News Release

Steeped in research: Tea linked to survival after heart attack

Peer-Reviewed Publication

American Heart Association

DALLAS, May 7 – Drinking lots of tea may reduce a person’s risk of dying after a heart attack, according to a report in today’s rapid access issue of Circulation: Journal of the American Heart Association.

In the Determinants of Myocardial Infarction Onset Study, participants who drank the most tea were the least likely to die during the three or four years after a heart attack. The researchers suspect that this may be because tea has flavonoids, antioxidants found naturally in various foods derived from plants. Flavonoids are thought to prevent cardiovascular disease.

“The effects of tea on health have been widely studied, in part because tea contains flavonoids and other antioxidant components, but we don’t know of any previous studies that considered the effect of tea consumption on survival after a heart attack, ” says Kenneth Mukamal, M.D., assistant professor of medicine at Harvard Medical School in Boston. “Flavonoids are probably the best guess for the apparent benefits of tea in this study.”

The findings support those from previous studies that linked flavonoid consumption to a lower risk of coronary heart disease and a lower risk of death in people who have heart or blood vessel disease, says Mukamal, who is also an associate in medicine at Beth Israel Deaconess Medical Center.

Researchers interviewed the 1,900 participants an average of four days after having a heart attack. The participants were asked about their usual consumption of caffeinated tea over the last year. Researchers separated the patients into three groups based on weekly tea consumption: non-drinkers, moderate use (fewer than 14 cups), and heavy use (14 or more cups).

The interviews revealed that 1,019 of the patients drank no tea in the year before their heart attack; 615 were moderate drinkers; and 266 were heavy drinkers. In the moderate-use group, participants drank about two cups per week on average. Those in the heavy-use group drank about 19 cups per week on average.

During an average follow up of 3.8 years, 313 patients died. About 75 percent of the deaths were from cardiovascular disease. After accounting for differences in age, gender, and clinical and lifestyle characteristics, the researchers found an inverse relationship between tea consumption and death.

Moderate tea use was associated with a 28 percent lower death rate compared to the death rate of non-drinkers. People who reported heavy tea consumption had a 44 percent lower death rate during the follow-up period.

“We found that tea drinkers generally had lower death rates regardless of age, gender, smoking status, obesity, hypertension, diabetes or previous heart attack,” Mukamal says.

Caffeine consumption per se did not affect mortality risk after myocardial infarction, he says. The researchers evaluated caffeine intake from sources other than tea and found no association with the risk of dying during follow up.

Several possible mechanisms could explain an association between tea consumption and survival, Mukamal says.

A recent randomized trial found that black tea consumption improved endothelial function (the blood vessels’ ability to relax) in people with coronary heart disease, he says. “Flavonoids also inhibit the oxidation of low-density lipoprotein (LDL). Oxidized LDL may promote atherosclerosis, so this property of tea may help prevent additional heart attacks, at least in some patients.”

In addition, flavonoids could have an anti-clotting effect. Studies have shown that flavonoids kept blood platelets from clumping together in test tubes, but whether this occurs in the body is unclear.

The findings should apply to different types of tea, Mukamal says. Black tea accounts for most tea consumption in North America, as well as the largest portion of flavonoid intake, he says.

Other foods rich in flavonoids include apples, onions and broccoli.

Mukamal says the results are limited because researchers have little information about study participants’ diets, which might influence the risk of dying after a heart attack. Although the findings support the concept that tea consumption reduces the risk of death after heart attack, the association needs to be tested in controlled studies, he adds.

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Co-authors are Malcolm Maclure, Sc.D.; James E. Muller, M.D.; Jane B. Sherwood, R.N.; and Murray A. Mittleman, M.D., Dr.P.H.

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