August 8, 2007

You Ask, I Answer: Vitamin C

I know you said Vitamin C supplements don’t do much to prevent colds, but what about once you have a cold? Does taking Vitamin C help shorten the duration?

-- Angela Burgos

Grand Rapids, MI

When we tell someone we have a cold, the immediate response is usually, “take your liquids and lots of vitamin C!”

Is this fact or just a propagated myth?

Well, the latest meta-analysis (review of many existing studies) comes courtesy of Dr. Robert M Douglas of the Australian National University of Canberra’s National Centre for Epidemiology and Population Health, and Dr. Harri Hemila of Finland’s University of Helsinki’s Public Health Department.

Together, they reviewed 65 years’ worth of studies focusing on the relationship between vitamin C and the common cold. The conclusion? 200 milligrams of Vitamin C (approximately 300% of the daily recommended intake) did not shorten a cold when compared to a placebo.

Interestingly enough, extremely high doses of Vitamin C (8,000 milligrams) helped shorten the duration slightly.

Just how extreme is that dose? Eight thousand milligrams constitutes 11,400% of the daily recommended intake!

It’s worth noting that most vitamins and minerals have what’s called an upper tolerable intake, or a number that helps distinguish when too much can become dangerous. For Vitamin C, this is set at 2,000 milligrams.

Downing 8 grams of Vitamin C to basically make your cold last one day less is not recommended. Super dosages of Vitamin C often result in gastrointestinal distress, particularly diarrhea and nausea.

Additionally, continuous high intakes have been linked to an increased risk of developing kidney stones, since the breakdown of Vitamin C results in a waste product known as oxalate (which, when attached to calcium, forms kidney stones).

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