Study Shows Benefits of a Low-Glycemic Diet

A low-glycemic diet brings small but valuable benefits to people with diabetes, reports a study published in The BMJthe weekly journal of the British Medical Association.

What is a low glycemic diet? To quote the authors of the article, “The glycemic index (GI) ranks a carbohydrate containing food according to the amount by which it raises blood glucose levels after it is consumed in comparison with reference food (pure glucose or white bread), for which a GI of ≤55 is low, 56-69 is medium, and ≥70 is high, based on a glucose scale.” In other words, the GI classifies carbohydrate-containing foods according to how quickly they raise blood sugar and foods with a GI of 55 or less are considered low-GI. Some low-GI foods are non-starchy vegetables such as peppers, broccoli, lettuce, and eggplant; fruits in limited quantities (pears, apples, cranberries, peaches, strawberries, and blueberries, and so on); beans; milk and yogurt; certain nuts like almonds, peanuts, and walnuts; and lean meats, fish, turkey, and chicken.

A low-glycemic diet, then, is one that’s rich in these foods. A low-calorie diet is not necessarily a low-GI diet. Watermelon, for example, has a high GI, and so do some breakfast cereals. Although the benefits of a low-GI diet have been recognized in the past, the researchers pointed out that the last time the European Association for the Study of Diabetes updated their recommendation on GI dietary patterns for people with diabetes was in 2004.

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The researchers collected 27 randomized controlled trials published up to May 2021 that studied the effects of low-GI diets. These trials contained data on 1,617 subjects who had either type 1 or type 2 diabetes. Most were overweight, middle-aged (although some children as young as 11 were included), and used medications or insulin to control their diabetes. In most of the studies the ratio of men to women was about 50-50. The researchers used a grading system to rank the evidence as high, moderate, low, or very low certainty. The studies reviewed were conducted in various countries; most were in Canada (21%) and Australia (17%, but others were in France (10%), the United States (7%), Israel (7%), Mexico (7%), and other European and Asian countries .

Benefits linked to low-GI diets

The data collected from all the trials showed that low-GI dietary patterns reduced HbA1c (A1C, the measure of a person’s blood glucose over the preceding two to three months) compared to higher-GI diets. The results also showed reductions in other risk factors — body weight, fasting glucose, LDL cholesterol (often called “the bad cholesterol”), and C-reactive protein (a measure of inflammation). Although these reductions were not dramatic, the researchers described them as small but important. The review did not report improvements in insulin levels, waist circumference, HDL cholesterol, and blood pressure, although the authors acknowledged the relative scarcity of information on blood pressure.

The authors concluded that “Diet and lifestyle remain the cornerstone of the management of diabetes,” while adding that a low-GI diet “might be an especially helpful lifestyle strategy for those with Type 2 diabetes as it might assist in the management of glycemic control as add-on treatment to hyperglycemia drugs while at the same time reducing the need for these drugs.” All in all, the researchers stated that the results of the study demonstrate that a low-GI diet is “considered an acceptable and safe dietary strategy that can produce small meaningful reductions in the primary target for glycemic control in diabetes, HbA1c fasting glucose, and other established cardiometabolic risk factors.”

Want to learn more about eating well with diabetes? Read “Strategies for Healthy Eating” and “Easy Ways to Eat Better.”

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