The Vegetarian Resource Group of Tucson
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The Vegetarian Resource Group of Tucson |
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ZINC: A nutritional powerhouse By Deborah Mitchell When people are asked what benefits they can derive from the mineral zinc, many say "fighting sore throat" or "fighting a cold or flu." And they are probably right, at least according to studies that support these claims. But these studies also shed light on other benefits of zinc. One reason it's important to understand zinc is that some vegetarians may be deficient in this mineral, given that the richest sources are animal-based foods. Many plants, however, do contain at last a small amount of zinc, so even if your dietary intake of zinc is low, popping a high-potency multivitamin-mineral supplement once a day will likely take care of any shortfall. Studies reveal the value of zinc When it comes to the immune system, zinc plays a critical role: it helps maintain proper functioning of the cells that line the intestines and the blood vessels, and it may even protect against diabetes, atherosclerosis, and HIV. Let's look at some specific ways supplementing with zinc can enhance health. A recent study found that children with higher levels of zinc were less likely to be obese than children with low levels. Another recent study verified what many people have long suspected: taking zinc for the common cold significantly reduces symptoms and how long you will have them. Specifically, an over-the-counter homeopathic zinc nasal gel was given to 108 patients; another 105 patients received placebo. When the gel was given within 24 hours of symptom onset, the zinc reduced the duration of the cold from the typical 9 days to 2.3 days. Among the elderly, whose immune systems are very vulnerable to infection, dosing with zinc (15 mg daily for men, 12 mg for women) improves their resistance and their chance of surviving infection. In developing countries, where diarrhea is the biggest killer of children, those who receive zinc supplements have a 42 percent lower risk of death from persistent diarrhea than those with low zinc levels. Supplementation with zinc has recently been found to protect the integrity of the lining of blood vessels. This is especially important for prevention of atherosclerosis. Zinc can be especially helpful for people who have inflammatory bowel disease, in which lesions form. Supplementation with zinc has been shown to heal these wounds. This last remark has not been verified scientifically, but I thought it worth mentioning. Some people report that taking high doses of zinc (50 mg daily for up to 30 days) eliminates foot odor. As this is a mega dose, it should not be taken for longer than 30 days without your doctor's consent. Zinc and the immune system Why is zinc important to immune system functioning? Immune system cells called lymphocytes, which are the white blood cells that fight infections, require zinc for normal production. Researchers at the University of California Davis School of Medicine found that supplemental zinc, along with vitamin C, increase the activity of a type of lymphocytes called natural killer cells, which kill viruses and some tumor cells. The same researchers discovered that deficiencies of zinc, along with vitamins A and D, reduce the ability of natural killer cells to do their job. Other scientists, at Michigan State University in East Lansing, found that an inadequate amount of zinc can decrease the effectiveness of the immune system by up to 80% in animals. Exactly how much that benefit will translate to humans is not known, but experts believe it will be comparable. One interesting fact about zinc is that both a deficiency and an excess can inhibit normal functioning of the immune system. People who have diseases such as sickle cell anemia, kidney disease, and gastrointestinal disorders such as inflammatory bowel disease or irritable bowel syndrome often have a zinc deficiency. However, if you take mega doses of zinc for several months, you can expect your immune system to break down, making you highly susceptible to infections. (It also increases your need for copper, which needs to be supplemented as well if you are taking high doses of zinc. The general rule is to take 2 mg copper for every 30 mg zinc.) True, mega doses are sometimes given to patients in special cases, such as those with HIV. But even they receive high doses for a few weeks at most, to enhance their defense against organisms that cause candida or pneumonia. A note on zinc supplements. Some people take zinc in lozenge form to combat a cold or cough. These can cause dry mouth, nausea, and stomach upset in some people. To prevent these side effects, eat something immediately before taking the lozenges. It's also best to get lozenges that have been flavored, as "plain" lozenges taste bad. ZINC: How much do I need? Unfortunately, there are no lab tests that can clearly distinguish zinc deficiencies. According to the National Health and Nutrition Examination Survey III, only 50% of Americans consume the RDA of zinc, which is 15 mg daily for men and 12 mg daily for women. Even among nonvegetarians, the average intake of zinc from food is only 9.5-10.5 mg, leaving at least a 1.5-4.5 mg gap. Vegetarians, and especially vegans, probably have an even bigger gap to fill. If you take a high-potency multivitamin-mineral supplement daily, you may or may not be getting enough zinc to make up the difference. Check your multi to make sure you're getting enough zinc. Men need more zinc than women because there are very high concentrations of zinc in the prostate gland and in semen: in fact, semen contains 100 times more zinc than found in the blood. Sexually active men especially need more zinc. FOODS AND ZINC The richest sources of zinc are seafood, beef, poultry, legumes, peanut butter, hot and cold cereals, and dairy products. Vegetables and fruits are not good sources because the zinc in plant proteins is not as available for use by the body as is zinc from animal proteins. To help you understand how much zinc you consume and then how much you may need to supplement, here's a list of vegetarian foods and the amount of zinc they contain. Wheat germ, 1 oz.: 5.0 mg Chickpeas, 2 oz.: 2.8 Baked beans, canned, 1/2 cup: 1.8 Cashews, 1 oz: 1.6 Vegeburger: 1.6 Pecans, 1 oz: 1.6 Raisin bran, 1 oz: 1.5 Muesli, 2.25 oz: 1.3 Tahini paste, 2/3 oz: 1.1 Kidney beans, cooked 1/2 cup: 0.9 Peas, green, 1/2 cup: 0.8 Peanut butter, 2/3 oz.: 0.6 Only 20% of zinc in the diet is absorbed by the body. Dietary fiber and phytic acid, found in whole grain cereals, legumes, and nuts, inhibit the absorption of zinc. These are even more reasons to make sure your supplement is providing you with enough zinc. |
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