Vitamin C is often touted as a natural cold remedy. The nutrient is featured in supplements aimed at the immune system.
About vitamin C
Our bodies can’t make vitamin C, but we need it for protection of cells from oxidative stress.* It contributes to normal nervous system, psychological function, and helps reduce tiredness and fatigue through involvement in energy yielding metabolism.* Vitamin C contributes to normal collagen formation, and the normal function of bones, teeth, cartilage, gums and skin.* In regards to aiding the use and absorption of other nutrients, Vitamin C helps utilise vitamin E and increases iron absorption.*
We get vitamin C from our diet, usually in fruits and vegetables, but also potatoes provide a useful contribution to the diet. The recommended daily amount is 80mg per day in adults.
The impact on colds
The best evidence to date comes from a 2013 review of 29 randomised trials with more than 11,000 participants. Researchers found that among extremely active people—such as marathon runners, skiers, and Army troops doing heavy exercise in subarctic conditions—taking at least 200 mg of vitamin C every day appeared to cut the risk of getting a cold in half. But for the general population, taking daily vitamin C did not reduce the risk of getting a cold. So if you’re really active you may benefit from taking a vitamin C supplement all year round.
Taking at least 200 mg of vitamin C per day did appear to reduce the duration of cold symptoms by an average of 8% in adults and 14% in children, which translated to about one less day of illness. That could be really important for some people, since the common cold causes millions of lost days at work every year.
What you should do?
Should you take a supplement? Of course it’s better to get vitamin C from food, because you also get other important nutrients. Eat the recommended five servings of fruits and vegetables per day for general health, and you’ll get enough vitamin C to meet your 80mg target.
If you exercise vigorously or want to reduce cold duration you may need to take a supplement to get a higher dose. If you want the benefits of vitamin C, you’ll need to consume it every day, and not just at the start of cold symptoms.
What about claims that massive doses of vitamin C can help prevent a cold? Some studies have suggested there may be a benefit, but they required doses of 8,000 mg per day. The problems is that at doses above 400 mg, vitamin C is excreted in the urine- see our blog about Altruvita using sensible doses of vitamin C. A daily dose of 2,000 mg or more can cause nausea, diarrhoea, abdominal pain, and it may interfere with tests for blood sugar.
* EU REGISTERS ON NUTRITION AND HEALTH CLAIMS