C how much you need

Q: I read the eTip last week about the importance of vitamin C and how it can help prevent diabetes. But how do I know how much of it to take?

Dr. Wright: A few scientists who’ve seriously studied this question point out that, on an equivalent-weight basis with animals that synthesize their own vitamin C, healthy adult humans (if they could) would produce between 2 and 4 grams (2,000 to 4,000 milligrams) of vitamin C internally each day.

These sorts of comparisons give us general guidelines about appropriate baseline quantities, but, since we’re all individuals, I recommend an individualized approach, using feedback from your own body. It’s actually quite simple to determine with the following process: Slowly increase your supplemental vitamin C each day until you start getting excess gas or loose bowels. At that point, your body isn’t absorbing or able to use that quantity, so you should then back off to the largest amount that doesn’t produce loose bowels or excess gas.

Most adults I work with find their tolerance point (when they’re not ill or stressed) to be 3 to 6 grams daily. When illness occurs, however, that point frequently increases to at least 20 to 30 grams daily. Occasionally, people who’ve had severe viral illness have told me they’ve taken up to 100 grams daily for a day or two without any bowel problems at all. (Since vitamin C is water-soluble and rapidly used by our bodies, it’s a good idea to spread out your total dosage amount over at least two or three intervals daily when you’re healthy and as often as hourly when you’re ill.)

One note of caution: Individuals who have had calcium-oxalate kidney stones or who come from families who’ve had them should limit supplemental vitamin C to 1 gram daily unless they’re working with a health-care professional knowledgeable in nutritional therapy. There’s a remote possibility that more vitamin C will increase the production of oxalate in those individuals. Fortunately, however, it’s easy to test for this possibility, and the risk is very small.