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Save Your Eyes With Green and Black Tea

Herbalists have long recommended tea to help treat myriad conditions, including indigestion, high cholesterol and weight gain. Now, new study results show that green and black tea may inhibit the development of diabetes-related cataracts.

Researchers monitored the effects of green and black tea in four groups of rats: a normal (non-diabetic) group; a diabetic control group; a group of diabetic rats given green tea; and a diabetic group given black tea.

Over a three-month period, the teas were included in the rats' drinking water, equivalent to a human drinking 4.6 eight-ounce cups of tea per day. The chemical composition of the rats' blood and eye lenses was then analyzed to determine whether the teas lowered blood glucose levels and reduced the incidence of cataracts, a common side-effect associated with diabetes.

Results: The teas "significantly decreased glucose, and ... inhibited the pathological pathways of diabetes in lens, plasma, and red blood cells," the researchers noted. On average, plasma glucose levels in the diabetic rats drinking tea were reduced between 28% and 32%. In addition, tea consumption appeared to reduce the severity of cataracts. Rats in the diabetic control group had an average cataract rating of 3.02 (0-4 scale; 0 = normal vision; 4 = nuclear opacity beginning). In diabetic rats given green tea, the average cataract rating was only 2.61; in diabetic rats taking black tea, the average rating was only 2.24.

Although the authors suggest the need for further studies to determine the role of teas in the prevention or treatment of diabetes in humans, the results of this study are clear: in addition to having other benefits, green and black may help prevent diabetes-related cataracts, as well. For more information on nutrition and herbs, visit


Vinson JA, Zhang J. Black and green teas equally inhibit diabetic cataracts in a streptozotocin-induced rat model of diabetes. Journal of Agricultural and Food Chemistry 2005;53:3710-3713.


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