The most powerful protection that you can give your immune system is to eat a well-balanced diet containing a variety of fruits, vegetables, whole grains, seeds and nuts, and seafood, says Dr. DiMilia. These foods are high in nutrients that can help keep your immune system healthy. What's more, some of these nutrients are antioxidants, which may help give the immune system an added boost.
Here's why antioxidants are so important. Every second, immune cells in your body are hit by a barrage of free radicals, harmful oxygen molecules that are created in enormous numbers every day. Since free radicals are missing an electron, they rush through your body, stealing electrons wherever they can find them. And every time they grab an electron, another cell is damaged.
The antioxidants in such foods as brightly colored fruits and vegetables, however, literally come between free radicals and healthy immune cells, offering up their own electrons. This neutralizes the free radicals, stopping them from doing further harm. In the process, your body's immune cells stay protected and strong.
"When your immune system is going to fight something, it fights it by oxidizing it,” says Shawn Talbott, PhD, a nutritional biochemist and author of The Health Professional’s Guide to Dietary Supplements. "So your immune system will actually give a virus or bacteria a blast of oxidation to try to kill it. Therefore, if you are fighting off a lot of these viruses or bacteria, you will have a lot of oxidation happening in your body and will need more antioxidants," he says.
In a study at Memorial University of Newfoundland in Canada, researchers found that people who got the most of a variety of nutrients, including antioxidants such as beta-carotene and vitamins C and E, in their diets were able to produce greater numbers of natural killer cells - immune cells that search out and destroy bacteria and other invaders - than folks getting the least. Another study found that people who got large amounts of a variety of antioxidants typically got sick about 23 days a year, while those getting smaller amounts got sick about 48 days a year.
Even though vitamin C is a powerful antioxidant, it helps the immune system in yet another way. The body uses vitamin C to make interferon, a protein that helps destroy viruses in the body. Plus, vitamin C may increase levels of a compound called glutathione, which has also been shown to keep the immune system strong.
In one large study, researchers at the University of Helsinki in Finland reviewed 21 smaller studies that looked at how well vitamin C was able to beat colds.""They found that people getting 1,000 milligrams of vitamin C a day were able to shorten the duration of their illnesses and reduce their symptoms by 23 percent.
And a more recent Swiss review of numerous studies revealed that 1 gram of vitamin C was effective in shortening the duration of respiratory infections including the common cold.
The Daily Value (DV) for vitamin C is 60 milligrams, but many researchers say that 200 milligrams is probably the minimum amount you need to maximize immunity. It's easy to get this much vitamin C in your diet, Dr. Block adds. Half a cantaloupe, for example, has 113 milligrams of vitamin C, almost twice the DV, while a half-cup of Brussels sprouts has 48 milligrams, or 80 percent of the DV. Of course, yOU can also get a lot of vitamin C in citrus fruits, broccoli, guava, strawberries, rutabagas, radishes, and rose hips tea.
Vitamin E has also gotten a lot of attention for its role in boosting immunity. The body uses vitamin E to produce a powerful immune protein called interleukin-2, which has been shown to tackle everything from bacteria and viruses to cancer cells. The DV for vitamin E is 30 lU, and good sources include dark green leafy vegetables, walnuts and pecans, wheat germ, peanut butter, and vegetable oils. (‘The Doctor’s Book of Food Remedies’, by Selene Yeager and the Editors of ‘Prevention’ magazine)