Description of zinc
The zinc is a trace element, that is to say that it is only found in traces in the body, the equivalent of about 2 g in all, of which 65% is concentrated in the muscles and 20% in the bones. It is present in all cells, especially in the adrenal glands, the skin, parts of the brain, the pancreas, the membranes of the eye, the prostate and sperm.
The zinc play a important role in growth, immune response, neurological and reproductive functions. It is necessary for more than a hundred vital enzymatic processes in the body (experts estimate them to be 300). It is involved in the synthesis of DNA, RNA and proteins, the immune and wound healing processes, reproduction and growth. It plays a role in mood modulation and learning, as well as vision, taste and smell. It is involved in the process of blood clotting, in the functions of the thyroid hormone, as well as in the metabolism of insulin.
- Reduce the duration and severity of colds. Research has yet to determine the most effective dosage. In treatment, the most common recommendation is to let 1 lozenge containing gluconate or some acetate zinc every 2 hours, at the first symptom. One lozenge should provide 13 mg of elemental zinc (the elemental zinc content is listed on the product label). This intensive treatment is safe if its duration does not exceed 1 week. In prevention, the most successful trials were done with a dose of 10 mg to 15 mg per day.
- Reduce the symptoms of acne. Take 30 mg of zinc daily.
|Recommended nutritional intake of zinc|
|0 to 6 months||2 mg (sufficient intake) *|
|7 to 12 months||3 mg|
|1 to 3 years||3 mg|
|from 4 to 8 years old||5 mg|
|9 to 13 years old||8 mg|
|14 to 18 years old||11 mg (boys)
9 mg (girls)
|19 and over||11 mg (men)
8 mg (women)
|Pregnant women||12 mg (18 and under)
11 mg (19 years and older)
|Nursing women||13 mg (18 and under)
12 mg (19 years and over)
Source: Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc (2002). Food and Nutrition Board, Institute of Medicine. These data are the result of a consensus between the Canadian and American authorities.
Food sources of zinc
In general, the body absorbs 15% to 40% of the zinc present in food. The oyster is the food that contains the most, but most meats and nuts contain interesting amounts. Legumes and whole grains also provide significant amounts of zinc.
|Pacific oysters, raw or steamed||100 g (3 ½ oz) (2-4 medium)||16-33 mg|
|Veal liver, stir-fried or braised||100 g (3 ½ oz)||9-12 mg|
|Beef, shoulder, flank or sirloin, braised||100 g (3 ½ oz)||7-11 mg|
|Beef or pork liver, stir-fried or braised||100 g (3 ½ oz)||6-7 mg|
|Sesame seeds, dehydrated or roasted||60 ml (1/4 cup)||3 mg|
|Sesame butter, tahini, unroasted seeds||30 ml (2 tbsp)||3 mg|
|Canned clams||100 g (3 ½ oz) (13 medium)||3 mg|
|Chicken, dark meat, boiled||100 g (3 ½ oz)||3 mg|
|Dried shiitake mushrooms||10 mushrooms (36 g)||3 mg|
|Cooked legumes||250 ml (1 cup)||2-3 mg|
|Whole roasted or dehydrated pumpkin and squash seeds||60 ml (1/4 cup)||2-3 mg|
Source: Health Canada, Canadian Nutrient File, versions 2001b and 2005 and the United States Department of Agriculture (USDA), National Nutrient Database for Standard Reference. Other dietary sources of zinc are mentioned in our Nutrient Rankings section, zinc.
The body needs very little zinc, but this contribution is essential. In our modern societies, the deficiency mild is common. In women, adolescents, children and the elderly, intake is often below the daily minimums due to eating habits deficient. Especially in pregnant women, a cold, flu or other infection can reduce the zinc content in the body, which can be harmful to the fetus. Other factors are also involved in reducing the zinc content of food, notably modern agricultural techniques, which have the effect of depleting zinc soils, and the refining of cereals.
As the best sources of zinc are foods of animal origin, vegetarians should also ensure an adequate intake of this trace element (see our table above) by consuming adequate amounts of whole grains, legumes, nuts and seeds.
|Alcoholics, diabetics, people with kidney problems or digestive absorption disorders (Crohn’s disease, for example) are at higher risk of developing zinc deficiency. People with HIV are often deficient in zinc.
Zinc deficiency (common in developing countries) can lead to a decrease in immune functions (frequent infections and wounds that heal poorly), retarded growth, impaired sense of smell and taste, decreased male fertility, dermatitis, diarrhea, depression, weight loss, irritability, listlessness.
It has long been believed that the zinc was an unimportant trace element. During the 1920s, it was discovered to be essential for the growth of farm animals. It was not until the 1960s that we realized that it also played a very important role in human health.
Cold. Despite the publication of mixed results in recent years, a systematic review published in 2011 finally concluded that zinc would decrease the duration and the gravity cold symptoms, provided it is given within 24 hours of the onset of the first symptoms. In addition, taken as preventive for at least 5 months, it would reduce the incidence of colds and the amount of antibiotics prescribed in children. The authors note, however, that it is not known what the long-term effects of such zinc intake are for a growing child. In addition, given the disparity of formulations (syrup, lozenges or tablets) and dosages used during the trials, the researchers did not reach any conclusions regarding the most effective dosage.
It should be mentioned that researchers believe that some lozenges would be ineffective due to the form of zinc that they contain or the sweetener used to mask the metallic taste of zinc. This point would explain, at least in part, the negative results obtained in part of the clinical trials. It is believed that only the gluconate and theacetate zinc would have an antiviral action, and that the dextrose, the sucrose and the mannitol would be acceptable sweeteners. On the other hand, citric and tartaric acids could inhibit the antiviral action of zinc. As for the use of glycine as a sweetener, the results are ambiguous.
Acne. Several studies conducted during the 1970s and 1980s indicated that taking supplements of zinc can reduce the number of lesions in acne patients. More recently, zinc gluconate taken for 3 months was effective in combating acne in a clinical trial without placebo on 67 subjects. In a double-blind placebo-controlled study of 332 subjects, zinc gluconate (a dose equivalent to 30 mg of elemental zinc per day) taken for 3 months reduced the number of lesions by 75% in 31% subjects. However, the oral antibiotic (minocycline in this case) was significantly more effective in reducing the number of lesions in 63.4% of the participants.
Topical application of a preparation containing an antibiotic (most often 4% erythromycin) and acetate zinc may also reduce symptoms of acne (these products are available by prescription only).
Prevention of macular degeneration. Four epidemiological studies have examined the link between dietary zinc intake and prevention of age-related macular degeneration. Two reported a positive correlation, one reported a zero association, and another reported an inverse correlation.
General immunity. The researchers observed that even a slight deficiency in zinc had a significant effect on many aspects of immune function in humans. Three double-blind placebo-controlled trials have been conducted in people 55 years of age and older. The question was whether long-term zinc supplementation (6 months to 2 years) could boost their immunity. The dosages used and the duration of treatment have varied from one study to another and the results contradict each other.
The zinc has attracted the interest of many researchers. Here are some of the fields explored.
Cardiovascular disorders. Data published in May 2004 about the AREDS study (see box below) indicates that zinc supplementation has reduced the number of deaths attributable to cardiovascular disorders. However, the zinc dosages (80 mg per day) used during this long-term test greatly exceed the maximum intake set by the American and Canadian authorities (40 mg, see the Precautions section).
Oxidative stress. Oxidative stress plays a role in aging. Two double-blind placebo-controlled clinical trials have measured the effect of zinc supplementation in healthy people over the age of 50. Taking 15 mg or 30 mg of zinc for 6 months had no effect on markers of oxidative stress (387 subjects), but a dose of 45 mg for 1 year had a positive effect on these markers (50 subjects).
|Medical or experimental uses
Macular degeneration. In a large trial (AREDS, for Age Related Eye Disease Study), taking 80 mg of zinc per day for 6 years reduced the risk of suffering from more advanced stages of this disease by 25%. The same amount of zinc, combined with 500 mg of vitamin C, 400 IU of vitamin E and 15 mg of beta-carotene gave the same results.
Note that macular degeneration requires medical diagnosis and monitoring and that this zinc dosage greatly exceeds the maximum intake set by the American and Canadian authorities (40 mg, see the Precautions section). In a more recent double-blind trial, 40 subjects took 50 mg zinc cysteinate or placebo for 6 months. In the treated group, the subjects’ visual acuity improved.
Researchers are also interested in the role of zinc in prostate cancer, the Depression, type 1 diabetes, rheumatoid arthritis and AIDS.
- The following drugs can lower the zinc level in the body:
-some vasodilator drugs (angiotensin converting enzyme inhibitors);
– oral contraceptives;
-hormone replacement therapy;
-diuretics of the thiazide class;
-chelating agents such as penicillamine or DTPA;
- Allow 2 hours between taking zinc supplements and taking the following products: antacids, antibiotics from the fluoroquinolone family and tetracyclines.
- Consult a physician before taking zinc supplements along with a potassium-sparing diuretic.
How should you use Zinc?
- To fight colds, we recommend using the gluconate and the acetate zinc and choose products sweetened with dextrose, of sucrose or mannitol. Products containing citric acid or tartaric acid, which may inhibit the antiviral action of zinc, should be avoided.
- The positive results of the AREDS study (see the Research section) have led to the marketing of various brands of antioxidant supplements aimed at preserving vision, such as ICaps®, Macuvision®, Ocuvite PreserVision®, Super Vision® and Vitalux Areds®. Their content is similar to that of the preparation used in the AREDS study, but they contain less amounts of vitamins and minerals than the original preparation.
- Zinc is marketed as salts.