Studies Find Health Benefits From Tea

A dozen or so studies reported at the American Chemical Society meeting show health benefits from tea that range from fighting fat to fighting cancer.

In what seems to be the first study linking immunity with tea, researchers in Boston found people who drank five to six cups of black tea each day seemed to get a boost in that part of the immune system that acts as a first line of defense against infection.

"We found that certain molecules were shared by bacteria, parasites, and vegetables - and one of the vegetables was tea," says study author Dr. Jack F. Bukowski, an assistant professor of medicine at Harvard Medical School and staff rheumatologist at Brigham and Women's Hospital.

"These molecules could activate a certain component of the immune system called gamma delta T lymphocytes, which are very important as the first line of defense against infection and tumors," he says.

"Vitamin for the Immune System"

Dr. Bukowski and his colleagues asked non-tea drinking, non-coffee drinking volunteers to consume five to six cups of black tea infusion or instant coffee for either two or four weeks.

They then took blood samples and tested the activity of the immune system against bacteria.

"We found that samples taken after they drank tea were able to react against the bacteria fivefold better by making a very important protein called interferon gamma," Dr. Bukowski says.

"If you put two and two together, that should mean you're going to be more able to fight off diseases because that's a very important bacteria-fighting and virus- and tumor-fighting molecule, but we did not go on to show that drinking tea actually protects you against getting sick," he says. That will be the subject of the next study.

Although the tea cannot be viewed as a cure, it could be viewed "almost as a vitamin for the immune system," Dr. Bukowski says. And more of these "vitamins" will probably be found in vegetables, Dr. Bukowski adds, which means you should probably have some vegetables with your tea.

Lab Studies Look at Anti-Cancer Qualities

A second study found that mice who had been genetically engineered to develop prostate cancer, and who drank the equivalent of about six cups of tea a day, did not end up developing tumors.

"Those animals who drank tea were substantially protected and they lived longer," says study author Dr. Hasan Mukhtar, a professor of cancer research at the University of Wisconsin in Madison.

No one knows if the same mechanism will be at play in humans, but Dr. Mukhtar says he suspects that tea will have some effect in some patients.

"China has the lowest prostate cancer rate in the world and Japan is also very low, and they drink much more tea," he notes.

Another study found that a green tea extract reduced body fat in mice, possibly by inhibiting the absorption of fats and starches, and that drinking green tea may mitigate DNA damage from smokers that could lead to mouth cancer.

Still other researchers are working on developing a cream made up of tea polyphenols which would ward off skin cancer.

Finally, researchers at the American Chemical Society meeting found that drinking tea improved the function of blood vessels and platelets, and may therefore reduce the risk of heart attack and stroke.

Always consult your physician for more information.

Online Resources

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American Academy of Allergy, Asthma and Immunology

American Cancer Society

American Lung Association

Centers for Disease Control and Prevention (CDC)

National Heart, Lung, and Blood Institute (NHLBI)

National Institutes of Health (NIH)

National Women's Health Information Center

US Department of Heath and Human Services

October 2003

Studies Find Health Benefits From Tea

"Vitamin for the Immune System"

Lab Studies Look at Anti-Cancer Qualities

People with Asthma Cautioned about Melatonin

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People with Asthma Cautioned about Melatonin 

Melatonin, a naturally occurring hormone that helps regulate the body's circadian rhythms, may make asthma worse at night, a new study finds.

"We found that patients who have nocturnal asthma have higher melatonin levels than patients who do not have asthma," says study author Dr. Rand Sutherland, at the National Jewish Medical and Research Center in Denver.

"Higher levels of melatonin were associated with a greater worsening of lung function overnight," Dr. Sutherland says, following his report in the Journal of Allergy and Clinical Immunology.

Melatonin is produced by the pineal gland in the brain, and many people take supplemental melatonin to help them sleep and to combat jet lag.

In the study, Dr. Sutherland and his colleagues recruited seven patients with nocturnal asthma, 13 patients with non-nocturnal asthma, and 11 patients without asthma. While the patients slept, the researchers took blood samples every two hours.

Dr. Sutherland's team also measured lung function before the patients went to bed and again after they woke up.

Results showed the patients with nocturnal asthma had the highest levels of melatonin and the biggest drop in lung function.

In addition, among patients with nocturnal asthma, lung function dropped an average of 19 percent compared with 5 percent in patients with non-nocturnal asthma. Among non-asthmatic patients, lung function increased about 2 percent.

In other experiments, melatonin has been shown to rev up inflammatory cells and make them produce cytokines, which are inflammatory markers, Dr. Sutherland notes.

"These findings raise concern that high melatonin levels may play a role in making asthma worse at night, and therefore people with asthma should avoid taking supplemental melatonin," Dr. Sutherland advises.

Dr. Charles Irvin, director of the Vermont Lung Center at the University of Vermont, says this study is the first real attempt to find out the cause of nocturnal asthma.

"The conclusion by Sutherland that patients with asthma should be cautious about using melatonin is just right," Dr. Irvin says.

Patients want to find non-pharmaceutical treatments, Dr. Irvin says, but many of the alternatives may have active substances that may be harmful. Many like melatonin are very powerful, he adds, and people need to be careful about how they use these supplements.

"Patients with mild asthma may try melatonin, but if their asthma gets worse, they should stop it right away," Dr. Irvin says. "However, people with nocturnal asthma should avoid taking melatonin altogether."

Always consult your physician for more information.