Harvard Heart Letter

Heart Beat: Coffee may slow the flow

Heart Beat

Coffee may slow the flow

A jolt of java before exercise limits the body's ability to increase blood flow through coronary arteries when the heart needs an extra supply of oxygen and fuel. The change isn't huge. Two cups of coffee drunk an hour before exercise reduced the exercise-induced increase in blood flow by 22%, report Swiss researchers in the Jan. 17, 2006, Journal of the American College of Cardiology.

For someone with a healthy heart, this wouldn't be noticeable. It could pose problems, though, for individuals with cholesterol-narrowed arteries or those whose arteries don't relax and open as they should when the heart needs to work harder. The effect is even greater at high altitudes.

If you like to drink coffee before you exercise, just to be on the safe side, quaff it at least an hour before working out.

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