Selenium, beta-carotene, and vitamin E combination in two trials:
Two randomized studies were conducted in Linxian, an area of north central China whose residents have very high rates of esophageal and stomach cancers. The first trial trial, enrolled 3,318 adults aged 40–69 years with esophageal dysplasia, a precursor to esophageal cancer. Trial participants were randomly assigned to receive either a placebo or a daily supplement of 14 vitamins and 12 minerals (including beta carotene, alpha-tocopherol, and selenium) at 2 to 3 times the US RDA for 6 years. This 6-year intervention was associated with a non-significant change: a 16% reduction in the esophageal cancer mortality rate. A second trial, randomly assigned 29,594 adults aged 40–69 years to receive 1 of 4 combinations of multivitamin supplements containing retinal and zinc, riboflavin and niacin, vitamin C and molybdenum, or β-carotene, vitamin E, and selenium each day for 5.25 years. Doses were equivalent to 1 to 2 times the US Recommended Dietary Allowances (RDAs). Results from the second trial showed that those who received the beta-carotene–vitamin E–selenium combination had a 13% reduction in cancer mortality, including a 21% decrease in stomach cancer mortality, a 41% decrease in gastric cancer mortality, and a 4% decrease in deaths from esophageal cancer. The findings indicate that vitamin and mineral supplementation of the diet of Linxian adults, particularly with the combination of beta-carotene, vitamin E, and selenium, may affect a reduction in cancer risk in this population. (9)