Grapefruit has long had a reputation as a health food. Not only is it loaded with nutrients like vitamin C, potassium and folic acid, but it also has been reported to help people lose weight.
For decades, dieters were convinced that grapefruit had special fat-burning power. This idea was bolstered by advertisements like one for a diet plan in which a muscular construction worker pulled a grapefruit out of his lunchbox with disdain, squeezed it and tossed it away. Then he held up a little grapefruit pill and sang the praises of its grapefruit essence for weight loss.
One popular grapefruit diet has people eating either half a grapefruit or drinking 8 ounces of grapefruit juice three or four times daily.
We haven't seen any studies showing that eating grapefruit will actually make anyone thinner, but new research does demonstrate that grapefruit can help lower cholesterol.
Scientists divided 57 volunteers into three groups of 19 people each. All the subjects had undergone coronary bypass surgery, and all had high cholesterol and triglycerides.
One group got a red grapefruit each day with meals for a month; a second group got a white grapefruit. The control group got no grapefruit.
At the end of the month, those who had eaten red grapefruit had total cholesterol levels 15 percent lower. The group that had eaten white grapefruit had lowered their cholesterol by about half that much. Dangerous LDL cholesterol had also dropped, by 20 percent and 10 percent respectively, and triglycerides were lower as well (Journal of Agricultural and Food Chemistry, March 22, 2006).
Although grapefruit has ample dietary fiber, the scientists suspect that some other component of the fruit might be responsible for this fascinating effect.
But before anyone adopts a grapefruit approach to cholesterol control, beware of drug interactions. Back in 1989, Canadian researchers discovered, almost by accident, that grapefruit juice significantly increased levels of the blood pressure medicine felodipine (Plendil). At first, this finding seemed like a curiosity. One person who read about grapefruit interactions in this column was laughed out of the pharmacy when he asked about it.
No one is laughing anymore. Grapefruit can interact with dozens of drugs, including some very popular cholesterol-lowering medications (Lipitor, Mevacor and Zocor). Because of biological variability, the effects differ from one person to another and even from one batch of grapefruit juice to another (Journal of Agricultural and Food Chemistry, Jan. 11, 2006). But in some cases, drinking grapefruit juice raises levels of drugs in the blood and increases the risk of side effects. Dozens of drugs such as BuSpar (buspirone), Cordarone (amiodarone), Tegretol (carbamazepine) and Viagra (sildenafil) may be affected.
To learn more about this important issue, we offer our Guide to Grapefruit Interactions. Anyone who would like a copy, please send $2 in check or money order with a long (No. 10), stamped, self-addressed envelope to: Graedons' People's Pharmacy, No. J-91, P.O. Box 52027, Durham, NC 27717-2027. It can also be downloaded for $2 from our Web site: www.peoplespharmacy.com.
Joe Graedon is a pharmacologist. Teresa Graedon holds a doctorate in medical anthropology and is a nutrition expert. Their syndicated radio show can be heard on public radio. In their column, Joe and Teresa Graedon answer letters from readers. Write to them in care of this newspaper or e-mail them via their Web site: www.PeoplesPharmacy.com.