Eating Well Boosts Your Immunity

With cold and flu season upon us, certain nutrients such as vitamin C, zinc and selenium are often touted by some to provide protection against seasonal illness. While it's true that these nutrients do boost the immune system, more is not better! "Almost all vitamins and minerals play some role in ensuring an optimal immune response," says Catherine Field, registered dietitian and spokesperson for DC, "but high doses do not help and may do harm."
Here are the 'straight goods' based on evidence provided by dietitians – your trusted source for food and nutrition advice:
Vitamin C
The Facts: Optimal vitamin C status has been identified as important for the immune cells involved in defense against viruses. The main functions of vitamin C are to help heal cuts and wounds; keep gums, teeth, and bones healthy; keep blood vessel walls strong and help absorb iron from the foods we eat. Despite being studied for over 40 years, there is insufficient evidence to advise taking more vitamin C to prevent colds or the flu. The Recommended Daily Allowance [RDA] is 75 mg for women and 90 mg for men (an additional 35 mg should be added for smokers). This is easily obtained by having 1-2 servings of vitamin C rich citrus fruits (such as oranges), or vegetables like sweet peppers and broccoli. Vitamin C is also added to a number of foods that are routinely consumed by Canadians, such as apple juice. A higher dose of vitamin C is not without side effects such as causing digestive problems.
Zinc
The Facts: Zinc is important for the cells involved in defense against viruses. Zinc is also involved in many bodily functions. It supports normal growth and development during pregnancy, childhood and adolescence. It is also required for a proper sense of smell and taste so that low zinc status can influence your appetite and enjoyment of food. The current RDA for zinc is 8 mg for women and 11 mg for men. The best sources of zinc are seafood, meat, seeds, cooked dried beans, peas and lentils. A serving of beef (75 g or 2 ½ oz) provides approximately 4.6 mg of zinc and a serving of lentils (175 mL or ¾ cup) provides almost 2 mg of zinc. Plant sources are less reliable as the level of zinc in plants depends on the content in the soil. As a result, vegetarians who mainly depend on plant sources of nutrients are advised to consult with a dietitian to insure their needs are being met.
Selenium
The Facts: Although selenium is important for a healthy immune system, there is little evidence of a deficiency in the Canadian population or evidence that consuming selenium supplements will reduce the risk of viral infections. Recommended amounts are small, only 55 micrograms daily for adults, readily obtained from nuts, seafood, organ meat, pork and whole grains. Half a cup (125 mL) of cooked brown rice provides 8-10 micrograms of selenium and a serving of mixed nuts (60 mL or ¼ cup) has about 150 micrograms of selenium.
Feed a cold and starve a fever? Not good advice!
The Facts: Viral infections, such as the flu, are often associated with a fever. However, there is no evidence that "starving a fever" by reducing the amount of food eaten will reduce a fever. In fact, a fever is a helpful means used by our own immune system in order to fight off the viral infection. If we stop eating, the immune system doesn't work as well and all of the nutrients mentioned above, as well as many others, are important to the immune system. "While it may be tempting to eat less when you're feeling unwell, try to eat smaller, more frequent meals and healthy snacks to support your body's defenses and drink plenty of water," says Field.
Source: http://www.dietitians.ca/news/media.asp?fn=view&id=14102&idstring=