By Donna Feldman, MS, RD

For decades, vitamin C has been connected to cancer prevention and treatment. The belief in vitamin C’s power as a nutritional supplement can be traced to the mid-20th century and Linus Pauling, a Nobel-prize winning chemist. Pauling’s interest in nutritional biology eventually led him to become one of the most prominent advocates for vitamin C as a cure for just about everything.

In the years since, vitamin C has been studied for its effect on cancer, the common cold, the flu, and numerous other diseases. The result? Every year, Americans spend more than $700 million on vitamin C supplements. Despite all the expense, however, cancer and the common cold have not been eliminated.

Vitamin C basics

Vitamin C is essential for human health in amounts that are small compared to those found in many supplements. It is essential for many physiological processes, notably collagen production and amino acid synthesis. It also has some antioxidant properties. The current intake recommended in the United States is between 60 to 95 milligrams, depending on age and gender. This amount is easily obtained by drinking a glass of orange juice. Excess intake is quickly excreted.

Vitamin C as a drug

Why would vitamin C have any effect on cancer beyond its normal metabolic role? The assumption is related to the vitamin’s antioxidant properties. As an antioxidant, it can act as a scavenger molecule, preventing oxidative damage by reacting with byproducts of cell metabolism. Oxidative damage to cells and DNA can result in cancer. These connections sound promising. Unfortunately, no studies have shown that vitamin C can either prevent or cure cancer. And there have been plenty of studies. The Institute of Medicine released a report a few years ago which reviewed over a thousand studies of vitamin C. The conclusion was that the vitamin has no preventive effect against cancer or any other chronic disease.

Promising new cancer research

Some researchers have recently revisited the idea of using vitamin C to treat cancer, but from a very different angle. Dr. Mark Levine at the National Institute of Health has studied the effect of using intravenous vitamin C for cancer patients and found promising results. With intravenous administration, very high blood levels can be achieved quickly—levels that are impossible to reach with supplements. At extremely high levels, the vitamin appears to boost production of hydrogen peroxide, which then kills cancer cells and spares the healthy cells.

Dr. Levine hopes more research on this use of vitamin C will continue. Until more research is completed, vitamin C administered intravenously will not be a standard cancer treatment. Attempting to recreate the effect by taking massive amounts of supplements will not work. In 1996, Dr. Levine conducted a study(1) which showed that a body’s cells can absorb only about 100 milligrams of vitamin C per day. Blood levels peak with supplemental amounts over 200 milligrams daily, as urinary excretion kicks in.

Conclusion: healthy but not yet proven as a miracle cancer cure

Despite the lack of evidence for vitamin C as a cancer fighter, an Internet search produces innumerable sites promoting and selling mega doses as a cancer cure. When the local vitamin store has a 20-foot row devoted to vitamin C that is 12 shelves high, you know popular demand is strong. New research on intravenous vitamin C is definitely intriguing, but not well understood. Until those results are in, vitamin C will remain important to human health for its original function—as a vitamin, but the myth of miracle cancer cure will likely persist.