BETHESDA, MARYLAND. Several large studies have found a clear association between low selenium levels and an increased risk of cancer. A major clinical trial involving supplementation with 200 micrograms/day of selenium (500 mg of high selenium brewer's yeast) was carried out in the United States in 1995. This trial concluded that selenium supplementation reduced overall cancer incidence by 40 per cent and cancer mortality by 50 per cent.
Researchers from the National Cancer Institute and the Chinese Academy of Medical Sciences in Beijing now report that selenium deficient individuals are more likely to develop cancer of the esophagus and stomach than are individuals with adequate levels. Their study involved 590 patients with esophageal cancer, 402 with gastric cardia cancers (cancers located close to the junction between the esophagus and the stomach), and 87 with gastric non-cardia cancers as well as 1062 cancer-free control subjects.
All participants had provided blood samples in 1985 prior to participating in
the large Linxian study that investigated the benefits of various supplements in
stomach cancer prevention. The researchers found that participants with blood
serum levels of selenium at or above 90 micrograms/liter had a 44 per cent lower
risk of developing esophageal cancer and a 53 per cent reduction in gastric
cardia cancer risk when compared to participants with levels at or below 50
micrograms/liter. There was no correlation between selenium levels and the
incidence of gastric non-cardia cancers. The researchers conclude that even
individuals in the highest quartile (upper quarter) of selenium levels could
benefit from selenium supplementation and that a supplement of 50 micrograms/day
is not enough to correct a long-term deficiency.