A new study has found that drinking two or more cups of coffee a day may double the risk of death from heart disease in people with very high blood pressure. The research, led by Hiroyasu Iso and published in the Journal of the American Heart Association, looked at how coffee and green tea affect people with different blood pressure levels.
High blood pressure, also called hypertension, is a major risk factor for heart attacks and strokes. In this study, researchers followed over 18,000 adults in Japan, aged 40 to 79, for nearly 19 years.
They divided the participants’ blood pressure into five groups: normal (under 130/85), high-normal, mild hypertension (140–159/90–99), and severe hypertension (160/100 or higher). The last two groups—grade 2 and grade 3—were considered to have severe high blood pressure.
The team found that among people with severe high blood pressure, those who drank two or more cups of coffee each day had twice the risk of dying from heart-related causes compared to those who didn’t drink coffee at all. However, this increased risk was not seen in people with lower blood pressure levels.
Interestingly, drinking one cup of coffee a day did not raise the risk of death from heart disease for people in any blood pressure category. And drinking green tea—no matter how much—was not linked to increased risk of heart-related death at all.
Both coffee and green tea contain caffeine. According to the U.S. Food and Drug Administration (FDA), a cup of coffee usually contains 80 to 100 milligrams of caffeine, while a cup of tea contains only 30 to 50 milligrams.
So caffeine levels may be one reason why coffee has a stronger impact on the heart, especially in people who already have serious blood pressure problems.
Previous studies have shown that moderate coffee intake may have health benefits, such as lowering the risk of chronic illnesses, boosting alertness, and even helping survivors of heart attacks live longer.
However, too much coffee can also raise blood pressure, increase anxiety, cause heart palpitations, and make it harder to sleep. For people with already high blood pressure, these effects may become dangerous.
Researchers believe that people with severe hypertension are more sensitive to caffeine. In these cases, caffeine’s negative effects on blood pressure and heart rhythm may outweigh its possible benefits. That’s why the researchers suggest that people with very high blood pressure should limit or avoid drinking too much coffee.
As for green tea, it may offer some protective effects. It contains compounds called polyphenols, which are known for their antioxidant and anti-inflammatory properties. These nutrients may help protect the heart without the risks that come with high caffeine intake.
In short, while coffee can be part of a healthy diet for many people, those with severe high blood pressure should be cautious. One cup a day appears safe, but drinking two or more could be harmful for people with dangerously high blood pressure. Green tea, on the other hand, seems to be a safer choice.
If you care about coffee, please read studies that drinking coffee this way can help prevent stroke, heart disease, and drink coffee after breakfast, not before, for better blood sugar control.
For more information about nutrition, please see recent studies about natural supplement that could relieve anxiety, and results showing this common food oil in the U.S. can change genes in the brain.
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