High-Protein Diet Helpful in Type 2 Diabetes

Laurie Barclay, MD

October 06, 2003

Oct. 6, 2003 — A five-week high-protein diet improves glycemic control and lipid profiles without adversely affecting renal function in type 2 diabetes, according to the results of a study published in the October issue of the American Journal of Clinical Nutrition. The editorialist praises the study design, but all agree that long-term outcomes studies are now needed.

"In single-meal studies, dietary protein does not result in an increase in glucose concentrations in persons with or without type 2 diabetes, even though the resulting amino acids can be used for gluconeogenesis," write Mary C. Gannon, from the Department of Veterans Affairs Medical Center in Minneapolis, Minnesota, and colleagues. "The metabolic effects of a high-protein diet were compared with those of the prototypical healthy (control) diet, which is currently recommended by several scientific organizations."

Twelve subjects with untreated type 2 diabetes consumed a high-protein diet and a control diet for five weeks each, separated by a two- to five-week washout period. The ratio of protein to carbohydrate to fat was 30:40:30 in the high-protein diet and 15:55:30 in the control diet. Weight remained stable throughout the study.

Using the fasting glucose concentration as a baseline to determine the area under the curve, there was a 40% decrease in the mean 24-hour integrated glucose area response after the high-protein diet. Patients on the high-protein diet also fared better in terms of decrease in glycated hemoglobin (0.8% vs. 0.3%; P < .05); greater rate of change over time ( P < .001); and lower fasting triacylglycerol ( P < .03). Insulin, C-peptide, and free fatty acid concentrations were similar after both diets, and microalbumin and creatinine clearance were unchanged.

"A high-protein diet lowers blood glucose postprandially in persons with type 2 diabetes and improves overall glucose control," the authors write. "However, longer-term studies are necessary to determine the total magnitude of response, possible adverse effects, and the long-term acceptability of the diet."

The American Diabetes Association, the Minnesota Beef Council, and the Colorado and Nebraska Beef Councils and Merit Review Funds from the Medical Research Service, Department of Veterans Affairs, Minneapolis, helped support this study.

In an accompanying editorial, R. H. Eckel, from the University of Colorado Health Sciences Center in Denver, praises the study design but notes that the sample size was small and the duration of the study was limited.

"The substitution of dietary protein for carbohydrate may improve glycemic control without increasing the risk of atherosclerosis," he writes. "The stage is set for long-term studies that use different food sources of dietary protein and to determine the relevance of increasing dietary protein in patients with more complicated diabetes."

Am J Clin Nutr. 2003;78:671-672, 734-741

Reviewed by Gary D. Vogin, MD


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