Zinc

Description

Zinc is a component of many enzymes. It is involved in cell division, collagen synthesis, wound healing and using vitamin A and insulin. It is also essential for growth, immune function and the production of testosterone. Zinc plays a role in maintaining taste and smell.

Sources

Seafood, lean meat, poultry, liver, eggs, nuts, milk, cheese and legumes are good sources of zinc. Although whole grain cereals contain zinc, it is not well absorbed.

Approximate Zinc Content
 Food  Portion  Content
 Alaska king crab 85 g 6.5 mg
 Beef liver 85 g 4.5 mg
 Beef, sirloin 85 g 4.6 mg
 Chickpeas 250 mL 2.5 mg
 Egg 1 0.6 mg
 Milk 250 mL 1.0 mg
 Food  Portion  Content
 Oysters, raw 6 76.3 mg
 Pecans 20 halves 1.3 mg
 Pine nuts 28 g 1.8 mg
 Turkey 84 g 3.8 mg
 Whole wheat bread 250 mL 3.5 mg

Oysters are very rich in zinc. Because zinc is required for the production of testosterone, aphrodisiac properties have been attributed to oysters. In reality however, they have no effect whatsoever on libido or sex drive.

Recommended Daily Allowance (RDA)

Recommended average daily nutrient intake that is sufficient to meet the nutrient requirements of nearly all (97 to 98%) healthy individuals in each age and gender group. The RDA should only be used as a guide for daily individual intake.

Zinc Requirements
 Age  Men   Women 
 1-3 years 3 mg 3 mg
 4-8 years 5 mg 5 mg
 9-13 years 8 mg 8 mg
 14-18 years 11 mg 9 mg
 Age  Men   Women 
 19-50 years 11 mg 8 mg
 > 50 years 11 mg 8 mg
 Pregnancy   +3 mg
 Breastfeeding   +4 mg

The average Canadian diet consists of 10 to 15 mg of zinc per day.

Deficiency

Severe deficiencies are most often seen in developing countries. However, mild deficiencies can occur in persons who suffer from malnourishment and in strict vegetarians. Zinc deficiency is difficult to diagnose and is believed to be relatively common in children, in those following special diets and in the elderly.

Zinc deficiency is characterized by hair loss, reduced appetite, apathy, depression, diarrhea, frequent infections, rash, dermal ulcers, delayed wound healing, loss of taste and smell, light sensitivity and night blindness, delayed growth and acne. Zinc-deficient women who are pregnant can give birth to low birth weight babies.

Toxicity

Zinc toxicity is rare unless one is taking supplements or eating oysters on a regular basis. Signs and symptoms of zinc toxicity include agitation, a lowering of good cholesterol and an increase of bad cholesterol, dehydration, diarrhea, epigastric pain, hypotension, nausea and vomiting.

Supplements

The amount of zinc in supplements is based on the type of salt that is used.

Number of mg to obtain 1 mg of elemental zinc
 Zinc chloride 2.1 mg
 Zinc gluconate 7.5 mg
 Zinc sulfate 4.4 mg

The vast majority of people do not need zinc supplements. Furthermore, prolonged use of high doses can reduce copper absorption. This property is used to treat Wilson’s disease which is caused by an accumulation of copper in the liver. Doses of 22.5 to 34 mg, 3 times a day, are administered.

Zinc supplements may be administered if one is diagnosed with a deficiency. For example, a daily 5 mg dose can stimulate growth in children experiencing a failure to thrive as a result of a zinc deficiency.

Supplements should be taken on an empty stomach since food reduces its absorption. In fact, it is preferable to take several smaller doses throughout the day rather than one large dose.

Zinc is used for several health problems but many of the claims that have been made on its effectiveness to prevent prostate problems, prevent or accelerate treatment of the common cold and prevent eye diseases, remain unsubstantiated. Zinc sulfate is not effective for reducing the frequency of loss of taste experienced by those undergoing head or neck radiation.

Persons with kidney stones should avoid taking zinc supplements since they can worsen the illness. Medical monitoring is essential for prolonged use.

Watch what you eat. Nutrition has a significant impact on health!