High Selenium Leads to Weight Gain
Chemist Wayne Chris Hawkes prepares to test a rice sample from
China for selenium content.
Meals rich in selenium may slow the rate at which your body burns calories,
ARS researchers report.
This preliminary result is based on a 4-month study of 11 healthy men. It
suggests a possible benefit to patients with wasting syndromes such as those
sometimes associated with AIDS and cancer. Experimental high-selenium therapies
already proposed for these patients might additionally help them stop losing
weightand perhaps even gain.
Chemists Wayne Chris Hawkes and Nancy L. Keim did their selenium study at
the ARS Western Human Nutrition Research Center in San Francisco. Their
volunteers were age 20 to 45.
The five volunteers who ate foods high in selenium received about five times
the Recommended Dietary Allowance, or RDA, of this mineral. These men gained
about a pound and a half, despite the researchers efforts to keep
everyone's weight stable.
The scientists attribute the weight gain to lowered levels of one of the
body's thyroid hormones, known as T3, or triiodothyronine. Levels of another
thyroid hormone, T4, didn't change. The thyroid, through hormones, handles a
wide array of tasks. Among them: regulating your calorie-burning rate.
The six volunteers who ate foods that provided only about one-fifth of the
selenium RDA increased their levels of T3the hormone that is more active
than T4and boosted their fat-burning rates. They lost about 1 pound. That
amount "isn't significant for dieters," Hawkes says, "but
signals the body's response to a low-selenium regimen."
The change in the T3 hormone, revealed in blood tests, was unexpected, says
Hawkes, because it contradicts results from animal studies done elsewhere. Mice
and rats fed low doses of selenium had less T3 and more T4. Animals and humans
use selenium to convert T4 into T3.
Instead of an unappetizing liquid formula spiked with selenium, the San
Francisco study offered familiar foods. Volunteers ate rice from China that was
harvested from regions where the soil is either rich or poor in selenium. Beef
from selenium-rich South Dakota went into the high-selenium menus; low-selenium
beef from selenium-deficient New Zealand was served to volunteers on the
Menus included hot rice sweetened with maple syrup or marmalade for
breakfast; spaghetti with meat sauce, or beef with curried rice, tomatoes,
green peppers, and onions for lunch; and beef and noodle casserole or beef and
rice with teriyaki sauce at dinner.
Besides meats and grains from regions where soils contain ample selenium,
seafoods are also a good source of the mineral. And dairy products and
vegetables provide some of this essential nutrient, too.
In addition to its interaction with thyroid hormones, selenium is a powerful
antioxidant that protects cells from peroxides, an oxidation byproduct.
Selenium deficiency is rare in the United States, except for patients who
are fed intravenously for a long time. Selenium toxicity, too, is uncommon.
''However," cautions Hawkes, "selenium can be poisonous at only 10
times the RDA, so people shouldn't haphazardly gobble selenium
Hawkes plans to conduct a lengthier study to see if the same
selenium-induced changes to thyroid hormones occurand, if they do, how
long they persist. By Marcia Wood, ARS.
Chris Hawkes is in the USDA-ARS
Human Nutrition Research Center, One Shields Avenue, University of
California, Davis, CA 95616; phone (530) 752-5276, fax (530) 752-5271.
Keim is in the USDA-ARS
Human Nutrition Research Center, University of California; phone (530)
752-4163, fax (530) 752-5271.
"High Selenium Leads to Weight Gain" was
published in the October
1995 issue of Agricultural Research magazine.