Zinc

Zinc is a trace element (micronutrient or small molecule) essential to the proper functioning of the body’s reproductive system, nervous system, and immune response. Zinc is concentrated largely in muscles and bones, but is also found in skin cells, the adrenal glands, the pancreas, the prostate, sperm cells, and certain parts of the brain and the eye membrane. 

Roles

Zinc is vital to growth and development. 

What does zinc do? 

Zinc is necessary for: 

• The breakdown of carbohydrates, fats, and proteins;
• Cell division and development (fetus);
• The growth and development of children and teens;
• The production of DNA and RNA (gene expression);
• The functioning of the immune system (to fight infection);
• The healing process;
• The metabolism of insulin;
• The functions of the thyroid hormone;
• Sexual maturation;
• Fertility;
• Reproduction;
• Maintaining your sense of smell, taste, and vision.

Needs

Recommended Dietary Allowances for Zinc (mg/day): 

 Source: www.passeportsante.net; Food and Nutrition Board, Institute of Medicine, Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc, 2002. This data reflects a consensus between Canadian and U.S. health authorities.

Lacking sufficient scientific evidence, authorities have established adequate intake (AI) amounts rather than recommended dietary allowances (RDAs) for this age group. Adequate zinc intake is based on observed average intakes in North American babies in good health.

Sources

The body absorbs 15% to 40% of the zinc present in food. Foods rich in zinc include red meat, certain seafood such as oysters, whole grain products, nuts, legumes, and certain enriched cereals. 

Food Sources for zinc: 

Source: www.passeportsante.net; Health Canada, Canadian Nutrient File, versions 2001b and 2005 and U.S. Department of Agriculture (USDA), National Nutrient Database for Standard Reference.

Deficiency

A slight zinc deficiency is common. Your zinc intake may be insufficient either because you don’t consume enough zinc or your body cannot manage to properly absorb it in the intestine. Deficiency occurs most often among: 

• Women;
• Pregnant women with a cold or the flu;
• Children and teens;
• Seniors;
• Individuals on a protein-restricted diet (e.g., vegetarians);
• Alcoholics;
• HIV carriers;
• Diabetics;
• Individuals suffering from intestinal, liver, or kidney disease;
• Individuals with intestinal absorption problems.

Signs of zinc deficiency: 

• Decreased immune function, which results in poor wound healing and frequent infection;
• Growth retardation;
• Problems with sense of smell or taste;
• Nocturnal vision problems;
• Skin problems;
• Loss of appetite;
• Weight loss;
• Depression;
• Irritability;
• Hair loss;
• Diarrhea;
• Delayed puberty and sexual maturation

Indications

A zinc supplement may be effective in: 

• Reducing symptoms related to acne;
• Reducing the symptoms and duration of a cold;
• Preventing macular degeneration (irreversible eye disease leading to vision loss);
• Stimulating the immune system in people age 50 and over (for a period of 6 months to 2 years).

Individuals who could benefit from a zinc supplement: 

• Vegetarians;
• Children and teens who exhibit growth retardation;
• Alcoholics;
• Individuals suffering from intestinal malabsorption disease or chronic diarrhea.
• The supplement dose should not exceed 40 mg for adults and 34 mg for pregnant women.***

Adverse effects

Zinc supplements do not exhibit any significant toxicity in the generally recommended doses. They may, however, produce side effects if taken for an extended period of time. 

Signs of excess zinc: 

• Copper deficiency and depletion of iron (more than 100 mg of zinc per day);
• Diarrhea (more than 100 mg of zinc per day);
• Intestinal irritation (more than 100 mg of zinc per day);
• Kidney problems (more than 100 mg of zinc per day);
• Decreased immune response (more than 300 mg of zinc per day);
• Decreased efficiency of transporters (HDL) that help remove cholesterol from blood vessel walls.

Cons-indications

• Long term excess may be toxic;
• Chronic use of 450 mg to 1,600 mg per day may cause anemia;
• Individuals suffering from Menkes syndrome (defective enzyme that aids in intracellular copper transport), as a high zinc intake further reduces copper absorption;
• Allergy or hypersensitivity to zinc.

Interactions

Natural health products or vitamin supplements: 

• Iron, calcium, and phosphorous may decrease zinc absorption;
• Phytates (composed of phosphorous, which binds to metals and prevents them from being absorbed in the intestine) or fiber decrease zinc absorption;
• Protein (plant or animal) affects zinc absorption;
• Zinc may decrease iron, copper, and folate absorption.

Medication that may lead to zinc deficiency: 

• Anticonvulsants;
• Vasodilator medication;
• Hormone replacement therapy;
• Oral contraceptives;
• Antacids*;
• Thiazide diuretics;
• Chelating agents (bind to metals to form a soluble complex).

Zinc may decrease the absorption of certain antibiotics in the fluoroquinolone and tetracycline group*.

Additional information

*Take every two hours. 

***If you plan to take a zinc supplement, ask your pharmacist to help you choose the solution that’s best for you based on your health and any drugs you take. 

Other names

Zn, Zinc acetate, Zinc citrate, Zinc gluconate, Zinc lactate, Zinc oxide, Zinc sulfate