Top Ten Nutritional Strategies to Help
Optimize Your Immune Function

The Immune System: A Quick Overview
       In order to maintain your health and perform your best throughout the duration of a season, it's essential that you properly nourish your immune system. Your immune system only has a few lines of defense, so you better take care of them. The first is your skin and mucous membranes, which defend against invading bacteria and viruses. This is also known as humoral immunity. Without proper care, including an inadequate supply of essential nutrients provided by a well balanced diet, skin pores and mucous membranes can become enlarged, allowing disease-causing bacteria and viruses to easily enter the body, at which point your second line of defense, cellular immunity, kicks in. In order to fight off the bacteria and viruses that enter the body, some 10 million proteins called antibodies are produced each hour to help tag any pathogen, whether a virus, fungus, or cancer-prone cell, for destruction. White blood cells, also known as lymphocytes, are the main fighters within the cellular army and include B-cells and T-cells. B-cells, along with Helper T-cells, are responsible for producing and releasing the antibodies that identify the pathogen, while Killer T-cells make the deadly substances that actually destroy the pathogen. Suppressor T-cells help keep the immune system working efficiently, yet research has found that vigorous endurance exercise, such as marathon running, when combined with poor dietary habits actually compromises T-cell activity, allowing the pathogen to beat the cellular army and cause infection.
Fortunately, following proper nutritional strategies both at rest and during training will help keep your immune function running at peak. Below are ten nutritional strategies to help keep you running strong all season long.

10. Add Some Color to Your Diet
       Every meal plate should contain foods providing plenty of color, especially fruits and vegetables. Fruits and vegetables, particularly those with a deep hue, are loaded with antioxidants, which help protect our immune cells from harmful oxygen molecules called free radicals. Studies have found that individuals consuming a diet rich in antioxidants that includes at least 5 servings of fruits and vegetables each day, are able to produce more natural killer cells and virus-killing lymphocytes (which help reduce the incidence of infection by 50% each year), compared to those folks not so keen on color. Often the color of a fruit or vegetable will indicate what immune-enhancing nutrient is prevalent in the plant.

9. E-lectrify Your Diet
       Vitamin E, which is found naturally in almonds, wheat germ, avocados, whole grains, and vegetable oils, enhances the production of B-cells and stimulates the production of natural killer cells, helping to tackle everything from bacteria and viruses to cancer cells. Supplementation with vitamin E may also reverse some of the decline in immune response commonly seen in aging. Several studies have found that the recommended daily value for vitamin E, 30 IU, is rarely obtained from diet alone. Furthermore, higher doses of 100-400 IU seem to trigger a greater immune response.

8. Strengthen the Flavor of Your Next Meal with Garlic & Onion
       Garlic and onion contain the common compound allyl sulfide, which has been shown to increase levels of infection-fighting white blood cells, boost natural killer cell activity, and enhance the efficiency of antibody production. Many doctors recommend including one raw or cooked clove of garlic and one medium onion each day to help enhance immune function. Just remember to take that breath mint after the flavorful meal!

7. Boost Your Zinc Intake
       One of the most common nutritional deficiencies present among American adults, especially vegetarians, is zinc, which is unfortunate for the immune system. Zinc not only increases the production of white blood cells, which help recognize and destroy invading bacteria and viruses, it also helps enhance killer cell activity, reducing the risk of cancer and other infection. Zinc is found extensively in beef products; a mere 3-ounce serving of roast beef contains 30% of the Daily Value for zinc. For vegetarians and non-beef eaters, zinc can also be found in oysters, fortified cereals, crab, turkey, pork, yogurt, and beans. A moderate daily intake of zinc (15-25 mg) seems to be adequate to maintain optimal immune function.

6. Don't Overdo Fat
       An excessive intake of fat (>30% of total calorie intake), especially when derived primarily form such animal foods as beef, poultry (skin), butter, and whole milk, increases the production of harmful free radicals, which can diminish lymphocyte production and consequently increase risk for infection. On the flipside, a low-fat diet that focuses on inclusion of such plant fats as nuts, seeds, avocados, flaxseed, and olives as well as healthy fish oils helps to stimulate lymphocyte production and reduce risk for infection.

5.When Training >90 Minutes, Consume Carbohydrates, Both During and After the Activity
       Runners engaged in prolonged, intense activity seem to be at heightened risk for development of upper respiratory tract infections during the 2 hours immediately following the activity. The immune suppression seen in runners may be attributed to elevated levels of the stress hormone cortisol and a corresponding drop in lymphocyte production and T-cell activity seen after completion of hard training. Dr. David C. Nieman, exercise physiologist, has conducted much of the research looking at immune function in runners and has discovered that carbohydrate supplementation both during and immediately after intense, prolonged exercise helps reduce cortisol levels and maintain lymphocyte production, thereby helping prevent infection.
       Runners training longer than 90 minutes should aim at consuming ½ gram of carbohydrate per pound of body weight for each hour beyond the 90 minute mark of a run. For example, a 120-pound female runner should consume approximately 60 grams of carbohydrate per hour, which may be fulfilled by consuming an energy gel packet washed down with a sports drink every 30 minutes. Similarly, runners should consume approximately half their body weight in carbohydrate grams within 30 minutes of completion of any prolonged or intense training bout. For example, a 180-pound male runner should consume approximately 90 grams of carbohydrate, which would be equivalent to a large (4-ounce) bagel and a banana.

4. Don't Shy away from Fungus
       Mushrooms, especially shitake and maitake mushrooms, seem to increase the production and activity of white blood cells, allowing them to aggressively destroy pathogens. Most researchers have discovered this immune enhancing effect with a mere ½ cup serving. So at your next carbo-loading pasta meal, be sure to prepare your sauce with extra mushrooms!

3. Keep Your Blood Sugars Stable by Eating Small, Mixed Meals Every 3-4 hrs
Individuals whose blood sugars ride a yo-yo rollercoaster on a daily basis due to erratic eating patterns and food restriction are at heightened risk for infection due to suppression of immune activity. To prevent low blood sugar, aim at eating small meals consisting of carbohydrate and protein every 3-4 hours. Sample snacks / meals include low-fat granola (carbohydrate) with yogurt (protein), whole grain toast (carbohydrate) spread with almond butter (protein), rice (carbohydrate) and beans (protein), and pineapple chunks (carbohydrate) blended with low fat cottage cheese (protein).

2. Add Some "Culture" to Your Diet
       Consuming yogurt products that contain active cultures called probiotics seems to increase the amount of friendly bacteria that line the intestinal wall, helping to fight off germs that would otherwise enter and cause infection. In fact, several studies have found that daily consumption of a mere cup of yogurt containing "live and active cultures" helps to reduce the incidence of the common cold throughout the year. A higher dose (2 cups) of yogurt seems to further protect the body against viruses. The same benefits can be obtained by drinking a fermented milk drink called kefir. When possible, try to buy yogurt that is less than a week old to ensure reaping the most benefit from the active cultures.

1. Stay Hydrated
       Hydration is not only important for peak muscle function but also for protection against infection. Drinking half your body weight (in pounds) in fluid ounces on a daily basis will help wash away bacteria before they cause infection. For additional immune-enhancing benefits, include cranberry juice as part of your daily fluid intake. Cranberries are rich in flavonoids, which are powerful antioxidants that help boost immune function.

Kim Brown, MS, RD is a registered sports nutritionist and competitive endurance athlete who provides nutritional counseling and meal planning to athletes around the world.

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