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Harvard Study Links Higher Selenium Levels To Lower Diabetes

by Craig Weatherby

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.
Seafood scores
high for selenium
Ocean fish is rich in selenium … which also nixes the effects of mercury.
To learn why, see “Why is seafood so clearly safe, despite mercury?” on our Purity Story page.
All figures below are in micrograms (mcg) and come from the USDA or ODS/NIH.
The adult RDA 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
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.
For information on the oceanic sources, see our sidebar, “Seafood scores high for selenium”.
Too much of a good thing?
One population study has linked high selenium blood levels to increased risk of diabletes (Laclaustra M et al. 2009).
And five years ago, the results of a randomized, double-blind, placebo-controlled clinical trial involving 1,202 people seemed to confirm concerns about high selenium intake from supplements.
The results showed that those who took a 200mcg (microgram) selenium supplement daily for almost eight years were 50 percent more likely to develop type 2 diabetes, versus those in the placebo group (Stranges S et al. 2007).
The risk of developing diabetes was higher in people who had higher blood selenium levels at the start of the study.
About 60 percent of Americans take multivitamin pills, many of which contain between 33 and 200mcg of selenium. For people aged 14 and over, the RDA (recommended dietary allowance) for selenium is 55 micrograms.
Most ocean fish are rich in selenium (see our sidebar “Seafood scores high for selenium”), and selenium levels in the soil of America’s Midwest breadbasket are quite high.
The bottom line is that people who eat significant amounts of U.S-grown grains and/or ocean fish probably should not take supplemental selenium in addition to a typical multivitamin supplement.

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