Selenium, Cancer and Longevity

Update: new research puts some doubt on the benefits of selenium and lung cancer prevention. A ten year study led by researchers at the MD Anderson Cancer Center showed no benefit in the prevention of lung cancer. Does that mean selenium is worthless? No -- it just means that it does not look helpful for lung cancer and more research will need to be done to determine other questions (new study source: presentation at the American Society of Clinical Oncology 2010 Annual Meeting by Daniel D. Karp, M.D). You may have heard of selenium as a longevity supplement. It is often promoted as a reducer of cancer and heart disease risk. It works by lessening the negative impact of free radicals in your body. Studies have shown that selenium levels are linked to a reduced risk of prostate and other cancers. However, there has been some contradictory information that extremely high levels of selenium may actually increase cancer risk.

Examining the Selenium, Cancer, Heart Disease and Longevity Link

To sort this out, researchers conducted a study of almost 14,000 adults. The study examined them selenium levels over 12 years and attempted to link those levels to the overall risk of death, death by cancer and death by heart disease. One of the things the study was trying to determine was if high levels of selenium lead to an increased risk of death.

Too Much of a Good Thing

Researchers found that higher (but not too high) levels of selenium were associated with a decrease in overall death rate and the death rate from cancer. They did not find a link between selenium level and heart disease. Researchers also found that individuals with selenium levels in the blood over 130 ng/ml were more likely to die of cancer. They conclude that moderate increases in selenium level can be linked to increased longevity through a decrease in the risk of cancer and overall death. However, extremely high levels of selenium are no longer helpful and may actually decrease longevity.

Selenium is found in seafood, grains, nuts and other dietary sources. Learn more about selenium as a supplement, its risks and side effects.

_Source:

Joachim Bleys, MD, MPH; Ana Navas-Acien, MD, PhD; Eliseo Guallar, MD, DrPH. Serum Selenium Levels and All-Cause, Cancer, and Cardiovascular Mortality Among US Adults. Arch Intern Med. 2008;168(4):404-410.

_{Karp D; A phase III, intergroup, randomized, double-blind, chemoprevention trial of selenium (Se) supplementation in resected stage I non-small cell lung cancer (NSCLC); American Society of Clinical Oncology, 2010 Annual Meeting.}