The Health Benefits of Green Tea. Part II
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Heart Benefits:
When hamsters were fed the equivalent in humans of two quarts a day of green and black tea at the University of Scranton, Pennsylvania, they demonstrated reduced blood cholesterol levels and decreased LDL (bad cholesterol) oxidation . Since LDL oxidation leads to plaque which can clog arteries, this means that it provided a protective effect against heart disease in the hamsters.
And in Australia, Dr. Paul Roach and CSIRO discovered that feeding rabbits catechins purified from green tea lowered cholesterol levels. There will need to be further studies in humans to see if this effect also occurs in people as well.
There was a study done with humans on the effect of tea on heart disease by Erasmus University Medical School in Rotterdam. Both green and black tea are rich in flavonoids, the substance in tea speculated to exert a heart protective effect. The Rotterdam study included 3454 men and women aged 55 and older. After doing radiographic studies of the aorta in the tea drinkers, the researchers concluded that tea drinking appears to exert some mild protection against coronary heart disease (clogging of the arteries with plaque).
Case Western Reserve University at Cleveland completed a study with mice that indicated that taking in the equivalent of four or more cups of green tea a day helped to prevent or lessened the severity of collagen-induced arthritis in the mice (which is similar to rheumatoid arthritis in humans). This has led to speculation that green tea might help humans with arthritis, although further clinical studies with humans will need to be done to see if this is true. (Are you noticing a trend? Most of the studies with green tea up to date have been done with test tubes or animals, and until there is reliable double blind testing with human subjects, conclusions on human health can’t and shouldn’t be made).
The American Journal of Clinical Nutrition published the results in 1999 of a study done at the University of Geneva in Switzerland by Dr. Abdullo on the effects of green tea and dieting. The study consisted of two groups: one of men who took a combination of caffeine (50mg.) and a placebo (dummy pill) while the other took a combination of caffeine and green tea extract. The group that took the green tea extract with caffeine burned four percent more calories per day than the placebo group. And this effect was not from the extra caffeine in green tea, since they calculated that factor into the placebo group’s results.
And It May Prevent Tooth Decay
The University of Illinois at Chicago College of Dentistry found in research funded by the Tea Trade Health Research Foundation that subjects that rinsed with black tea for one minute ten times a day had lower plaque levels on their teeth (but there was no comparison with controls rinsing with water vigorously for one minute ten times a day, which raises the question of whether the polyphenols in tea inhibit bacterial growth, or whether regular, prolonged mouth rinsing does.
Green tea also contains a natural form of fluoride, which may protect teeth against cavities.
Don’t Overdo It
All teas contain caffeine, which means that over-consumption can lead to insomnia, nervousness and irregular heart beat (which is why nursing mothers and people with heart conditions are advised to limit their consumption). But tea contains less caffeine than coffee or most soda drinks, with only about 40 to 50 mg. of caffeine in 8 ounces of tea compared with about 100 mg. in 8 ounces of coffee.
Also, the flavonoids in tea can partially reduce the body’s absorption of iron from plant sources, although the absorption of iron from animal sources such as meat is not affected.
Conclusions? Study results are still coming in. Some of the more exciting ones involve test tube and animal studies, and it will take time before testing on humans in clinical trials will show whether green tea can prevent cancer or heart disease. But green tea has less caffeine than soda or coffee, contains polyphenols and flavonoids, and when consumed in moderation is a tasty, and very possibly healthful drink.