Effect of a High-Protein, Low-Carbohydrate Diet on Blood Glucose Control in People With Type 2 Diabetes

Abstract

There has been interest in the effect of various types and amounts of dietary carbohydrates and proteins on blood glucose. On the basis of our previous data, we designed a high-protein/low-carbohydrate, weight-maintaining, nonketogenic diet. Its effect on glucose control in people with untreated type 2 diabetes was determined. We refer to this as a low-biologically-availableglucose (LoBAG) diet. Eight men were studied using a randomized 5-week crossover design with a 5-week washout period. The carbohydrate:protein:fat ratio of the control diet was 55:15:30. The test diet ratio was 20:30:50. Plasma and urinary ␤-hydroxybutyrate were similar on both diets. The mean 24-h integrated serum glucose at the end of the control and LoBAG diets was 198 and 126 mg/dl, respectively. The percentage of glycohemoglobin was 9.8 ؎ 0.5 and 7.6 ؎ 0.3, respectively. It was still decreasing at the end of the LoBAG diet. Thus, the final calculated glycohemoglobin was estimated to be ϳ6.3-5.4%. Serum insulin was decreased, and plasma glucagon was increased. Serum cholesterol was unchanged. Thus, a LoBAG diet ingested for 5 weeks dramatically reduced the circulating glucose concentration in people with untreated type 2 diabetes. Potentially, this could be a patient-empowering way to ameliorate hyperglycemia without pharmacological intervention. The long-term effects of such a diet remain to be determined. Diabetes 53:2375-2382, 2004 D ata obtained in our laboratory (1-3) as well as from others (reviewed in 4) indicate that glucose that is absorbed after the digestion of glucose-containing foods is largely responsible for the rise in the circulating glucose concentration after ingestion of mixed meals. Dietary proteins, fats, and absorbed fructose and galactose resulting from the digestion of sucrose and lactose, respectively, have little effect on blood glucose concentration.We and others also have reported that even short-term starvation (hours) results in a dramatic decrease in the blood glucose concentration in people with type 2 diabetes (5). This seems to be due largely to a rapid, progressive decrease in the rate of glycogenolysis (5,6). Hepatic glycogen stores in turn are dependent on the content of carbohydrate in the diet (6). Thus, a reduced-carbohydrate diet should result in a lower overnight fasting glucose concentration.To test the hypothesis that a diet that is low in carbohydrate and particularly low in food-derived glucose could lower both the fasting and the postprandial blood glucose in people with type 2 diabetes, we designed a lowcarbohydrate diet in which readily digestible starch-containing foods have been de-emphasized. However, the carbohydrate content is sufficient to prevent ketosis. This is in contrast to the low-carbohydrate diets being advocated for weight loss (7). We refer to this as a lowbiologically-available-glucose (LoBAG) diet. In our study, we also attempted to ensure weight stability. The effect of 5 weeks of this diet on percentage glycohemoglobin and 24-h glucose, insulin, C-peptide, ␤-hydroxybuty...

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