Will taking Vitamin C protect against a cold? 

The average U.S. adult catches between two and four cold viruses each year, according to the Centers for Disease Control and Prevention (CDC). While more than 200 viral strains can cause the common cold, the most common is the rhinovirus, which is responsible for 10 to 40 percent of all colds.

The good news is that cold infections — rhinovirus and other strains — typically resolve without the need for medical attention. Young children and the elderly have the highest risk of complications, but most people recover within 7 to 10 days. The bad news is that vaccination doesn’t offer immunity to cold infections. There are vaccines available to protect against the flu, but not the cold.

Vitamin C Megadose Explained

There’s some belief that taking a vitamin C megadose as a supplement can protect against the cold virus. A vitamin C megadose is defined as a dose of vitamin C that’s significantly greater than the Recommended Daily Allowance (RDA). The World Health Organization (WHO) currently recommends 45 milligrams of vitamin C daily for health adults, and 25 to 30 milligrams for children.

A vitamin C, megadose, however, may consist of several thousand milligrams daily. Linus Pauling, Nobel Peace Prize-winning chemist and pioneer of the vitamin C megadose, was said to have consumed up to 12,000 milligrams of vitamin C daily.

The Science Behind Vitamin C Megadoses

Vitamin C, also known as ascorbic acid and L-ascorbic acid, is a naturally occurring vitamin that’s found in a variety of foods, some of which include apples, oranges, blueberries, blackberries, cranberries, tomatoes, broccoli and peas. It’s well-tolerated by the human body, with approximately 70 to 90 percent being absorbed when taken orally at normal dosage levels. When consumed as a megadose, however, about 50 percent of vitamin C is absorbed.

Vitamin C Benefits

Vitamin C offers a wide range of health benefits, including lowering blood pressure, improving skin elasticity, treating lead toxicity, improving cataracts and strengthening the immune system. And because it’s touted as an immune booster, many people assume that large doses will protect against the common cold.

A Cochrane study conducted in 2007 found that vitamin C, at regular dosage, did not significantly reduce the risk of cold infections in the general population. It did, however, reduce rates of cold infections in highly active individuals, such as marathon runners, skiers and soldiers.

There are mixed findings regarding the effectiveness of vitamin C megadoses when taken to prevent and/or treat cold infections, however. A study of 800 students published in the Journal of Manipulative and Physiological Therapeutics found cold symptoms were 85 percent less severe in participants who consumed a vitamin C megadose. This was a relatively small study, consisting of just 463 young adults.

A separate study, published in the Medical Journal of Australia, found no significant differences in either severity or duration of cold infections between participants who took a low-dose of vitamin C and a megadose. The nonprofit organization AARP also published an article in which it debunked the myth that vitamin megadoses prevent or shorten illnesses.

Risks of Adverse Side Effects

Not only is its effectiveness questionable, but vitamin C megadoses have been linked to several adverse side effects, including diarrhea, iron overload, scurvy, kidney stones and tooth decay.

While vitamin C is certainly beneficial, a megadose isn’t the miracle wonder that many people claim. Following the recommended dosage will likely provide the same immune-strengthening effects as a megadose. If you want to further reduce your risk of catching a cold, follow the tips listed below.

Tips to Protect Against Cold Infections

  • Avoid or limit exposure to individuals who are infected with the cold virus.
  • Wash your hands for at least 20 seconds with soap and warm water regularly, especially after eating. This is the single most important step in protecting against colds and other infections.
  • Don’t touch your nose, mouth, eyes or face
  • Disinfect surfaces like doorknobs, counter tops, remote controls and telephones.
  • Eat more fruits and vegetables.
  • Drink plenty of water.
  • Get enough rest.

The basis on which the vitamin C megadose was invented is that higher doses translate into stronger effects. As several studies have found, though, a higher dose doesn’t offer improved benefits. If you decide to begin a vitamin C megadose regimen, consult with your primary care physician first.