University of California at Los Angeles researchers think they can explain why coffee consumption protects against the development of type 2 diabetes mellitus.
The researchers found coffee increases plasma levels of a protein called sex hormone-binding globulin or SHBG which regulates the biological activity of the body's sex hormone, testosterone and estrogen.
The protein has been thought for long to play a role in the development of type 2 diabetes mellitus.
Dr. Simin Liu, Professor at the UCLA School of Public Health and the David Geffen School of Medicine at UCLA reported in the journal Diabetes that women who drank more than four cups of coffee a day were more than 50 percent less likely to develop diabetes, compared with those who did not drink coffee.
In the United States, about 20 million men and women suffer from diabetes, 90 to 95 percent is type 2 diabetes.
Earlier studies showed an inverse association between coffee intake and risk for type 2 diabetes and it was assumed that coffee may improve the body's tolerance to blood sugar by increasing metabolism or improving its insulin tolerance.
Earlier, Dr. Liu and colleagues had identified two mutations in the gene coding for SHBG, one increasing the risk of developing type 2 diabetes and the other reducing the risk of the disease depending upon the level of SHBG in the blood.
A large clinical study revealed the important role of sex hormones in the development of type 2 diabetes, and it’s known that SHBG not only regulates the sex hormones, but may also directly mediate the signaling of sex hormones.
"It seems that SHBG in the blood does reflect a genetic susceptibility to developing type 2 diabetes," Dr. Liu said.
"But we now further show that this protein can be influenced by dietary factors such as coffee intake in affecting diabetes risk — the lower the levels of SHBG, the greater the risk beyond any known diabetes risk factors."
For the current study, the researchers identified 359 new diabetes cases matched by age and race with 359 apparently healthy controls selected from among nearly 40,000 women enrolled in the Women's Health Study, which was originally designed to evaluate the benefits and risks of low-dose aspirin and vitamin E in the primary prevention of cardiovascular disease and cancer.
Women who drank four cups of caffeinated coffee each day were found to have higher amounts of SHBG than non-drinkers and were 56 percent less likely to develop diabetes than non-drinkers.
And the coffee consumption also benefits the protective copy of the SHBG gene.
However, after adjustment for blood SHBG levels, the decrease in risk associated with coffee consumption became insignificant, indicating it is SHBG that mediates the decrease in risk of developing type 2 Diabetes, Liu said.
Co-author Goto said consumption of decaffeinated coffee didn't have any association with the SHBG level, nor diabetes risk.
Stephen Lau and editing by Aimee Keenan-Greene
SOURCE: foodconsumer
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