Nutrition and Immunity: Staying Well All Winter

As we look outside and see the trees shedding their leaves, we all know that the white fluffy snow is right around the corner. Many of us can not help but think that the cold and flu season has arrived. But wait! There are some things you can do nutritionally that might help prevent you from catching whatever “bug” may be going around. Now, these are not cures and I am not going to tell you that this is a fool proof prevention method….but these things might help you stay well (or recover sooner) during this chilly season.

Colds are usually caused by the rhinovirus. This type of virus changes rapidly. In fact, the cold that you see going around one week is probably different than one going around two weeks later, yikes! Because of the new strain of the virus, the immunity that has been acquired because of the first one is not going to prevent you from catching the second one.  This is what makes it essential to have a strong immune system that is if you don’t want to be sniffly and achy all winter long.

The best way to keep your immune system strong is to consistently eat a well balanced diet, ensuring that you get adequate amounts of different nutrients. Malnutrition, in general, compromises immunity (which can include restrictive diets). However, there are a few important nutrients that are worth pointing out in regards to their role in immunity and prevention.

Protein
Function in immunity: Protein is an essential nutrient for the body. The immune response is triggered by the body recognizing something foreign (an antigen) on the surface of a cell that is unusual. The part of your body that recognizes antigens as "normal" or "alarming" is an antibody. Antibodies are specific proteins. Thus, protein in the diet is important for providing the building blocks to make these antibodies.

Food Sources: meat sources (poultry, pork, beef, etc.), fish, dairy products (milk, yogurt, cheese), eggs, soy foods, legumes, beans and nuts.

Beta-carotene & Vitamin A
Function in immunity: Beta-carotene is that red-orange pigment found in a variety of fruits and vegetables. The body converts beta-carotene into Vitamin A which is important in overall immune function. Beta-carotene (and all carotenoids) is important for its antioxidant function, protecting cells from damage caused by free radicals in the body. Free radicals are a result of oxidative stress placed on the body (such as toxins in air, food and water; tobacco smoke and radiation). Therefore, anti-oxidants, such as beta-carotene, are important in defending the body from this damage. Vitamin A is important as it enhances our resistance to infection by having a special role in enhancing white blood cell function.

Food Sources: sweet potato, carrots, squash, pumpkin, peppers, and leafy green vegetables such as spinach
Preformed vitamin A is found in foods from animal sources, including dairy products, fish, and meat 

Vitamin C
Function in immunity: Vitamin C is an antioxidant (like beta-carotene) and used to strengthen blood vessel walls.

Food Sources: citrus fruits, broccoli, green & red bell peppers, berries, leafy green veggies (spinach, cabbage, etc)

Vitamin E
Function in immunity: Vitamin E is an antioxidant helping to protect cells from damage. The body also needs vitamin E to boost its immune system as it helps widen blood vessels and keeps blood from clotting within them, thus helping to fight off invading bacteria and viruses. 

Food Sources: vegetable oils, nuts, seeds, green leafy vegetables

Zinc
Function in immunity: Zinc helps regulates immune function and it causes expansion of the immune cells.

Food Sources: foods high in protein, such as beef, poultry and fish.

Selenium
Function in immunity: Selenium is an antioxidant and greatly influences inflammation and immune responses.

Food Sources: brazil nuts and some types of fish, halibut and tuna

The above list of food sources is not exhaustive in any way as many nutrients have a role in keeping our immune system strong.  For example, folate, fatty acids, iron and vitamin B6 also function in immunity.  The important thing to remember is that optimal immunity depends on optimal nutrition – having enough, but not too much, of each of the nutrients.  Balance, Variety and Moderation may be the best mantra to keep you healthy this winter season.

Contributed by Laura Gaffney, University of Northwestern- St. Paul

---