What it is
Consumers will find three types of grapefruit-based supplements on natural products store shelves: a concentrate from the whole grapefruit that uses the entire fruit, including the skin and rind; an extract that contains only concentrated grapefruit rind; and an extract taken from the seed. Each offers distinct benefits. The whole grapefruit extract may encourage weight loss. The grapefruit rind extract provides pectin, a type of soluble fiber that helps manage cholesterol levels. And the grapefruit seed extract may help control symptoms of irritable bowel syndrome (IBS).
How it works
Researchers suspect whole grapefruit extract helps people shed extra pounds by decreasing levels of insulin, a hormone that regulates fat metabolism. And yes, there is proof that it works. In a recently completed 2004 clinical trial involving 100 overweight men and women at the Scripps Clinic, a research-driven care facility in San Diego, researchers found that simply eating half a grapefruit three times daily or taking one 500 mg capsule of whole grapefruit extract three times per day resulted in a loss of approximately 3 pounds per person during a three-month period, compared with a placebo group whose members did not include grapefruit in any form in their diets. The weight loss occurred without any other diet or exercise changes.
Grapefruit rind or pectin supplements have been shown to help significantly lower cholesterol by blocking cholesterol absorption, as well as by binding to and promoting the excretion of cholesterol (Clinical Cardiology, 1988, vol. 11, no. 9).
And grapefruit seed extract has been shown to provide some relief from IBS symptoms, such as intermittent diarrhea, constipation, bloating, and abdominal discomfort. Its touted benefit for immune function, though, is weak at best. Grapefruit seed extract has also been promoted as a germ-killer, but researchers now believe that these germ-killing abilities are actually linked to synthetic preservatives in the liquid extracts and not the grapefruit seed itself (Pharmazie, 1999, vol. 54, no. 6).
The whole grapefruit extract and pectin extract from grapefruit rind are available in capsules or powders. The grapefruit seed extract is available in capsule and liquid concentrate forms.
Whole grapefruit extract: Each 500 mg capsule is equivalent to one-half of a fresh grapefruit. For weight loss purposes, the recommended dose is three 500 mg capsules per day. Grapefruit pectin: Take 1–3 grams of pectin daily. Grapefruit seed extract: Take 10–15 drops of the liquid concentration in water three times daily. The standard dose of seed extract capsules supplies 100–200 mg each, also generally taken three times daily.
Whole grapefruit extract costs approximately $25 for a one-month supply. Grapefruit pectin runs $8 to $10 per month. Grapefruit seed extract costs $10 to $15 per month in liquid or capsule form.
About ten years ago, researchers inadvertently learned that grapefruit juice blocks enzymes involved in metabolizing certain medications, increasing the blood level of these drugs for an extended period of time (European Journal of Clinical Nutrition, 2004, vol. 58, no. 1). The medications include cholesterol-lowering drugs in the HMG-CoA reductase inhibitor family (such as lovastatin), calcium channel antagonists, benzodiazepines, and cyclosporine. Grapefruit extract and grapefruit seed extract supplements have not been associated with these effects, but it would be prudent to discuss this issue with your doctor.
Oregon-based freelancer Victoria Dolby Toews, MPH, is the author of the User’s Guide to Glucosamine and Chondroitin (Basic Health Publications, 2002).