Low glycemic index (LGI) diets have been shown to improve glucose tolerance in clinical studies; however, this does not necessarily ensure similar effectiveness when given to free-living individuals making their own food choices. This concern was reflected in the current position of the American Diabetes Association (1) in that “although LGI foods may reduce postprandial hyperglycemia, there is insufficient evidence of long-term benefits to recommend general use of LGI diets in type 2 diabetic patients.” Despite this, the glycemic index (GI) method for classifying carbohydrates has been endorsed by a number of influential bodies, including the Food and Agriculture Organization of the United Nations/World Health Organization joint committee. Commonly consumed LGI foods include pasta, noodles, and fruit; however, others such as lentils, beans, and peas have limited acceptance. In a previous study (2), we successfully used the substitution of a key carbohydrate food at each meal to reduce the overall GI of the diet.
The MiniMed continuous glucose monitoring system (CGMS) is based on the electrochemical detection of subcutaneous interstitial fluid and can be operated in situ for up to 3 days (3). It records values in a pager-sized monitor every 5 min, providing 288 glucose readings every 24 h.
The aim of this study was to examine the effects of an LGI diet consumed for 7 days by free-living patients with type 2 diabetes who were monitored for two 24-h periods using the CGMS.
A total of 18 people who were attending Hammersmith Hospitals Trust diabetes clinic for treatment of type 2 diabetes agreed to participate. Four people dropped out. Of the final 14 participants (aged 54 ± 7 years, HbA1c 8.1 ± 1.4%, and BMI 39.0 ± 13.5 kg/m2), 6 patients were receiving insulin in addition to oral hypoglycemic agents. No change in medication occurred over the study period.
A reduction in the GI of the diet occurred during the 24-h monitoring period (57 ± 2 vs. 49 ± 1, P < 0.001) in 11 of 14 subjects, whereas energy and other macronutrients remained constant. In these 11 patients there was a significant reduction in fasting glucose at 6 a.m. (8.0 ± 1.0 vs. 5.3 ± 0.8 mmol/l, P < 0.01), mean glucose (8.9 ± 1.0 vs. 7.5 ± 0.1 mmol/l, P < 0.02), 24-h area under the curve (AUC) for glucose (12,844 ± 1,354 vs. 10,839 ± 832 mmol/l per min, P < 0.04), and overnight 8-h AUC glucose (4,315 ± 590 vs. 3,428 ± 261 mmol/l per min, P < 0.05) (Fig. 1).
Our study highlights the benefits of an LGI diet in free-living patients with type 2 diabetes and the potential for CGMS to provide valuable information on glycemic excursions that would be missed by more conventional monitoring. An LGI diet can dramatically improve a patient’s glycemic control within a short period; if achievable over the longer term, this may contribute to a decrease in diabetic complications.
Mean 24-h AUC for glucose at baseline (——) and in response to an LGI (----) after 7 days (n = 11).
Mean 24-h AUC for glucose at baseline (——) and in response to an LGI (----) after 7 days (n = 11).
References
Address correspondence to Gary Frost, Department of Nutrition and Dietetics, Hammersmith Hospital, Du Cane Road, London W12 OHS. E-mail: [email protected].
