Alpha-Tocopherol Reduces Upper GI Cancer Risk

BETHESDA, Md.--Serum alpha-tocopherol levels, but not gamma-tocopherol levels, may be associated with a reduced risk of upper gastrointestinal (GI) cancers, according to investigators at the Cancer Prevention Studies Branch of the Center for Cancer Research at the National Cancer Institute (NCI). Philip R. Taylor, M.D., Sc.D., and colleagues published their findings in the Sept. 17 issue of the Journal of the National Cancer Institute (95, 18:1414-16, 2003) (jnci.oupjournals.org).

According to the researchers, a prior study--the General Population Trial--indicated subjects in Linxian, China, taking beta-carotene and vitamin E supplements had significantly lower cancer mortality rates than those who did not take supplements. To further explore this data, Taylor and colleagues conducted a case-cohort study to investigate whether pre-trial serum vitamin E levels were associated with the risk of upper GI cancers, as Linxian residents have extraordinary rates of esophageal and gastric cardia cancers.

Researchers reviewed serum alpha- and gamma-tocopherol levels, as well as cholesterol levels, for 1,072 case participants and 1,053 control subjects. An analysis indicated those in the highest quartile of serum alpha-tocopherol levels were less likely to develop esophageal squamous cell carcinoma and slightly less likely to develop gastric cardia cancer than those in the lowest quartile. However, higher alpha-tocopherol levels were actually associated with an increased risk of gastric noncardia cancer than those in the lowest quartiles.

"As to why the results appear different for the different sites studied, I actually think the results for esophagus and cardia are very similar, and these are the real major cancers and causes of mortality in this population," Taylor told INSIDER. "Gastric non-cardia cancer has different primary causes, mainly Helicobacter pylori infection, and the number of cases of this disease in our population are really very small (less than 100) compared to the other two sites (more than 1,000), so chance findings are always more likely in small study populations."

The researchers also learned gamma-tocopherol was not associated with the incidence of any of the cancers studied, although Taylor noted gamma-tocopherol levels are almost always lower in blood and tissues than alpha-tocopherol, possibly due to less efficient absorption of the vitamin E isomer. Researchers concluded their findings support the role of alpha-tocopherol in the etiology of upper GI cancers.

"For the broader scientific community/world, we have to be cautious in generalizing the results from these studies, including the current study, to the rest of the world," Taylor added. "We do not know for sure that supplementation with these micronutrients in a well-nourished population such as is found in the West--as opposed to the poorly nourished population of Linxian--would provide similar reduction in risk. These data do, however, provide strong proof-of-principle evidence that nutrition is related to cancer overall, and they establish the paradigm that improving nutrition status in selected undernourished populations can reduce cancer rates."