How Nutrition Boosts Immunity
An intricate network of proteins, cells, tissues, systems, and organs (like the skin, respiratory, and digestive tracts—our first line of defense) are designed to protect us from antigens, a collective term for bacteria, viruses, allergens, and other organisms that make us sick.
If disease agents get past the first line, they go up against a team of white blood cells, known as leukocytes, lymphocytes, B-cells, T-cells, Killer T-cells, macrophages, and more. Every white blood cell begins its life in bone marrow as a stem cell. For these cells to do their job effectively, we need to exercise, eat a balanced diet, and avoid foods high in saturated and trans fats.
Vitamins A and C
Vitamins A and C help lymphocytes reproduce properly when the body is exposed to a virus, and they enable neutrophils and macrophages to surround and kill invasive bacteria. Vitamin A is also important for strong and healthy skin. Vitamin C, which produces the protein interferon, boosts the cells that seek and destroy disease agents once they’re present in the body.
Sources of vitamin A and C include colorful vegetables, fruits, whole grains, beans, and foods rich in red, orange, and/or yellow beta-carotene, like sweet potatoes, carrots, squash, cantaloupe, and pumpkin. A 2009 study published in the Journal of Agricultural and Food Chemistry showed that the skin on pumpkins could reduce the incidence of microbes that cause millions of cases of yeast infection in children and adults.
Vitamin E helps the immune system by producing interleukin-2, a protein that kills bacteria, viruses, and possibly cancer cells. Interleukin-2 appears in the body as a reaction to being invaded by germs. Sources include wheat germ oil, almonds, peanut butter, spinach, broccoli, kiwi, and mango.
Researchers at Harvard found that people who drank five cups of black tea a day for two weeks produced extra-strength T-cells, which help resist cold and flu viruses. Green tea is believed to be just as effective. The interferon, or proteins, found in tea may also help protect against food poisoning, infected cuts, athletes’ foot, tuberculosis, and malaria.
Not getting enough zinc in your diet, particularly among vegetarians and people who’ve reduced their intake of beef, hurts immunity. A lack of zinc, which helps with the development of white bloods, can raise the risk of infections, fevers, coughs, and mucus build up. Just three ounces of lean beef provides about 30 percent of our daily zinc requirement. Other sources include oysters, fortified cereals, pork, poultry, yogurt, and milk.
The healing benefits of chicken soup aren’t just an old wives’ tale. Researchers at the University of Nebraska found that chicken soup, specifically an amino acid called cysteine found in it, blocked the movement of inflammatory cells. The salty broth mimics the action of cough medicines by keeping mucus thin, while garlic and onions are believed to increase the body’s immune-boosting ability.
Selenium, found in oysters, lobsters, crabs, and clams, increases the production of proteins called cytokines, according to a small study conducted in Great Britain. Cytokines may help the body fight off viruses that cause influenza. The omega-3 fats found in many seafoods, particularly salmon, have also been shown to increase the concentration of T-cells and cytokines.
Probiotics are live, healthy cultures found in yogurt that keep the intestinal tract free of germs that cause diseases. An Austrian study found that seven ounces of yogurt a day was enough to do the job, while a Swedish investigation found that daily supplements of Lactobacillus reuteri, a probiotic that stimulates white blood cells, resulted in 33 percent fewer sick days among workers when compared to a placebo. When buying yogurt, choose one with less than 200 calories, 4 g of fat, and 30 g of sugar per serving.
There is limited evidence that garlic can increase cold resistance and reduce the risk of colorectal and stomach cancers. Suggested intake, though not absolutely proven, is two raw cloves a day, plus garlic added to cooked foods several times a week.