Vitamin A therapy chews on oral cancer.

Vitamin A therapy chews on oral cancer

Chewing tobacco or dipping snuff may be de rigueur in some circles, but oral cancer can devastate the lives of those with the habit. In recent years, scientists have looked at a possible role for vitamin A or its precursor beta carotene in reducing oral cancer risk, partly based on observations that oral cancer patients have low plasma levels of the vitamin. During preliminary studies in India among chewers of tobacco-containing betel quids, researchers at the British Columbia, Cancer Research Center in Vancouver have found various oral doses of vitamin A and beta carotene not only cause remission of precancerous areas called oral leukoplakias, but also prevent new lesions from forming.

Hans F. Stich and his co-workers report that weekly ingestion of 200,000 international units (IU) of vitamin A caused leukoplakia shrinkage in 12 of the 21 study participants given the vitamin alone. (The U.S. minimum daily requirement for the potentially toxic vitamin is 5,000 IU.) A smaller percentage of other betel chewers showed remission with a combination treatment of vitamin A and beta carotene, or beta carotene alone. Even more impressive is the observation that both compounds prevented the development of new leukoplakias during a year of treatment, the scientists say. Concerned that the doses used might prove toxic over long periods, the scientists are studying whether lower "maintenance" amounts can prevent new lesions after higher doses have shrunk established leukoplakias. Two other experiments are using beta-carotene-rich red palm oil as a possible preventive, in an attempt to avoid vitamin A toxicity.

Studying bovine papillomaviruses in mouse-cell cultures, the Vancouver group also discovered that a vitamin A relative called retinoic acid reduces viral DNA inside cells. The scientists say this suggests a possible mechanism for at least part of vitamin A's apparent anticancer potential, as human papillomaviruses have been found in precancerous and cancerous areas.