Type 2 diabetes means that the pancreas does not make enough insulin to regulate blood sugar or the insulin it produces is not taken up by cells. Insulin regulates blood sugar – the main type of sugar found in blood. Without this mechanism, blood sugar levels can rise to dangerous levels. Fortunately, there is an effective countermeasure at hand.
According to findings presented Thursday at the 97th annual meeting of The Endocrine Society in San Diego, onion bulb extract, Allium cepa, greatly reduced high blood glucose (sugar) and total cholesterol levels in diabetic rats when given with the antidiabetic drug metformin.
“Onion is cheap and available and is used as a dietary supplement,” said lead researcher Anthony Ojieh, MBBS (MD), MSc, of Delta State University in Abraka, Nigeria.
“It has the potential for use in treating patients with diabetes.”
To three groups of rats with medically induced diabetes, Mr. Ojieh and his colleagues gave metformin and various doses of onion extract – 200, 400 and 600 milligrams per kilogram of body weight per day (mg/kg/day) to see if it would enhance the effects of the medicine.
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For comparison, they also gave metformin and onion extract to three groups of non-diabetic rats with normal blood sugar levels.
Two control groups, one non-diabetic and one diabetic, received neither metformin nor onion extract.
Two more 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, greatly reduced fasting blood sugar in diabetic rats by 50 percent and 35 percent, respectively, compared to the “baseline” values at the beginning of the study before the rodents were given onion extract, reported Mr Ojieh.
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Allium cepa also reportedly lowered total cholesterol levels in diabetic rats, with the two larger doses again having the greatest effects.
Onion extract led to an increase in mean weight in non-diabetic rats, but not in diabetic rats.
“Onions aren’t very high in calories,” Ojieh says. “However, it appears to increase metabolism and thereby increase appetite, leading to an increase in nutrition.”
“We need to investigate the mechanism by which onion caused the blood glucose lowering,” said Mr. Ojieh. “We don’t have an explanation yet.”
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The study, which also involved scientists from Cranfield University in the UK, found that the brown skin and outer layers of onions contain beneficial amounts of fiber and flavonoids, and that the bulbs contain sulfur-containing compounds and fructans.
The study showed that because the brown skin of the onion is rich in dietary fiber, it can be used as a functional ingredient, and two outer fleshy layers also contain fiber and flavonoids and have a high antioxidant capacity.
Researcher Vanesa Benitez noted, “One solution could be to use onion waste as a natural source of ingredients with high functional value, as this vegetable is rich in compounds that provide benefits for human health.”
She added, “Eating fiber reduces the risk of cardiovascular disease, gastrointestinal upset, colon cancer, type 2 diabetes and obesity.”