A new study from the University of Guelph shows that replacing half of the available carbohydrates from potatoes or rice with cooked lentils can lower blood glucose levels by more than 20% in healthy adults. The study appears in the Journal of Nutrition.
Lentils significantly reduce blood glucose. Image credit: Maxmann.
“Pulses, such as lentils, are extremely nutrient-dense food that have the potential to reduce chronic diseases associated with mismanaged glucose levels,” said Professor Alison Duncan, from the Department of Human Health and Nutritional Sciences at the University of Guelph.
“They contain components that inhibit enzymes involved in absorption of glucose, and fiber contained in these foods can encourage the production of short-chain fatty acids, which can also help to reduce blood glucose levels.”
In the study, Professor Duncan and co-authors aimed to determine the extent to which the blood glucose response is lowered when half of the available carbohydrates from rice or potato is replaced with cooked lentils.
They involved 24 healthy adults fed four dishes: white rice only, half white rice and half large green lentils, half white rice and half small green lentils, and half white rice and half split red lentils.
They measured glucose levels in the participants’ blood before they ate and during two hours afterward. They repeated the process for white potatoes alone and the same combinations of potatoes and lentils.
“We mixed the lentils in with the potatoes and rice because people don’t typically eat pulses on their own, but rather consume them in combination with other starches as part of a larger meal, so we wanted the results to reflect that,” Professor Duncan explained.
Blood glucose fell by similar amounts when half of the starch was replaced with each of the three types of lentils.
“Replacing half a serving of rice with lentils caused blood glucose to drop by up to 20%,” the scientists said.
“Replacing potatoes with lentils led to a 35% drop.”
Blood glucose comprises sugar found in the blood during digestion in the upper digestive tract and depends on the starch content of foods consumed.
Pulses can slow digestion and the release of sugars found in starch into the bloodstream, ultimately reducing blood glucose levels.
“This slower absorption means you don’t experience a spike in glucose,” Professor Duncan said.
“Having high levels over a period of time can lead to mismanagement of blood glucose, which is the hallmark of type 2 diabetes. Essentially, eating lentils can lower that risk.”
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Dita Moravek et al. 2018. Carbohydrate Replacement of Rice or Potato with Lentils Reduces the Postprandial Glycemic Response in Healthy Adults in an Acute, Randomized, Crossover Trial. Journal of Nutrition 148 (4): 535-541; doi: 10.1093/jn/nxy018
