Vitamin C

Most people don't think of vitamin C as a controversial nutrient. But when it comes to vitamin C supplements and the role they have in preventing or treating cold and flu and in giving you an immunity boost, they stir up considerable debate and conflict.

"The role vitamin C plays, with respect to the common cold, remains controversial," says Beth Isaac, PharmD, a staff pharmacist for Everyday Health. "There is very little evidence demonstrating that vitamin C has any significant effect on the common cold." The Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence, Isaac explains, and according to the National Institutes of Health, vitamin C is considered possibly effective for treating the common cold, but possibly ineffective for preventing the common cold. "Vitamin C may be effective for the common cold for specific types of people," she adds.

How Vitamin C Might Help

A review of 29 studies on vitamin C and cold and flu, involving more than 11,000 people, was conducted in 2007. After analyzing extensive data, the researchers concluded that there was no evidence that it prevented the common cold, and found only a slight amount of evidence that it reduced the duration and severity of colds. However, in five studies of people under extreme physical stress, like marathon runners and skiers, taking vitamin C appeared to reduce the occurrence of the common cold.

How Much Vitamin C Should You Take?

Though the information on vitamin C and the common cold is mixed, there are few risks in trying vitamin C and vitamin C supplements for reducing the severity or duration of cold and flu. However, Isaac doesn't recommend taking high doses of vitamin C every day — only while the cold is active. "The recommended daily allowance for vitamin C for adults is 90 milligrams for men and 75 milligrams for women, which you can get from a multivitamin," she says. "Based on scientific research, the dose for treating the common cold is 1 to 3 grams [1,000 to 3,000 milligrams] per day. Vitamin C is likely safe for most individuals when taken in recommended doses." High doses of vitamin C, greater than 2 grams per day, are considered possibly unsafe and may cause many unwanted side effects, including kidney stones, nausea, and diarrhea.

Getting Vitamin C From Foods

Vitamin C is just one of many antioxidants that you can get through food and that can play a healthy role in boosting your immunity. And though you won't get as high a dose of vitamin C from foods as you will from supplements, you will get a number of other healthy components, including other antioxidants and fiber, from eating whole fruits and vegetables. "Good sources of vitamin C include fresh fruits and vegetables, especially citrus fruits, tomatoes, potatoes and leafy vegetables," says Isaac. "Most experts recommend getting vitamin C through diet, rather than supplements."

Other Tips to Prevent Cold and Flu

Finally, it should come as no surprise that to boost immunity and prevent colds and flu this season, you'll need to do much more than eat foods rich in vitamin C or take a vitamin C supplement. Here's what else you can do:

* Wash your hands. David Tayloe, MD, a pediatrician in Goldsboro, N.C., a past president of the American Academy of Pediatrics, suggests washing with warm water and soap for at least 15 seconds or using an alcohol-based hand sanitizer that is at least 60 percent alcohol. And when your hands aren't being washed, keep them away from your face. "Hand washing is probably the best way for most of us to avoid getting common viral infections," says Dr. Tayloe.
* Get a good night's sleep. When you're not well rested, your immune system function suffers greatly. Strive for at least seven to nine hours of sleep a night.
* Clean and disinfect frequently. By using vinegar and common household cleaners, you can stop the spread of germs around your home. Focus on areas that are often touched by hands, like doorknobs, counters, and trash cans.
* Eat a healthy diet and exercise regularly. Both of these healthy habits have been shown to keep your immune system functioning at a higher level, Tayloe says.
* Get a flu shot. A flu shot will greatly reduce your chances of getting the flu, and lessen the severity of the flu if you do get it. Plus, you'll help protect others with weaker immune systems, such as infants and the elderly, from getting your flu.

Your best defense against the cold and flu is a healthy lifestyle, as well as these smart steps that will help boost your immune system.