Selenium is an oft-overlooked essential nutrient … and growing evidence suggests that this is an unhealthful oversight.
Last year, we reported on a study by renowned researcher Bruce Ames, Ph.D., who found that, the “… same set of age-related diseases and conditions, including cancer, heart disease, and immune dysfunction are … associated with modest Se [selenium] deficiency …”.
Dr. Ames, a longtime professor at the University of California, Berkeley, is best known as the inventor of the Ames Tests, used worldwide to gauge the carcinogenic potential of natural and synthetic chemicals.
More recently, he's focused on the role of essential micronutrients –vitamins, minerals, and omega-3 and -6 fatty acids – in aging and disease.
Six years ago, he proposed a new idea – called the “triage theory” – which holds that secondary functions of a micronutrient go unfulfilled when your diet doesn't supply more than you need for short-term survival.
For more on the triage theory and the essential role that selenium plays in the body's antioxidant network, see “Selenium Seen as Key Anti-Aging Ally” and “Magnesium Shortage Speeds Aging of America”.
Now, researchers from the Harvard School of Public Health (HSPH) have linked low selenium levels to risk of diabetes.
Harvard study links diabetes risk to selenium shortage
The Harvard team examined the toenail selenium levels of more than 7,000 women and men participating in the long-term Nurses' Health Study and Health Professionals Follow-Up Study (Park K et al. 2012). 
For both men and women, the researchers found the risk of developing diabetes was 24 percent lower among people with the highest levels of selenium, compared to those with the lowest levels.
However, the Harvard group noted that the study does not prove a connection, just an association, and that the diabetes-deterring effects of selenium, if any, are unknown.
Lead author Dariush Mozaffarian, M.D., advised people to get their selenium from foods rather than loading up on supplements (HSPH 2012).
It's better, he said, to acquire more of the mineral through increased intake of the best, healthiest food sources, which are ocean fish and whole grains grown in selenium-rich soils, such as those in the U.S. Midwest.
Seafood scores  high for selenium
Almost all ocean fish contains more selenium than mercury — a situation that protects against mercury's ill effects.
To learn more, see “Why is seafood so clearly safe, despite mercury?” on our Purity Story page.
The table below shows the average selenium content of, and seafood species. To put these amounts in context, the recommended daily allowance (RDA) for adults is 55 mcg:
Selenium* per 3.5 oz serving
Albacore Tuna (canned) - 60
Sardines (canned) - 53
Mackerel (canned) - 52
Halibut - 47
Sablefish - 47
Pollock - 47
King Salmon (chinook) - 47
King Crab - 40
Shrimp/Prawns - 40
Silver Salmon (coho) - 38
Sockeye Salmon (red) - 38
Cod - 38
Scallops - 28
Beef, cooked - 35
Turkey, light meat, roasted - 32
Bread, whole wheat, 1 slice - 10
*All figures are in micrograms (mcg) and come from the USDA or ODS/NIH.
  • Harvard School of Public Health (HSPH). Selenium-Rich Diet May Lower Type 2 Diabetes Risk. Accessed at
  • Park K, Rimm EB, Siscovick DS, Spiegelman D, Manson JE, Morris JS, Hu FB, Mozaffarian D. Toenail selenium and incidence of type 2 diabetes in u.s. Men and women. Diabetes Care. 2012 Jul;35(7):1544-51. Epub 2012 May 22. Accessed at