Anticancer mineral works best in food

Selenium is an essential mineral that comes in many chemical forms. Although selenium-rich diets appear capable of protecting people against several cancers, a new federal study has found that selenium eaten as a pure compound may not protect as well as selenium consumed as a part of food.

John W. Finley of the Agricultural Department’s Grand Forks (N.D.) Human Nutrition Research Center enriched the diets of rats with selenium for 12 weeks. Some got selenomethionine, either in pure form or as a constituent of wheat. Others got methylated selenocysteine, in pure form or as a natural ingredient in high-selenium broccoli.

Three weeks into the trial, the nutritionists gave each animal a chemical that would cause colon cancer. Nine weeks later, they surveyed the rats for precancerous intestinal-surface features called aberrant crypts. Those rats getting the purified selenium additives had 50 percent more aberrant crypts than did rats getting selenium as part of the wheat or broccoli they ate. Indeed, rodents getting the purified additives had as many aberrant crypts as rats getting no extra selenium did.

Something in the whole foods must boost selenium’s anticancer property, Finley concludes. He’s now trying to find out what that something is.

Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.