Influenza, more commonly known as the flu, is a viral infection that affects your upper respiratory system, causing symptoms such as congestion, cough, headache, fever, chills and fatigue. It is a highly contagious illness and is spread through the air and by touching contaminated surfaces. Although vitamins may not cure the flu, they may help bolster immune system function, reducing your risk of contracting an influenza infection. Check with your doctor before increasing your vitamin intake to prevent the flu.
Vitamin C is among the best known immune system-enhancing vitamins available. This vitamin may stimulate your body's production of interferon, a chemical that helps destroy viral infections, according to Phyllis Balch, author of "Prescription for Nutritional Healing." It also may increase white blood cell count, protecting your body against influenza infection. Boost your intake of vitamin C by adding foods to your diet such as kiwi fruit, pomegranates, blueberries, strawberries, spinach, limes, lemons and oranges. Because your body requires large doses of vitamin C to ward off influenza, as much as 10,000 milligrams per day, consider a vitamin supplement to further increase your vitamin C intake.
Vitamin B-5, also known as pantothenic acid, may stimulate the production of adrenal glands, providing your body with hormones for enhanced immune system response. It also may increase production of antibodies that attack and destroy the influenza virus, according to Balch. Vitamin B-5 also improves metabolism of carbohydrates and proteins from food sources that your body uses for energy and immune system health. This vitamin is found in B-complex vitamin supplements, as well as foods such as mushrooms, rye, whole wheat bread and garbanzo beans.
Vitamin D is an essential vitamin that your body produces when your skin is exposed to ultraviolet rays from the sun. However, this vitamin also is available in supplement form as well as from food sources such as eggs, dairy products, tuna, salmon, mackerel and halibut. This vitamin may enhance your immune system's ability to produce proteins that fight disease-producing microbes, according to the Harvard School of Public Health. However, evidence linking vitamin D to protection from influenza is largely anecdotal.
Like vitamin C, vitamin A may stimulate the production of white blood cells that destroy the influenza virus. It also is a potent antioxidant, which may prevent damage to your upper respiratory tract caused by toxins and free radical cells. Vitamin A is typically included in multivitamin supplements and also is available as a stand-alone supplement. You can boost your vitamin A intake by consuming foods such as carrots, beef liver, broccoli, cantaloupe, dandelion greens, cayenne peppers and alfalfa. Check with your doctor before increasing your vitamin A intake to ward off the flu since daily doses of more than 10,000 International Units may be toxic to your liver.