Green tea may lower heart disease risk

Harvard Heart Letter

Here's what studies have revealed about this popular beverage.

Lowering your risk of cardiovascular disease may be as easy as drinking green tea. Studies suggest this light, aromatic tea may lower LDL cholesterol and triglycerides, which may be responsible for the tea's association with reduced risk of death from heart disease and stroke.

What the evidence shows

A number of studies have looked at possible links between green tea and cardiovascular disease.

A study of 40,530 Japanese adults found that participants who drank more than five cups of green tea a day had a 26% lower risk of death from heart attack or stroke and a 16% lower risk of death from all causes than people who drank less than one cup of green tea a day.

Last year, a meta-analysis of observational studies—13 conducted in green tea drinkers and five in black tea drinkers—found that people who drank the most green tea had a 28% lower risk of coronary artery disease than those who drank the least green tea. Black tea had no effect on heart risk.

Another 2011 meta-analysis of 14 randomized, placebo-controlled clinical trials found that green tea significantly lowered LDL cholesterol and triglyceride levels. Many of the studies had been conducted with capsules containing catechins, the active polyphenols in green tea, rather than with the beverage itself.

The bottom line

"The limited data available on green tea support a potential association between green tea and beneficial properties in relationship to risk factors for cardiovascular disease," says Kathy McManus, director of the department of nutrition at Brigham and Women's Hospital.

Although no serious side effects were reported in the studies, catechins have been reported to raise liver enzymes in animals. Green tea is also a major source of oxalate, which can cause kidney stones. This suggests that drinking more than five cups of green tea a day (or taking the equivalent in catechin capsules) might have more risks than benefits. When consumed wisely, though, green tea may improve your cardiovascular health.

"The bottom line is that no serious red flags were seen in the amount of tea they were testing. It appears that a few cups a day may be beneficial," says McManus.