It looks harmless, even virtuous – that pink, tangy wedge at breakfast. But grapefruit contains compounds that interfere with enzymes in the gut and liver, the very enzymes that normally break down medicines. Block those, and suddenly the drug lingers longer in the bloodstream, building up to levels higher than the doctor prescribed. Cholesterol-lowering statins, blood pressure tablets, even certain anti-allergy pills are on that list. The solution is simple: try oranges, lemons, or sweet lime instead – all the citrus taste, without the trouble.