Vitamin A Suppresses Type 1 Diabetes in Animal
Study
December 28, 2007
Pumpkin pie, sweet potatoes and many other holiday favorites are rich
in vitamin A, a nutrient essential for good health. Now a study by Agricultural
Research Service (ARS) nutrition
scientists has shown, for the first time, that high levels of vitamin A can
suppress development of type 1 diabetes in laboratory mice prone to that
disease.
Type 1 diabetes, which affects more than 750,000 Americans, occurs
when the immune system mistakenly attacks and destroys the pancreas'
insulin-producing beta cells. Scientists already know that vitamin A and
antioxidants —such as those in the freeze-dried grape powder also tested in
the study—can regulate the immune system.
However, apparently no one had shown the suppressive effect of either
vitamin A or grape powder on type 1 diabetes in either lab mice or humans,
according to ARS physiologist
Charles
B. Stephensen.
He collaborated with molecular biologist Susan J. Zunino for the
investigation, conducted in their laboratories at the ARS
Western
Human Nutrition Research Center in Davis, Calif. They reported their
findings earlier this year in the Journal
of Nutrition.
Blood sugar levels of the 45 mice in the experiment were taken
regularly to determine onset of diabetes. At about seven months, only 25
percent of those mice eating a high-vitamin-A feed, and 33 percent of those
eating grape-powder-enriched feed, had developed type 1 diabetes, while 71
percent of those on non-enriched feed had became diabetic.
Differences in levels of a protein called tumor necrosis factor-alpha,
or TNF-alpha, linked in other studies to type 1 diabetes, were notable.
TNF-alpha production by immune cells of mice fed the vitamin A- or
grape-powder-enriched feed was significantly lower than that in cells of mice
fed standard feed.
The study is part of ongoing research at the nutrition center to
discover more about the potential of vitamin A and other nutrients to help
prevent diabetes, cancer, asthma and other diseases of the immune system.
ARS, the U.S. Department of
Agriculture's chief scientific research agency, and the
National Institutes of Health of the
U.S. Department of Health and Human Services
funded the research.
Source: U.S. Department of
Agriculture, ARS.
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