Some of the most common viral infections are colds and flu. Other viruses affect the skin, causing warts, or the digestive system, causing stomach flu. Many childhood diseases are also caused by viruses. A weak immune system increases susceptibility to a variety of illness, including infections with viruses. Vitamins that enhance immune system function, such as vitamin D, C and A, may help prevent or decrease symptoms of viral infections.
In a clinical study published in June 2010 in Medical News Today, Dr. James R. Sabetta and colleagues found that vitamin D may help decrease the incidence and severity of respiratory tract infections caused by viruses, including influenza. The researchers suggest that supplementing with vitamin D to achieve a blood level of 38 nanograms per milliliter or higher may reduce the incidence of viral infections of the respiratory tract. The scientists believe that further research is needed to prove the effectiveness of vitamin D supplementation in the prevention of respiratory infections.
Vitamin C is an immune-enhancing vitamin and may help prevent viral infections such as colds and flu or childhood diseases. In the January issue of "Scandinavian Journal of Infectious Diseases," a review of 21 clinical trials using 1 to 8g of vitamin C daily showed that this vitamin decreased the duration of episodes and the severity of symptoms of common cold by approximately 23 percent.
A review of data from 30 studies, published in the July 2004 issue of "Cochrane Database" by R.M. Douglas and associates was designed to assess the effects of taking 200mg or more daily of vitamin C for prevention and treating the cold. The researchers concluded that in the general population, vitamin C did not decrease the risk of acquiring the cold. However, people who were taking vitamin C when they caught a cold experienced slight reductions in the duration and severity of their symptoms, compared to placebo group. According to Dr. James Balch, author of "Prescriptions for Nutritional Healing," adequate daily vitamin C intake is the most essential vitamin in maintaining effective immunity against the viruses that cause colds and flu, warts and children's diseases such as chicken pox.
Vitamin A is mostly known for its benefits in preventing blindness and eye problems, as well as some skin disorders. Vitamin A is also a powerful antioxidant nutrient that helps heal inflamed mucus membranes and strengthens the immune system. By enhancing immunity, vitamin A may help heal gastric ulcers and repair the skin and mucus membranes of the digestive tract. According to Balch, vitamin A is also important in the formation of the bones and teeth and may protect against colds, flu and infections of the kidneys, bladder and lungs.