Today’s post comes from Dr. Donald Layman. Dr. Layman is the Director of Research at the Egg Nutrition Center and Professor Emeritus at the University of Illinois and a leading researcher studying dietary needs for protein and amino acids.
A recent review by Dr. Acheson in the European Journal of Clinical Nutritionhighlights a paradigm shift in medical practice for management of type 2 diabetes (T2D).The shift is from recommending high carbohydrate diets combined with drugs therapies to regulate blood glucose to a new philosophy for use of low carbohydrate diets to reduce glucose exposure and minimize drug needs.The principles underpinning this shift reflect new understanding about how the body regulates blood glucose. The fundamental problem in diabetes is elevated blood glucose causing vascular damage throughout the body including the eyes, heart, and kidneys.
For most of the past century, diet and drug therapies have been aimed at increasing disposal of blood glucose in muscle and adipose. Standard treatments included high carbohydrate, low fat diets, insulin, and oral hypoglycemic drugs (ie. sulfonylurea [SU] and thiazolidinedione [TZD]). These approaches largely controlled blood glucose by accelerating glucose uptake into adipose tissue but the obvious side effect was increasing body fat and obesity.
The new philosophy emphasizes use of reduced carbohydrate, higher protein diets with limited drug therapy and is being used at leading medical centers including the “Why WAIT” program at Joslin Diabetes Center (Curr Diab Rep 8:413,2008). This philosophy shifts the focus of glycemic regulation to dietary control of glucose exposure. By limiting glucose intake, the liver regulates the entry of glucose into the blood, minimizes the need for insulin, and reduces side effects of obesity. Metformin becomes the primary drug because it helps regulate glucose release by the liver. These programs have been shown to be highly effective for treatment of T2D and for weight loss.
In the late 1920’s, research showed that in normal subjects consumption of high carbohydrate diets increased glucose use. In other words, the more carbohydrates you eat, the more efficient you would become at regulating blood glucose. This philosophy was further supported in the 1950’s with the availability of insulin and the potential to assist the pancreas with more insulin to regulate blood glucose. Many of the current approaches to diabetes management try to control blood glucose by stimulating disposal into peripheral tissues – namely muscle and adipose.
The debate about the ideal diet for weight management often concludes that calories are the critical factor and specific macronutrient content is not important. Then, a logical assumption that controlling fat intake is important because of the higher energy density and potential negative effects on cardiovascular health. While there is intuitive logic for controlling total calories and dietary fat, evidence is accumulating that weight management is best achieved with a focus on reducing excess carbohydrate intake and maintaining dietary protein.
While Americans consume a higher percentage of dietary fat than current recommendations, the RDA for carbohydrates is 130 g/day and the average intake is about 300 g/day. So if all calories are equally important, then consumption of nearly three times more carbohydrates than the RDA is a major contribution to energy excess.
Emerging evidence suggests moving from high carbohydrate, low fat diets combined with drug therapy to diets with reduced carbohydrates and higher protein. Since insulin became available in the 1950’s, the treatment philosophy has been that use of supplemental insulin and/or hypoglycemic drugs combined with a high carbohydrate low fat diet was the best combination to control blood glucose and reduce the risk of heart disease. This treatment approach has not proven to enhance long-term outcomes, and the incidence of type 2 diabetes is increasing rapidly. Researchers and physicians are now looking at virtually the opposite approach, to reduce dietary carbohydrate intake and reduce the reliance on drug therapy.