Like any fighting force, the immune system army marches on its stomach. Immune system warriors need good, regular nourishment. Scientists have long recognized that people who live in poverty and are malnourished are more vulnerable to infectious diseases. Whether the increased rate of disease is caused by malnutrition’s effect on the immune system, however, is not certain. There are still relatively few studies of the effects of nutrition on the immune system of humans, and even fewer studies that tie the effects of nutrition directly to the development (versus the treatment) of diseases.
There are studies of the effects of nutritional changes on the immune systems of animals, but again there are few studies that address the development of diseases in animals as a result of changes in immunity. For example, one group of investigators has found that in mice, diets deficient in protein reduce both the numbers and function of T cells and macrophages and also reduce the production of immunoglobulin A (IgA) antibody.
There is some evidence that various micronutrient deficiencies — for example, deficiencies of zinc, selenium, iron, copper, folic acid, and vitamins A, B6, C, and E — alter immune responses in animals, as measured in the test tube. However, the impact of these immune system changes on the health of animals is less clear, and the effect of similar deficiencies on the human immune response has yet to be assessed. But the research at this stage is promising, at least for some of the micronutrients.
Below is a list of Power Foods:
For centuries, people around the world have turned to mushrooms for a healthy immune system. Contemporary researchers now know why. “Studies show that mushrooms increase the production and activity of white blood cells, making them more aggressive. This is a good thing when you have an infection,” says Douglas Schar, DipPhyt, MCPP, MNIMH, director of the Institute of Herbal Medicine in Washington, DC.
Your optimal dose: Shiitake, maitake, and reishi mushrooms appear to pack the biggest immunity punch; experts recommend at least ¼ ounce to 1 ounce a few times a day for maximum immune benefits. Add a handful to pasta sauce, sauté with a little oil and add to eggs, or heap triple-decker style on a frozen pizza.
You may not think of skin as part of your immune system. But this crucial organ, covering an impressive 16 square feet, serves as a first-line fortress against bacteria, viruses, and other undesirables. To stay strong and healthy, your skin needs vitamin A. “Vitamin A plays a major role in the production of connective tissue, a key component of skin,” explains Prevention advisor David Katz, MD, director of the Yale-Griffin Prevention Research Center in Derby, CT. One of the best ways to get vitamin A into your diet is from foods containing beta-carotene (like sweet potatoes), which your body turns into vitamin A.
Your optimal dose: A half-cup serving, which delivers only 170 calories but 40% of the DV of vitamin A as beta-carotene. They’re so good, you might want to save them for dessert! Think orange when looking for other foods rich in beta-carotene: carrots, squash, canned pumpkin, and cantaloupe.
Zinc deficiency is one of the most common nutritional shortfalls among American adults, especially for vegetarians and those who’ve cut back on beef, a prime source of this immunity-bolstering mineral. And that’s unfortunate, because even mild zinc deficiency can increase your risk of infection. Zinc in your diet is very important for the development of white blood cells, the intrepid immune system cells that recognize and destroy invading bacteria, viruses, and assorted other bad guys, says William Boisvert, PhD, an expert in nutrition and immunity at The Scripps Research Institute in La Jolla, CA.
Your optimal dose: A 3-oz serving of lean beef provides about 30% of the Daily Value (DV) for zinc. That’s often enough to make the difference between deficient and sufficient. Not a beef person? Try zinc-rich oysters, fortified cereals, pork, poultry, yogurt, or milk.
People who drank 5 cups a day of black tea for 2 weeks had 10 times more virus-fighting interferon in their blood than others who drank a placebo hot drink, in a Harvard study. The amino acid that’s responsible for this immune boost, L-theanine, is abundant in both black and green tea—decaf versions have it, too.
Your optimal dose: Several cups daily. To get up to five times more antioxidants from your tea bags, bob them up and down while you brew.
When University of Nebraska researchers tested 13 brands, they found that all but one (chicken-flavored ramen noodles) blocked the migration of inflammatory white cells—an important finding, because cold symptoms are a response to the cells’ accumulation in the bronchial tubes. The amino acid cysteine, released from chicken during cooking, chemically resembles the bronchitis drug acetylcysteine, which may explain the results. The soup’s salty broth keeps mucus thin the same way cough medicines do. Added spices, such as garlic and onions, can increase soup’s immune-boosting power.
Your optimal dose: Have a bowl when feeling crummy. (Give this delicious recipe a try!)
Selenium, plentiful in shellfish such as oysters, lobsters, crabs, and clams, helps white blood cells produce cytokines—proteins that help clear flu viruses out of the body. Salmon, mackerel, and herring are rich in omega-3 fats, which reduce inflammation, increasing airflow and protecting lungs from colds and respiratory infections.
Your optimal dose: Two servings a week (unless you’re pregnant or planning to be).
This potent onion relative contains the active ingredient allicin, which fights infection and bacteria. British researchers gave 146 people either a placebo or a garlic extract for 12 weeks; the garlic takers were two-thirds less likely to catch a cold. Other studies suggest that garlic lovers who chow more than six cloves a week have a 30% lower rate of colorectal cancer and a 50% lower rate of stomach cancer.
Your optimal dose: Two raw cloves a day and add crushed garlic to your cooking several times a week.
Oats and Barley
These grains contain beta-glucan, a type of fiber with antimicrobial and antioxidant capabilities more potent than echinacea, reports a Norwegian study. When animals eat this compound, they’re less likely to contract influenza, herpes, even anthrax; in humans, it boosts immunity, speeds wound healing, and may help antibiotics work better.
Your optimal dose: At least one in your three daily servings of whole grains.
Probiotics, or the “live active cultures” found in yogurt, are healthy bacteria that keep the gut and intestinal tract free of disease-causing germs. Although they’re available in supplement form, a study from the University of Vienna in Austria found that a daily 7-ounce dose of yogurt was just as effective in boosting immunity as popping pills. In an 80-day Swedish study of 181 factory employees, those who drank a daily supplement of Lactobacillus reuteri—a specific probiotic that appears to stimulate white blood cells—took 33% fewer sick days than those given a placebo. Any yogurt with a “Live and Active Cultures” seal contains some beneficial bugs, but Stonyfield Farm is the only US brand that contains this specific strain.
Your optimal dose: Two 6-ounce servings a day.
Let’s not just choose one type though! A blend of nuts and seeds are high in fiber, dietery phenols and protein that nourish probiotics, the good bacteria that live in our digestive system. And, thanks to recent studies, we now know that to have a robust immune system we need to have a healthy digestive system.
Your optimal dose: 1.5 ounces (about 3 tablespoons) a day
More Power Foods:
Kale tops the list of immune boosters for many reasons. Here are just of few – it is high in fiber with 49 different flavonoids, tons of antioxidants, and loaded with vitamins C and K; two powerful vitamins that does so much to keep our bodies humming they’re too numerous to name here. Take our word for it; your immune system will thank you if you make Kale a staple on your grocery list. Find out more about Kale.
Cinnamon does more than boost the immune system. It actually fights the pathogens that cause illness. Cinnamon is one of the easiest nutrient rich foods to add to your diet. It enhances the flavor of coffee, perks up your morning oatmeal and livens up the taste of fresh fruit. It is also on the Super Food list for foods that help to prevent diabetes.
Cauliflower is an underdog of the cruciferous family that gets overlooked for its health benefits simply because it lacks the chlorophyll-induced color. It is on the immune boosting list because it is rich in glutathione, an essential molecule Mark Hyman, M.D. an internationally recognized authority in the field of Functional Medicine calls the secret to prevent aging, cancer, heart disease, dementia and more. The good news for women is that it also contains indole-3-carbinol, a substance that enhances estrogen metabolism.
To complete your immune boosting plan, do some moderate exercise, get plenty of rest and find creative ways to add more of these super foods into your diet.