Black Tea Inhibits Diabetes
Everybody knows green tea is healthier than black tea. Right? Well, not so fast! Though green tea has received much acclaim because of its superstar antioxidant content, black tea, it turns out, does more to lower blood sugar. Black tea contains a polysaccharide that works very much the way pharmaceutical diabetes drugs work, according to a new study out of Tianjin University in China.
It's been known for some time that tea offers benefits to diabetics, but previous research hasn't compared the various kinds of tea to see which works best. This study compared the effects of green tea, black tea, and oolong. Although all three types of tea come from the same type of plant -- camellia sinensis -- they get processed differently, and it is the processing that creates differences in flavor and composition. Black tea undergoes the most processing and is fully fermented; green tea, which is unfermented, undergoes the least, and oolong tea fits right into the middle.
The natural assumption is that less processing is better, and in fact, green tea does preserve its antioxidant content better, plus has less caffeine. It's the catechins in green tea that confer all those health benefits, and in processing, those catechins convert into other compounds. Still, according to Dr. John Weisburger of the Institute for Cancer Prevention, "Whether it's green or black, tea has about eight to 10 times the [antioxidants] found in fruits and vegetables."
Plus, a closer look at what happens to the catechins in the process of making black tea reveals that they simply convert into other antioxidants -- theaflavins and thearubigens, which, although probably not as powerful as catechins, do confer health benefits that just now are starting to be investigated. Studies have shown that in addition to lowering blood sugar, black tea has antiviral properties, anticancer properties, and it improves cardiovascular function to a remarkable degree.
But the research on the blood-sugar lowering properties of tea focused not on the catechin content, but on the polysaccharide content in the tea. It seems that processing tea reduces the molecular weight of the polysaccharides, and according to head researcher Haixia Chen, those lighter-weight polysaccharides actually work better to block an enzyme called alpha-glucosidase, which converts starch into glucose. This is exactly what the mainstay diabetes drugs Precose and Glyset do. Plus, black-tea polysaccharides showed the best ability to scavenge disease-causing free radicals. In other words, the polysaccharides in black tea have far more powerful antioxidant properties than the polysaccharides in other teas. The game is still on.
Black tea already has been used in diabetes treatment in China and Japan because of its ability to reduce blood sugar, but this research takes it one step further by demonstrating that black tea actually stops the blood sugar spike triggered by eating. Dr. Chen says, "Many efforts have been made to search for effective glucose inhibitors from natural materials. There is a potential for exploitation of black tea polysaccharide in managing diabetes."
The researchers say they don't know if simply drinking black tea will do the trick. They used black tea extract derived by chemically processing the tea leaves. Certainly, drinking organic tea minus the chemicals has far more appeal from the standpoint of both pleasure and cost, to say nothing about consuming chemical residue, but there's a potential goldmine in selling tea extract that might influence what consumers get told. Given that in the US alone, eight percent of the population already has diabetes and that percentage keeps increasing, the pharmaceutical companies may be poised to elbow out the tea companies and exploit a fortune in prescription Earl Gray. Already, US consumers pay $116 billion annually for diabetes medication, much of which could be converted to tea medication. (If you want to partake in the profits and you live in warm, wet climes, this might be a good time to plant some camellia sinensis -- seriously.)
It also might be a good time to start drinking it, because in spite of what the researchers say, previous studies have shown that merely drinking tea does work. A study a few months ago, for instance, found that drinking three cups of black tea daily cut stroke risk by 21 percent. Another study last year found that both green tea and black tea reduced blood sugar as well as the incidence of diabetic cataracts in rats. The researchers concluded that average-weight adults could get the same effect by drinking 4.5 cups of tea daily.
One note before you start taking tea breaks every few hours: drink your tea without milk of any sort, including soy milk, as some studies indicate that milk blocks the action of the beneficial compounds in tea (1, 2, 3). Although the studies are conflicting, it's probably best to err on the side of caution. And by the way, if you don't enjoy tea, studies show that drinking six cups of coffee daily cuts diabetes risk by 50 percent for men and 30 percent for women. Of course, imbibing six or more cups of coffee daily simultaneously ups the risk of bouncing off the walls, annoying your spouse, and setting off hypertension, kidney stones, osteoporosis, and so on. You'll probably stay safer and more civilized drinking 4.5 cups of tea.
Or, you can just look for a black tea extract in your neighborhood health food store.