Abstract
This article reviews possible preventive effects on cancer by micronutrients on the basis of worldwide epidemiological investigations in humans. Cohort and case-control studies indicate clearly that vegetable and fruit consumption decreases the risk for most sites of cancer. The risk reduction is observed not only for gastrointestinal tract cancers, but also for other sites (e.g. breast) of cancers. Consumption of vitamin C and β-carotene is related to risk reduction. Four large-scale randomized intervention studies have been reported. A study done in Linxian, China indicates that, among various micronutrients administered, β-carotene; vitamin E, and selenium reduced the risk of gastric cancer by 21%. However, a study on US male physicians showed no effects by β-carotene and two other studies on heavy smokers showed some elevated risk for lung cancer. Although more consumption of vegetables and fruits should be recommended to the general public for the prevention of cancer, further extensive investigations are needed to identify truly effective micronutrients contained in vegetables and fruits.
