Does Vitamin C Really Fight Colds? – Care2.com

Everyone knows that vitamin C helps you fight a cold, but does that mean it’s true? The short answer to this question is ‘maybe.’ Read on for the long answer!

There has been a lot of research on vitamin C and colds. A 2005 study published in the European Journal of Clinical Nutrition tracked participants for five years. There were two groups: a low dose and a high dose group. The 144 people low dose group took 50mg of vitamin C daily. In the high dose group, the other 161 took 500mg per day.

Related: 7 Ways Vitamin C Protects You from Heart Disease

When the people in the low and high dose groups got sick, there was no difference in the severity and duration of their colds. What did vary was how often they got sick. People in the high dose group got sick less often than the ones in the control group.

The results of the 2005 study seem to suggest that once you’re experiencing cold symptoms, it may be too late for vitamin C to make a difference. The authors noted that their results “should be interpreted with caution.” The study had some limitations. Participants who saw a difference were taking regular vitamin C supplements, but taking a 500mg supplement may not be a good idea. More on that below.

A 2013 study took an even larger-scale look at vitamin C’s cold-fighting power. This meta-analysis looked at 70 years of studies: 20 trials involving 11,306 total participants. The researchers concluded that people doing extreme exercise or exposed to extremely cold temperatures for short periods can benefit from taking a vitamin C supplement.

The analysis found some evidence that regularly supplementing with vitamin C may reduce the severity of colds, but it wasn’t replicated when people took it therapeutically—after they already had symptoms. However, the researchers also said that there were not very many therapeutic trials to look at, and more research is needed.

The conclusion of that study was basically “it can’t hurt.” Vitamin C is inexpensive and it could help. They suggest trying large doses of vitamin C at the onset of a cold to see whether it helps you.

Can you take too much vitamin C?

Vitamin  C is water-soluble, meaning that you can’t overdose on it like you can fat soluble vitamins. Your kidneys filter out excess vitamin C, and it exits your body when you pee. You can’t OD on vitamin C, but mega-dosing for long periods is still not a great idea.

Taking more than 1000mg of vitamin C per day for prolonged periods can cause kidney stones in some people, though it is pretty rare. If you’re supplementing, make sure you also consider how much dietary vitamin C you’re consuming. If you’re also eating vitamin C-rich food, you could end up taking too much. The National Institutes of Health (NIH) lists the upper limits for vitamin C consumption:

NIH Vitamin C Limits

According to the NIH, taking too much vitamin C can cause gastrointestinal symptoms: diarrhea, nausea and stomach cramps. It can also cause your body to store too much iron, which may lead to organ damage.

Does vitamin C help with colds?

So, does vitamin C really prevent colds, shorten cold duration, or lessen symptoms? It could, especially if you’re marathon training or spending a lot of time out in very cold weather. Otherwise, taking vitamin C regularly and eating more vitamin C-rich foods can’t hurt, as long as you’re not mega-dosing.

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Does vitamin C really prevent colds? Let's look at some of the research.

Image Credits: Vitamin C chart via the NIH; other images via Thinkstock.

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