Current issues of ACP Journal Club are published in Annals of Internal Medicine


Therapeutics

Low glycemic index foods improved long-term glycemic control in NIDDM

ACP J Club. 1991 July-Aug;115:19. doi:10.7326/ACPJC-1991-115-1-019


Source Citation

Brand JC, Colagiuri S, Crossman S, et al. Low-glycemic index foods improve long-term glycemic control in NIDDM. Diabetes Care. 1991 Feb;14:95-101. [PubMed ID: 2060429]


Abstract

Objective

To determine whether a low-glycemic index (GI) diet improves glycemic control and lipid metabolism in patients with non-insulin-dependent diabetes mellitus (NIDDM).

Design

Patients were assigned to 12-week high-GI and 12-week low-GI diets in random order, separated by a 3-week period.

Setting

Referral pattern not stated.

Patients

16 well-controlled, otherwise healthy diabetic patients (mean age, 62 y) with an insidious onset and mean duration of NIDDM of 5 years were studied. All patients were on diabetic diets; 10 were treated with sulfonylureas.

Intervention

7 patients were randomized first to the high-GI diet and 9 to the low-GI diet. The GI of a food relates the area under the postprandial glucose curve of a food to that of a reference food, such as glucose, with the same carbohydrate value. The low-GI diet emphasized nonwheat cereals, pasta, and legumes, and restricted potatoes, bananas and other high-GI fruits and vegetables, but not bread. A dietician counselled patients at home and assessed compliance. Prestudy medication was not altered.

Main outcome measures

After each dietary period, weight, glycosylated hemoglobin, fasting plasma glucose, C-peptide, insulin, lipids, and the metabolic response to a standard meal were measured.

Main results

The diets did not differ in total energy, fat, carbohydrate, or fiber content; the energy contribution of sugars (minus lactose) was smaller and that of protein was higher in the low-GI diet (P < 0.05). Mean glycosylated hemoglobin at the end of 12 weeks was 11% lower on the low-GI diet (7.0% {95% CI 6.4% to 7.6%}*) than on the high-GI diet (7.9% {CI 6.9% to 8.9%}* P < 0.05). No differences existed between the effects of low- and high-GI diets on body weight, fasting plasma glucose, insulin, C-peptide, total cholesterol, triglycerides, or lipoproteins. Patients had lower 8-hour plasma glucose responses to standard meals at the end of the 12-week low-GI period compared with the high-GI period (P < 0.05).

Conclusions

Patients with well-controlled NIDDM showed improved glycemic control after 12 weeks on a low-glycemic index diet. Serum lipid profiles were not affected.

Sources of funding: Sydney University Nutrition Research Foundation; CSL-Novo Pty., Ltd.; Apex-Australian Diabetes Foundation.

Address for article reprint: Dr. J.C. Brand, Human Nutrition Unit, G08, The University of Sydney, Sydney, NSW 2006, Australia.

*Numbers calculated from data in article.


Commentary

The ideal diet for a person with diabetes is still controversial. Competing but individually important goals have to be reconciled; the diet should be low in simple carbohydrates to control glycemia, low in fats to lower the risk for atherosclerosis, and most recently added, low in protein to prevent or at least reduce the risk for end-stage renal disease (1). What does this leave other than complex carbohydrates? Some investigators are concerned that increasing the carbohydrate content of a diabetic diet will worsen glycemic control and may also increase triglycerides. Conversely, foods with high soluble fiber content (such as legumes) have been shown to improve glycemic control. The glycemic index was developed in an effort to identify optimal carbohydrates. Short-term studies of individual foods showed clear differences among types of carbohydrates (e.g., potatoes vs pasta). These differences, however, varied from study to study when single-meal comparisons were made of carbohydrates of different glycemic potential (2). The study by Brand and colleagues is notable in that it effectively shows the benefits to glycemic control of low-glycemic index foods over time.

This well-designed study adds to our knowledge of ways to tailor the diabetic diet to the individual to make it more acceptable; further work is needed to see if similar results can be achieved in clinical settings where close monitoring of dietary adherence is less available.

Jacqueline A. Pugh, MD
Audie L. Murphy Memorial Veterans HospitalSan Antonio, Texas, USA.


References

1. Lebovitz H, ed. Physicians' Guide to Non-Insulin-Dependent (Type II) Diabetes: Diagnosis and Treatment. 2d ed. Alexandria, Virginia: American Diabetes Association;1988:26-31.

2. Hollenbeck CB, Coulston AM, Reaven GM. Comparison of plasma glucose and insulin responses to mixed meals of high-, intermediate-, and low-glycemic potential. Diabetes Care. 1988;11:323-9.