met, more is not necessarily better. If you take too much zinc, you may experience zinc toxicity, which may result in abdominal cramping, diarrhea and vomiting. Excessive zinc intake will eventually affect the balance and proper ratios to numerous other important nutrients that may include iron, calcium, selenium, nickel, phosphorus, copper, as well as Vitamin A, B1, C, and others. (34)

Single doses of 225 to 450 mg of zinc usually induce vomiting. Milder gastrointestinal distress has been reported at doses of 50 to 150 mg/day of supplemental zinc. (33)

One major consequence of long-term consumption of excessive zinc is copper deficiency. Total zinc intakes of 60 mg/day (50 mg supplemental and 10 mg dietary zinc) for up to 10 weeks have been found to result in signs of copper deficiency (34). In order to prevent copper deficiency, the US Food and Nutrition Board set the tolerable upper intake level (UL) for adults at 40 mg/day, including dietary and supplemental zinc, (34)

Recommendations on Zinc Supplements

Remember that the RDI (Recommended Daily Intake) and RDA (Recommended Daily Allowance) numbers are a statistical estimate of the amounts that prevent individuals from demonstrating deficiency signs and symptoms. The optimum nutrition level is generally higher than the RDI numbers. Unfortunately, we do not know what those numbers are. Furthermore, individual needs vary with age, sex, health status and individual genetic makeup. The simplest estimate of optimum zinc intake is assume that it is between the RDI numbers and the maximum tolerance numbers from the table above.

In general, the sum of the zinc from foods and supplements should not exceed the maximum tolerance estimates, at least for long periods of time.

Because zinc competes with iron and copper, those taking high doses of zinc supplements may develope deficiencies of these minerals. One way to avoid this is to take a good broad spectrum multi-mineral supplement. It is best to take these at different times to avoid conflict over the absorption channels.

Zinc is water soluble and is not stored effectively in body tissues. Therefore, for maximum absorption and utilization of supplemental zinc, it is best to take it in divided doses at different times of the day.

Zinc Supplements

Here are some recommended zinc products.

Zinc Caps from the Life Extension Foundation. This contains zinc monomethionine and zinc citrate.

Zinc Lozenges (Citrus-Orange Flavor) from the Life Extension Foundation. This contains zinc oxide and zinc gluconate.

Enhanced Zinc Lozenges (Peppermint) from the Life Extension Foundation. This contains zinc acetate.

Gastro-Ease(TM) from the Life Extension Foundation. This contains zinc L-carnosine and Lactobacillus reuteri.

Only Trace Elements from the Life Extension Foundation. This contains seven trace elements including zinc and copper in a balanced ratio. It does not contain iron

Copper from the Life Extension Foundation. This is a copper amino acid complex (Solaray Brand).

Iron from the Life Extension Foundation. This is Iron Protein Succinylate. This compound of iron is formulated for increased absorption and minimal gastric irritation.

Zinc Related Articles in Life Extension Magazine

How Ionic Zinc Can Stop Colds Fast, Scientifically reviewed by Dr. Gary Gonzalez, MD, in May 2022. Written by: Michael Downey.

Importance of Zinc In Maintaining Prostate Health, Scientifically reviewed by: Andrew Roberts Jr., MPH in Global Health, MS in Medical Health, in May 2022. Written by: Stephen Ramirez.

Zincs Role in Bone Health, Scientifically reviewed by: Dr. April Parks, MD, MS, in March 2021. Written by: Paz Etcheverry, PhD.

Zinc Lozenges For The Common Cold. Why Did It Take 30 Years?,Scientifically reviewed by: Dr. Shaylind Benson, ND, in May 2022. Written by: George Eby.

Zinc,Scientifically reviewed by: Dr. Gary Gonzalez, MD, in January 2021. Written by: Life Extension Editorial Staff.

How Low-Cost Zinc Helps Combat Deadly Immunosenescence,Scientifically reviewed by: Andrew Roberts Jr., MPH in Global Health, MS in Medical Health, in May 2022. Written by: Heath Ramsey.

Zinc, DHEA, Cholesterol, and Folate,Scientifically reviewed by: Dr. Gary Gonzalez, MD, in May 2022. Written by: Life Extension.

Zinc-Carnosine, Alzheimers-Diabetes, and Dihydroquercetin, Scientifically reviewed by: Dr. Gary Gonzalez, MD, in January 2021. Written by: Life Extension Editorial Staff.

Boosting Testosterone Naturally, Scientifically reviewed by: Dr. Gary Gonzalez, MD, in March 2021. Written by: Michael Aziz, MD.

Boswellia, Chlorophyllin, Zinc, and Ribogen, Scientifically reviewed by Dr. Gary Gonzalez, MD, in May 2022. Written by: Life Extension.

Reduce Risk of Stomach Ulcers and Gastritis, Scientifically reviewed by Dr. Gary Gonzalez, MD, in May 2022. Written by: Michael Downey.

Zinc References

Anti-Aging Nutrition News

Life Extension Health Protocols

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