Coffee is one of the most popular drinks in the world, and many people enjoy it every day.
For most healthy adults, moderate coffee drinking has been linked to several possible benefits, including better alertness and a lower risk of some long-term diseases.
However, a large study suggests that heavy coffee drinking may be unsafe for people whose blood pressure is already extremely high.
The research found that people with severe high blood pressure who drank two or more cups of coffee a day had about twice the risk of dying from heart or blood vessel disease compared with those who did not drink coffee.
Severe high blood pressure was defined as a reading of at least 160/100 mm Hg. The same increase in risk was not seen in people with lower blood pressure.
The study included more than 18,600 adults in Japan who were between 40 and 79 years old. Researchers recorded their blood pressure, coffee habits, green tea intake, and other health details, then followed them for many years.
The findings were published in the Journal of the American Heart Association.
Coffee contains caffeine, which can briefly raise blood pressure and make the heart beat faster. It may also cause nervousness, poor sleep, or a feeling that the heart is racing, especially when large amounts are consumed. These effects may place extra pressure on the heart and blood vessels of someone whose blood pressure is already dangerously high.
The results do not mean that coffee is harmful to everyone. In the study, drinking one cup a day was not linked to a greater risk of death from heart disease, even among people with very high blood pressure. Earlier research has also suggested that moderate coffee drinking may offer some protection against heart attacks and strokes in otherwise healthy people.
The researchers also examined green tea because it contains caffeine. Unlike heavy coffee drinking, regular green tea consumption was not linked to a higher risk of heart-related death at any blood pressure level. One possible reason is that green tea contains plant compounds called polyphenols, which may help reduce inflammation and protect blood vessels.
Still, this type of study cannot prove that coffee directly caused the deaths. Coffee drinkers may differ from non-coffee drinkers in other ways that affect their health, and cup sizes and coffee strength can vary. More studies are needed to understand why the risk appeared only among people with severe high blood pressure.
Anyone with high blood pressure should continue checking it regularly and take prescribed medicines exactly as directed. A diet rich in vegetables, fruit, whole grains, and lean protein can help, while reducing salt, smoking, and heavy alcohol use can lower strain on the heart. Regular activity, enough sleep, and stress management are also important parts of treatment.
People with readings of 160/100 mm Hg or higher should discuss their caffeine intake with a doctor. It may be sensible to reduce coffee, choose decaffeinated drinks, or try lower-caffeine options such as green tea, depending on individual health needs. Coffee should not be stopped or restricted because of one study alone, but very high blood pressure is a strong reason to be cautious.
The main message is that the health effects of coffee may depend on the person drinking it.
A habit that is harmless or beneficial for one person may create added risk for someone with serious hypertension. Small changes in daily caffeine intake, combined with proper medical care, could help protect the heart over the long term.
If you care about nutrition, please read studies that vitamin D can help reduce inflammation, and vitamin K may lower your heart disease risk by a third.
For more health information, please see recent studies about foods that could sharp your brain, and results showing cooking food in this way may raise your risk of blindness.
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