The Glycemic Index (GI) describes the rate of glucose disposal in the blood and is used to compare glycemic responses of different foods. Low GI foods are slowly digested and absorbed and so produce only small fluctuations in blood glucose and insulin levels. By contrast, high GI foods are rapidly digested and absorbed, producing a more pronounced fluctuation in blood glucose levels.

The glycemic index (GI) ranks carbohydrates on a scale from 0 to 100 as follows:

• Low GI foods = GI less than 55
• Intermediate GI foods = GI between 55 and 70
• High GI foods = GI greater than 70

Low-GI foods have proven health benefits, such as improving both glucose and lipid levels in people with diabetes (type 1 and type 2) and helping control appetite and delay hunger for weight control. Adopting a low GI eating pattern has also been shown to reduce insulin levels and insulin resistance.

For people with diabetes, the recommendation is to make low to intermediate GI foods the focus of their day-to-day diet. It isn’t necessary to exclude all high GI foods, provided lower GI foods are the mainstay of the diet.

The GI of Legumes:

Legumes are a source of slowly digestible carbohydrates, giving them the broad status of ‘low GI’ foods. A large number of published research studies have verified the low GI status of various legume types and legume food forms compared to controls (including white bread, glucose or dextrose), with all studies showing that legumes have a significantly lower GI than the controls.

With respect to postprandial studies comparing legumes or legume products (with doses ranging from 30 to 762 g) to controls (e.g. potatoes, rice, white bread, pasta, grains, glucose, isolated fibers etc), more than 30 papers have been published. In these studies, the majority (~83%) found significant reductions in postprandial peak glucose or area under the curve (AUC) compared to the control.

A recent systematic review and meta-analysis of randomised controlled experimental trials investigated the effect of pulses on markers of glycemic control in people with and without diabetes. It was found that when eaten on their own, legumes significantly lowered fasting blood glucose and insulin levels. In trials where legumes were included in low GI diets and high fibre diets, the legumes significantly lowered  glycosylated blood proteins (HbA1C). Of most worthy note was that in subjects with type 2 diabetes, the significant reduction in HbA1C was comparable to that achieved by medication.

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