Zinc an Essential Mineral
~ September 2000 No.111 ~
Although most people can list one or two vitamins that are important to have in their diet - there´s vitamin C, vitamin E and folic acid - when it comes to mineral the list is not as well known. Calcium is one of the best known mineral which we all need enough of to ensure good bone and teeth development. Iron is important to prevent anemia. But after that, there´s ... there´s zinc. Yes, zinc is a mineral that we also need in our diet even though most people don´t know why.
Zinc is found in a variety of foods, but only in very small amounts. Attaining adequate zinc nutrition can be a problem even in developed countries. In a recent report about the zinc status of the United States population, it was concluded that only about 56% of the subjects surveyed (29,103 in total) were considered to have an adequate zinc intake. Young children under 1-3 years of age, adolescent women and persons 71 years of age and older were found to be at highest risk of an inadequate zinc intake. Those with the highest zinc intakes often were consuming supplements.
Small amounts of zinc are found in every cell in the body, but larger concentrations of zinc can be found in brain, adrenal glands and the pancreas. All the zinc in our bodies probably weighs less than 2.5 grams or about the same weight as a penny. In the body zinc has an essential role in metabolism because over 60 enzymes require the presence of zinc to function. The most dramatic sign of zinc deficiency is stunted growth in infants. Adding zinc to the diet of infants and young children who suffer from low zinc intakes results in dramatic growth spurts.
Many foods contain zinc, but not in high quantities. Shell fish and red and white meats are usually considered the best sources of zinc. Most plant foods are low in zinc, but vegetarians can get their zinc from wheat germ. Zinc in breast milk is more bioavailable than zinc in cow´s milk or in most infant formulas. One difficulty preventing us from getting enough zinc is the fact that other nutrients in the body can tie up zinc and make it unavailable. Phytic acid, common in many plants, various forms of dietary fiber, polyphenols and calcium all have been shown to lower the bioavailabilty of zinc.
Even though zinc is one of the lesser known nutrients, it is still very important. Unfortunately, the recent US survey indicates that many of us are not getting enough zinc in out diets.
|Food Sources High in Zinc|
|oysters||11.25 mg / 100 g|
|T-bone steak (broiled)||4.45 mg / 100 g|
|chicken breast (roasted)||1.02 mg / 100 g|
|wheat germ||12.29 mg / 100 g|
|Source of data : USDA Agricultural Research Service, Nutrient Data Lab2|
- Briefel, R.R. et al., 2000. Zinc intake of the U.S. population: findings of the third National Health and Nutrition Examination Survey, 1888-1994. J. Nutr. 130: (5 suppl) 1367S-1373S1
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