Aedin Cassidy at the University of East Anglia in England and colleagues at Harvard School of Medicine analyzed data on the risk of stroke in almost 70,000 U.S. nurses. They looked at what the nurses ate, especially forms of flavonoids, found in plants.
"Citrus flavonoids, called flavanones, seemed to be associated with a reduction in risk," Cassidy said in a statement. "Our data suggest that if you eat more citrus fruit, it may modestly reduce your risk of stroke."
Cassidy said more research is needed and people should check with their doctor if they are taking any medications.
The Harvard Medical School Health Guide warned grapefruit and grapefruit juice are healthful, providing vitamin C, potassium, dietary fiber and other nutrients, but can also interact with dozens of medications.
"Doctors are not sure which of the hundreds of chemicals in grapefruit are responsible, but the leading candidate is furanocoumarin. It is also found in Seville (sour) oranges and tangelos; although these fruits have not been studied in detail, the guidelines for grapefruit should apply to them as well," the guide said. "Grapefruit's culprit chemical does not interact directly with medications, it binds to an enzyme in the intestinal tract known as CYP3A4, which reduces the absorption of certain medications."
A variety of medications can be boosted by grapefruit, including calcium channel blockers for high blood pressure, angina; statins for high cholesterol; immunosuppressants to prevent rejection of transplanted organs; and benzodiazepines for anxiety and insomnia, the guide said.