Vitamin C for Prevention
Vitamin C plays a role in immune function and the maintenance of tissue integrity, both of which are important factors in the body’s response to infections. People with low or suboptimal vitamin C are likely to have a reduced capacity to ward off a viral infection in its earliest stages. More than half of U.S. adults are consuming less than the Recommended Daily Allowance (RDA) for vitamin C, and a little over 7% have vitamin C deficiency. For most people, supplementing with 200-500 mg per day of vitamin C would improve low or suboptimal vitamin C status. Cigarette smokers and people with chronic illnesses might need more than that to achieve an adequate amount. There is no evidence that taking multi-gram doses of Vitamin C is more effective for preventing infections.
Vitamin C levels have been reported to fall dramatically within 24 hours of the onset of a cold, presumably due to increased vitamin C utilization for tissue defense mechanisms. Multi-gram daily doses beginning at the first sign of illness appear to be needed to prevent this decline. While clinical trials indicate that 1.5-4.0 grams per day in divided doses can shorten the duration of symptoms caused by the common cold, anecdotal evidence suggests that much larger doses may be needed for the best results against viral infections. A “bowel- tolerance” dose – the dose just below that which produces diarrhea – is recommended by Dr. Robert Cathcart to treat viral illnesses. Patients are often able to tolerate much larger doses of vitamin C when they are ill than when they are well. As they improve, their bowel-tolerance limit decreases. High dose vitamin C is contraindicated in people with end-stage renal disease.
Terry Pfau DO, HMD