Vitamin A Suppresses Type 1 Diabetes in Animal
By Marcia Wood
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 antioxidantssuch
as those in the freeze-dried grape powder also tested in the studycan
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
He collaborated with molecular biologist Susan J. Zunino for the
investigation, conducted in their laboratories at the ARS
Human Nutrition Research Center in Davis, Calif. They reported their
findings earlier this year in the Journal
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.