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Overloading on Vitamin C?

I drink Emergen-C often. I average 2-3 packets per day. My friend warned that too much vitamin C can cause kidney stones. I also take a multivitamin each day that also has vitamin C. How much vitamin C is too much?

Answer (Published 3/16/2009)

Since each serving of this product is advertised to provide 1,000 mg of vitamin C, you’re getting 2,000 to 3,000 mg daily. That’s a lot. It probably won’t hurt you – the risk of kidney stones is very low – but it won’t help you either.

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A water-soluble vitamin and powerful antioxidant, vitamin C also helps the body form and maintain connective tissue, including bones, blood vessels, and skin.

For the record, I used to recommend taking 2,000 to 6,000 mg of vitamin C daily (divided into three doses). However, in 1999 I lowered my recommendation to 200 to 500 mg (divided into two doses) after reviewing two well-designed studies showing that this amount of vitamin C more than saturates the body’s tissues, and thus is sufficient to protect against cancer, heart disease and other chronic illnesses. One of the studies that influenced my decision analyzed clinical trials published in the April 21, 1999 issue of the Journal of the American Medical Association. It concluded that 200 mg a day is the maximum amount of vitamin C that human cells can absorb, making higher dosing on a daily basis pointless.

The second study came from the Linus Pauling Institute (Pauling himself took 18,000 mg of C per day) and was published in the June 1999 issue of the American Journal of Clinical Nutrition. It identified a similar dose, 120 to 200 mg, as the optimal amount for reducing the risk of cardiovascular disease, cancer, cataracts and other chronic conditions.

I wouldn’t worry about the higher doses you’ve been getting. For those with extra oxidative stress, such as during a cold or flu, working in a smog-filled city, or living with a smoker, I often recommend an extra 1,000 mg. Vitamin C is water soluble, and the body can easily eliminate it. But you’re probably just wasting money taking these higher doses.

Vitamin C is abundant in fresh vegetables and fruits. The best food sources include citrus fruits, red pepper and sweet potato.

Andrew Weil, M.D.

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