July, 2005, Vol. 06, Issue 07
Green and Black Tea May Fight Cataracts Caused by Diabetes
In the JAFC study, meanwhile, researchers from the University of Scranton in Pennsylvania monitored the effects of green tea 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.
The teas were included in the rats' drinking water at a solution of 1.25 percent, which was equivalent to a human drinking 4.6 eight-ounce cups of tea per day.
The teas were fed to the rats every day for three months, at which time they were killed. 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.
According to the scientists, the teas "significantly decreased glucose, and ... also inhibited the pathological pathways of diabetes in lens, plasma, and red blood cells." On average, plasma glucose levels in the diabetic rats drinking tea were reduced between 28 percent and 32 percent, which corresponded favorably to a 2003 study of oolong tea in people with type 2 diabetes.4 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 (out of four). In diabetic rats given green tea, the average cataract rating was 2.61; in diabetic rats taking black tea, the average rating was 2.24.
"This paper is the first study to examine three mechanisms of diabetic pathology and show a relationship to a diabetic complication, cataracts," the authors wrote in their conclusion. "Both green and black teas appear to be of equal efficacy for improving the diabetic state by means of a hypoglycemic effect, which in turn inhibits the biochemical indicators of diabetic pathology."