Do Onions Help Lower Blood Sugar Levels in Diabetics?

The incidence of diabetes has risen dramatically over the past thirty years.  According to the CDC, the incidence of diabetes has risen from 3.3 to 8.2 per 1000 population from 1980 to 2008 in the United States.  That represents an increase of over 148%.  Part of this increase has been linked to the rising obesity epidemic in what has recently been coined the diabesity epidemic.

Diabetes itself is generally classified as one of three different types.  Type 1 diabetes refers to an autoimmune disease in which there is a defect in insulin secretion from the pancreas.  It accounts for 5-10% of the cases of diabetes and occurs most often in children and young adults.  In contrast, type 2 diabetes is a metabolic disorder characterized by a defect in insulin secretion and/or insulin resistance.  The third type is referred to as gestational diabetes which occurs in pregnant women.

Onions have long been known to have several putative health benefits.   Onions are rich in flavonoids such as quercetin as well as sulfur compounds.  The health benefits of onions have been linked to everything from the common cold due to diabetes and osteoporosis.

Anti-diabetic properties of red onion

Researchers from the department of pharmacology at the University of Gezira published the results of a preliminary study on the anti-diabetic properties of red onion (allium cepa) in the journal, Environmental Health Insights [1].  The purpose of their study was to investigate the hypoglycemic properties of red onion in patients with Type 1 and Type 2 diabetes.

The study itself included two groups of 21 patients each consisted of patients with either type 1 diabetes (group 1) or type 2 diabetes (group 2).  The patients included in this study were under the age of 50, not taking medicine for other health conditions, and did not smoke or consume alcohol.  The participants were given 100 g of red onion either while fasting or following an oral glucose tolerance test.

Type 1 diabetes results:

Fasting blood glucose was lowered by 145 mg/dl in response to administration of insulin (4 hours later).  In comparison, 100 g of allium cepa (red onion) resulted in an 89 mg/dl reduction in fasting blood glucose levels (4 hours later).

Next, this group participated in an oral glucose tolerance test (GTT) in which they were administered 75g of dextrose.  Insulin administration lowered their blood sugar by 152 mg/dl (4 hours later) while allium cepa resulted in a reduction of their blood sugar by 120 mg/dl.  Water alone was also used as a comparison and it resulted in a 77 mg/dl reduction in blood sugar levels fours hours after the dextrose challenge.

Type 2 diabetes results:

For fasting blood glucose levels, 100 g of crude red onion resulted in a 40 mg/dl reduction in blood glucose levels, four hours later.  In comparison, administration of 5 mg of the diabetes drug, glibenclamide, resulted in a reduction of 80 mg/dl.

Following the induced hyperglycemia (GTT), 100 g of allium cepa resulted in a 159 mg/dl reduction in blood glucose levels compared to water 55 mg/dl and glibenclamide 114 mg/dl.

Study conclusions:

The study authors succinctly concluded the following:

“Allium cepa in addition to its nutritional values has hypoglycemic effects that could be beneficial in management of type 1 and type 2 diabetic patients of all age groups, especially the level of its safety as reflected by its worldwide use as vegetable.”

Another interesting point made by the study authors was that they observed an increase in blood glucose levels after the first-hour following allium cepa administration which they attributed to the glucogenic effects of Allium cepa.  The study authors noted that this could counteract the common side effect, hypoglycemia of many anti-diabetic agents.

They also noted that the sample size in their study was too small to reach concrete conclusions but it seems apparent that Allium cepa or red onion does indeed have glucose-lowering properties which may be beneficial to those with diabetes.

Reference:

1. Environ Health Insights. 2010 Oct 14;4:71-7.