Tuesday, March 27, 2007

Selenium and Weight Gain

Feeling sluggish? Having difficulty losing weight? Or maybe you've been gaining weight without increasing what you eat? You might want to check your supplements. Or your rice if it was grown in selenium-rich soil. In the study I'm about to describe, healthy men who were fed between 200 and 300 micrograms of selenium daily (5 times the RDA, or the amount in a typical supplement) gained weight without increasing their caloric intake.

For years I've written about the risks of consuming too little of this or that nutrient. Lately, I find myself writing more about the risks of consuming too much. What does this say about America in the 21st Century?

Here we go...

The study appeared in the Journal of Nutrition in November 2003. It was funded by the USDA's Agricultural Research Service:

Dietary Selenium Intake Modulates Thyroid Hormone and Energy Metabolism in Men


Eleven healthy adult men were confined to a metabolic research unit and fed a controlled diet of conventional foods (not supplements) for 120 days. For the first 21 days, all 11 men consumed foods that provided 47 mcg/d selenium (RDA is 55 mcg). For the remaining 99 days, 6 men consumed calorie-equivalent foods that were naturally low in selenium (providing about 14 mcg/d), and 5 men consumed calorie-equivalent foods that were naturally high in selenium (providing about 297 mcg/d).


The men in the high selenium group experienced:
  • Decreased levels of selenium-dependant thyroid hormone (T3).
  • Increased body weight.
  • Increased fat mass.
The men in the low selenium group experienced:
  • Increased levels of selenium-dependant thyroid hormone (T3).
  • Decreased body weight.
  • Decreased fat mass.
Here are these men's weight changes (To convert kg to lbs, multiply by 2.2.):

The authors speculate:
"... a simple extrapolation suggests that if the effect of high dietary selenium were to persist, it could cause a weight gain of up to 12 kg (26.4 lbs) in 5 years."
A drawback to this study is the small population size: 11 men. However, the study's methods more than made up for the small population size. Unlike the recently-discussed diet study where women reported their intake (and likely fibbed), these men were confined and fed. They were required to walk for 2 miles every day and were prohibited from any other form of exercise. They were under 24-hour supervision. Energy intake and expenditure was meticulously documented. That's control.

Slow, Insidious, and Not Likely to Burden the Healthcare System, at Least in the Beginning

Although the men's thyroid hormone levels changed, they remained within a normal range. These changes would be considered subclinical, and would not necessitate pharmacological action.

A Dab'll Do Ya

Certainly, there's a need to provide adequate selenium. It replenishes the antioxidant enzyme glutathione peroxidase (GP) which is useful in detoxifying acrylamide. You remember acrylamide, don't you? If not, and if you enjoy your bread toasted or your potatoes fried, it might be worth a look, here or here.

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