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Department of Paediatrics
San Paolo Hospital
University of Milan
Via A di Rudinì 8
I-20142 Milan
Italy
E-mail: silvia.scaglioni{at}unimi.it
Dear Sir:
We read with interest the letters by Mendosa (1) and Brand-Miller et al (2) in the April 2003 issue of the Journal. In those letters, the authors wondered whether data on glycemic load were available in a healthy pediatric population and whether the type of relation between glycemic load and blood insulin concentrations had been investigated.
We studied the relations of dietary glycemic load (GL) and overall glycemic index (OGI) with glucose and insulin concentrations in a population of healthy 8-y-old children. The trial design, eligibility criteria, and sampling methods were described previously (3). Of 164 healthy newborns who were randomly selected from all live births that occurred from August to December 1991, data at the age of 8 y were available for 111 children (105 were classified as normal weight and 6 were classified as overweight on the basis of criteria from the International Obesity Task Force; 4). Anthropometric variables (body weight and length), body mass index, nutritional habits, and biochemical data on serum insulin and glucose were evaluated. The children's dietary habits were evaluated on the basis of a previously validated (5), age-adjusted food-frequency questionnaire, which was designed according to Block's approach (6). Dietary GL and OGI were calculated by using the method of Liu et al (7) and reference tables for glycemic index (8). Student's t test and the nonparametric Mann-Whitney U test were used to analyze between-sex differences in continuous variables. Analysis of variance and the Kruskal-Wallis test were used to analyze differences in continuous variables between tertiles of GL or OGI.
In agreement with the significantly higher energy and carbohydrate intakes found in the boys than in the girls, GL values were significantly higher in the boys than in the girls, but the boys and the girls did not differ significantly in OGI. Mean (±SD) values of GL and OGI were 145 ± 37 and 58 ± 2, respectively. The distribution of percentage of energy intake from macronutrients did not differ significantly between the boys and the girls, and the average values were 15% of energy from protein, 56% from carbohydrates, and 29% from fats. Serum insulin concentrations were in the normal range and were positively associated with OGI (P = 0.03) but not with GL (P = 0.5). No significant associations were found between body mass index and either GL or OGI.
We calculated mean daily dietary intake according to tertiles of GL and OGI. After adjustment for total energy intake, body mass index, and sex, GL was found to be positively associated with total carbohydrates and starch and negatively associated with total, saturated, monounsaturated, and polyunsaturated fat. Accordingly, we found negative associations of OGI with total proteins, soluble carbohydrates, and soluble and insoluble fiber. GL was positively associated with energy intake and intake of carbohydrates from high-starch foods and negatively associated with fat and major fat families. With regard to individual food items, GL was positively associated with intakes of pasta, white bread, cooked potatoes, bakery products, and cookies.
In conclusion, GL may be an indicator of the general quality of the diet, whereas OGI seems to be associated with the quality of ingested carbohydrates and is correlated with insulin concentrations. In our study, a low OGI corresponded with a high intake of fiber-rich products (legumes and carrots) and a low intake of cookies and white bread. A low OGI may benefit the glucose-insulin axis while flattening the glycemic response.
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