A large body of evidence suggests that cancer rates and mortality increase under conditions of sub-optimal
selenium intake.5,8 In Linxian China, where selenium soil levels are known to be low, they have one of the highest
rates of esophageal and stomach cancer in the world.
In a five year study of almost 30,000 men and women (free from cancer at the outset of the study), supplementation
with beta-carotene, Vitamin E, and selenium reduced death rates from cancer by 13 percent, stomach cancer by 21
percent and death rates from all causes by 9 percent as compared to other vitamin and mineral combinations and
placebo.9 Death rates from lung cancer were 45 percent lower and there was a 10 percent reduction in strokes in
those receiving the combination of beta-carotene, vitamin E and selenium.10 Doses were 1-2 times the RDA.
In a clinical trial of over 1,300 patients with previous skin cancer, patients receiving 200 mcg of selenium
supplementation vs. placebo for 4.5 years had a 37 percent reduction in total cancer incidence and a 50 percent
lower risk for colorectal cancer and a 53 percent lower risk for lung cancer. However, the selenium group failed to
show benefit in blocking skin cancer recurrence or progression compared to the placebo group.11
In a recent study by Russo, et al., they showed that patients with selenium blood levels of 107 mcg/L had a 50
percent greater chance of having multiple cancerous lesions in the colon compared to patients referred for
colonoscopy, who had blood levels of selenium at or above 120 mcg/L. Other studies also indicate that higher
serum selenium levels are associated with as much as a 4.2 times lower risk of colon cancer.4
Another study found that men consuming the most dietary selenium (assessed by measuring toenail selenium, a
good indicator of long-term selenium ingestion) developed 65 percent fewer cases of advanced prostate cancer
than did men with the lowest selenium intake levels.12