Coffee is the ultimate health drink, right? After all, a regular java habit is linked with protection against heart disease and more. But that doesn’t mean it’s healthy for you. It even might be dangerous.

The caffeine gene: When it comes to caffeine, about 15% of people are slow metabolizers due to a variant of the gene CYP1A2. They’re more sensitive to the effects of caffeine, and it lingers much longer in their bodies.

Result: A much higher risk of developing high blood pressure and heart disease. In research published in JAMA, coffee was linked to heart attacks—but only in people with this gene variant. Another study found that moderate coffee drinkers who were slow caffeine metabolizers were 72% more likely to develop high blood pressure.

Insomnia and anxiety: Caffeine affects people differently when it comes to sleep and anxiety, too. Consider sleep. The average person clears half the caffeine from his/her body in about four to six hours—but it can take up to 24 hours for slow metabolizers! As for anxiety, people with panic disorder and ­social phobia are more sensitive to caffeine than people without these disorders.

Commonsense test: Want to know if you have the slow-metabolizing CYP1A2 variant? If you sign up for the gene-­typing service 23andMe.com (about $200), you get this information in the “wellness report.” Or you could simply monitor your systolic blood pressure to see if it goes up five points or more after drinking a cup. If so, cut back.

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