A grapefruit a day just might keep the doctor away. New findings reported in the May 30, 2012 online edition of PPAR Research add to a growing body of evidence that suggests that a flavonoid in grapefruit called naringenin can lower cholesterol levels, regulate insulin and blood sugar levels, fight abdominal obesity, and reduce hardening of the arteries by activating a family of special nuclear receptors in the liver.

Flavonoids can be found in a variety of foods, including chocolate, green tea and citrus fruits. Studies, including a July 2008 meta-analysis of 133 clinical trials that appeared in the American Journal of Clinical Nutrition, have found that people consuming the largest amount of flavonoid-rich foods have the lowest number of risk factors of heart disease such as hypertension, high cholesterol levels and weight gain. 

In this new study, Canadian researchers at the Robarts Research Institute showed that naringenin may be especially beneficial because it “turns on” nuclear receptors, technically known as peroxisome proliferator-activated receptors (PPARa), in much the same way that fasting and exercise do. This helps prevent the overproduction of cholesterol and triglycerides, guards against the oxidative stress that contributes to a variety of diseases, helps normalize blood sugar and enhances insulin sensitivity. 

While the researchers cite a December 2003 study in Clinical Nutrition showing that taking naringenin reduced LDL (bad) cholesterol by 17 percent and triglycerides by 14 percent, grapefruit may not be for everyone. 

The tart fruit and its flavonoids can interact with a number of medications, including statin drugs like Lipitor or Zocor, calcium channel blockers, some antihistamines, anti-anxiety drugs like Valium or Xanax, some immunosuppressive drugs and antiviral medications used to treat HIV/AIDS. If you take any of these medications, be sure to talk to your health care provider before routinely adding grapefruit or grapefruit juice to your diet or before you take a supplement containing naringenin.