Boosting Immunity Through Nutrition
When your co-workers or family members start coughing and sneezing, do you head for the medicine cabinet for one of those immune system-boosting supplements? When you get on an airplane do you take one of those fizzing tablets that is supposed to ward off airborne germs? You may find more success in making careful food choices everyday.
Eating a variety of nutrient-rich foods regularly helps build and maintain a strong immune system. Your immune system is a very complex collection of cells and tissues that protect your body from allergens, bacteria, viruses and other potentially harmful antigens (any foreign substance that produces an immune response). Your skin and membranes lining the body’s entrances (eyes, nasal passages, respiratory system, and digestive tract) provide physical barriers while specialized white blood cells battle antigens that make it inside. These cells include:
- T-lymphocytes—constantly are on patrol in search of antigens. There are several types of these T cells: Killer, Helper and Suppressor T cells. Killer T cells can detect and kill cells in the body harboring viruses. Helper and Suppressor T cells assist by sensitizing Killer T cells and controlling the immune response.
- B-lymphocytes—make antibodies, special proteins in the blood that destroy or neutralize germs.
- Neutrophils—by far the most common form of white blood cells in the body. The bone marrow makes trillions of them daily, but they have a short life span. They are attracted to foreign material, inflammation and bacteria. They engulf the foreign particles or bacteria, releasing enzymes, hydrogen peroxide and other chemicals to kill the bacteria. In the case of a serious infection, pus will form. This is simply dead neutrophils and other debris.
- Macrophages—these are the biggest blood cells. One of their jobs is to clean up dead neutrophils. Macrophages in the lungs also remove dust, smoke and necrotic debris. They are scavengers, and rid the body of worn-out cells and debris. Macrophages also provide a line of defense against tumor cells and body cells infected with fungus and parasites.
To work at maximum efficiency, these white blood cells need you to keep your body in great shape.
A balanced diet is the first key to the immune system’s optimal performance. Essential nutrients are crucial for the production and maintenance of key germ-fighting cells. And these cells can’t do their work without good blood flow, so maintaining an excellent cardiovascular system is vital too.
In particular, essential nutrients, antioxidants and minerals beneficial to the immune system are vitamin C, vitamin E, carotenoids, folate, vitamin B6, flavoniods, omega-3 fatty acids, selenium and zinc. Use the chart below to find functions and sources of these.
Immune System and/or Cardiovascular System Function
Key Food Sources
|This antioxidant may help neutralize free radicals that damage cells and tissues. (Free radicals are natural by-products of oxygen metabolism that are thought to contribute to the development of chronic diseases such as heart disease and cancer.) Increases the production of white blood cells and antibodies. May help raise levels of HDL (good) cholesterol and lower blood pressure.
||Citrus fruits (oranges, grapefruits, tangerines) papaya, kiwi, bell peppers, guava, strawberries, broccoli, potatoes, cabbage, tomatoes.|
||Enhances the production of B-lymphocytes. May also reverse some of the decline in immune response commonly seen in aging and may lower risk of cardiovascular disease. Also works as an antioxidant to protect cells from free radical damage.
||Nuts (especially almonds and hazelnuts), vegetable oils, seeds, wheat germ, spinach and other dark green leafy vegetables. |
||The most familiar of carotenoids is beta carotene, which increases the number of infection fighting cells and is a powerful antioxidant. Also interferes with the process by which fats and cholesterol clog arteries, thus lowering risk of cardiovascular disease. Beta carotene also stimulates macrophages to produce powerful cancer fighting substances. Beta carotene is only one member of a large family of carotenoids, which work together for these benefits. The body converts beta carotene to Vitamin A, of which too much can be toxic to the body. So it’s best to get beta carotene from foods and let the body regulate how much is converted to Vitamin A.
||Dark green vegetables and yellow/orange fruits and vegetables, such as broccoli, spinach, turnip greens, carrots, squash, sweet potatoes, pumpkin, apricots and cantaloupe. Animal sources include liver, milk, butter, cheese and whole eggs. The addition of small amounts of fats increases beta carotene absorption, as does cooking. Chopping and pureeing vegetables may also improve bioavailability. |
||Water soluble B vitamin. May help reduce homocysteine levels in the blood. High homocysteine levels may lead to inflammation, which is associated with higher risk of coronary artery disease. Adequate folate may reduce risk of certain forms of cancer and is essential for young women for preventing spinal birth defects.
Folate helps produce and maintain new cells. It also helps prevent changes to DNA (a building block of cells) that may lead to cancer.
|Think “foliage” such as leafy green vegetables (spinach), oranges, avocados, legumes, liver, yeast breads, wheat germ, and some fortified products (cereals, juices, rice, pasta). Most enriched grain products have folate added. |
||Water soluble vitamin. Necessary to maintain health of lymphoid organs that produce infection fighting white blood cells.
||Chicken, fish, pork, liver, and kidney are best sources. Nuts, legumes and whole grains also contain good amounts. |
||Many perform as antioxidants, playing a role to reduce risk of cancer, heart disease and other serious health problems. Protect the body’s cells against environmental pollutants.
||Colorful fruits such as blueberries, cranberries, red grapes, oranges, pink grapefruit, strawberries. Also teas (green and black), soy, dark chocolate, red wine. |
|Omega-3 Fatty Acids
||These beneficial fats increase the activity of macrophages and neutrophils. May lower risk of cardiovascular disease by decreasing triglyceride levels, decreasing growth rate of atherosclerotic plaques (clogs in the arteries), and by slightly lowering blood pressure.
||Fatty fish such as salmon, mackerel, sardines, herring, trout, albacore tuna. Flax seed, wheat germ, walnuts, pumpkin seeds, canola and soybean oils. |
||This trace mineral mobilizes cancer-fighting cells and increases the natural killer cells. Selenium is incorporated into certain proteins to make selenoproteins, which are important antioxidant enzymes. They help prevent cellular damage from free radicals.
||Fish, shellfish, red meat, grains, eggs, chicken, garlic, walnuts. Brazil nuts are the most concentrated source of selenium, but use caution as it is possible to reach toxic levels if too much is consumed. |
||Increases the number of T-lymphocyte cells. Helps white blood cells fight more aggressively. Helps B-lymphocyte cells release more antibodies. There is much hype about zinc supplements, as there are conflicting studies. Too much zinc from supplements may inhibit immune function, so it’s best to get adequate zinc from foods.
||Oysters contain the highest amount of zinc per serving, but the majority of Americans’ dietary zinc comes from red meat and poultry. Beans, nuts, some seafood, whole grains, fortified cereals and dairy products are good sources. Absorption is greater from diets rich in animal proteins than diets higher in plant proteins. Phytates, found in whole grain breads, cereals and legumes, can decrease zinc absorption. |
It is important to remember that in addition to choosing the right foods, cooking methods should also be considered. Some vitamins, including the B vitamins (especially folate) and vitamin C, are sensitive to heat and air, and can be lost in cooking water. Saladmaster cookware can help preserve these precious nutrients as foods can be prepared with little or no water and cooked at a lower temperature for a shorter period of time.
In addition to making wise food choices, other practices that could have a positive impact on your immune system include:
- Maintain a healthy weight
- Get enough exercise
- Minimize stress
- Get plenty of sleep
- Wash your hands
- Avoid alcohol and cigarettes
- Avoid excessive exposure to sun
- Avoid exposure to toxic chemicals and pollutants
- Limit intake of “empty calorie” foods (those high in sugar and fat) as they leave less room for nutrient dense foods.
About the author: Janet has been a registered dietitian since 1984 and a Saladmaster owner since 1995. In 1996 she was awarded the ADA’s "Recognized Young Dietitian" for the state of Oklahoma. In the year 2000, Janet was promoted to Director of Food & Nutrition Services at St. John Medical Center in Tulsa and has recently completed four years of service on the Board of Directors for the National Society for Healthcare Foodservice Management. She lives in Tulsa with her husband and two young children.
[PRINTER FRIENDLY VERSION]