The extract of onion bulb, Allium cepa, is found to be effective in reducing high blood glucose (sugar) and total cholesterol levels. The study was presented at Endocrine Society's 97th Annual meeting in San Diego.

To three groups of rats with medically induced diabetes, lead investigator Ojieh ( MBBS (MD), MSc, of Delta State University in Abraka, Nigeria) and his colleagues gave metformin and varying doses of onion extract--200, 400 and 600 milligrams per kilograms of body weight daily (mg/kg/day) - to see if it would enhance the drug's effects. They also gave metformin and onion extract to three groups of non-diabetic rats with normal blood sugar, for comparison. Two control groups, one non-diabetic and one diabetic, received neither metformin nor onion extract. Another two groups (one with diabetes, one without) received only metformin and no onion extract. Each group contained five rats.

Two doses of onion extract, 400 and 600 mg/kg/day, strongly reduced fasting blood sugar levels in diabetic rats by 50 percent and 35 percent, respectively, compared with "baseline" levels at the start of the study before the rodents received onion extract, Ojieh reported. Allium cepa also reportedly lowered the total cholesterol level in diabetic rats, with the two larger doses again having the greatest effects.

The onion extract used for the experiment was a crude preparation from onion bulb, which is available in the local market. If this were to be administered to humans, it would usually be purified so that only the active ingredients would be quantified for adequate dosing, Ojieh said.