“Vitamin C? It merely gives you expensive urine.”
Mark Levine, MD, laughs when asked if he takes a vitamin C supplement. A researcher at the National Institute of Diabetes and Digestive and Kidney Diseases, Dr. Levine has done meticulous studies of how the body uses vitamin C. Although some research indicates that it may protect against cancer, cardiovascular disease, age-related macular degeneration, and—most famously—the common cold, studies that isolate vitamin C from the diet generally don’t find that taking it alone protects against disease. “The best evidence for vitamin C comes from studies where people get it from fruits and vegetables,” Dr. Levine says. The benefits likely come from the interaction of a range of nutrients in C-rich foods such as citrus fruits, red and green peppers, broccoli, strawberries, and Brussels sprouts. While some evidence suggests that taking 200 mg or more of vitamin C a day might shorten a cold by a few hours—“12 hours at the most,” says Dr. Levine—popping a supplement after symptoms start does no good. What’s more, Dr. Levine’s research shows that the body tightly regulates vitamin C levels, so it’s futile to load up on the megadoses found in popular supplements. “The body works very hard to absorb low amounts of vitamin C,” Dr. Levine says. “But as the dose goes up, you absorb much less, and you excrete the extra vitamin C through your urine in a matter of hours.”
So should you take a supplement?
Probably not. Even amounts higher than the RDA of 90 mg for men and 75 mg for women are easy to get from your diet. In fact, only 6 percent of the population is deficient in vitamin C, according to the Centers for Disease Control and Prevention.
Next: If you eat fish twice a week, do you need omega-3 supplements?