Abstract
Objectives:Low glycaemic index (GI) foods are recommended to improve glycaemic control in diabetes; however, Health Canada considers that GI food labeling would be misleading and unhelpful, in part, because selected studies suggest that GI values are inaccurate due to an effect of ethnicity. Therefore, we conducted a systematic review and meta-analysis to compare the GI of foods when measured in Caucasians versus non-Caucasians.Methods:We searched MEDLINE, EMBASE and Cochrane databases for relevant articles. GI differences were aggregated using the generic inverse variance method (random effects model) and expressed as mean difference (MD) with 95% confidence intervals (95% CI). Study quality was assessed based on how well studies complied with official international GI methodology.Results:Review of 1288 trials revealed eight eligible studies, including 28 comparisons of GI among 585 non-Caucasians and 971 Caucasians. Overall, there was borderline significant evidence of higher GI in non-Caucasians than Caucasians (MD, 3.3 (95% CI, −0.1, 6.8); P=0.06) with significant heterogeneity (I2, 46% P=0.005). The GI of eight types of rice was higher in non-Caucasians than Caucasians (MD, 9.5 (95% CI, 3.7, 23.1); P=0.001), but there was no significant difference for the other 20 foods (MD, 1.0 (95% CI, −2.5, 4.6); P=0.57). MD was significantly greater in the four low-quality studies (nine comparisons) than the four high-quality studies (19 comparisons; 7.8 vs 0.7, P=0.047).Conclusions:With the possible exception of rice, existing evidence suggests that GI values do not differ when measured in Caucasians versus non-Caucasians. To confirm these findings high-quality studies using a wide range of foods are required.
Highlights
The glycaemic index (GI) is conceptually defined as the incremental area under the blood glucose response curve (AUC) elicited by a portion of food containing 50 g available carbohydrate expressed as a percentage of that elicited by 50 g glucose in the same subjects
In order for a study to be included, glucose responses had to have been measured over 2 h in subjects without diabetes, incremental AUC calculated appropriately, the reference food had to be glucose or white bread, the portions of foods tested had to contain the same amount of available carbohydrate as the portions of the reference food, and the results for the individual foods had to be given
The only exceptions were as follows: (1) pooled results for two foods measured in Caucasians and non-Caucasians were reported in our interlaboratory study,[4] but we report here results for each food separately; (2) one study determined the glycemic response of 50 g maltitol relative to g glucose; 50 g maltitol does not contain 50 g available carbohydrate, the study included the results that represent a glycemic response relative to that of glucose.[5]
Summary
The glycaemic index (GI) is conceptually defined as the incremental area under the blood glucose response curve (AUC) elicited by a portion of food containing 50 g available carbohydrate expressed as a percentage of that elicited by 50 g glucose in the same subjects. There is much evidence that GI is a relevant marker of carbohydrate quality associated with health benefits, both for people with and without diabetes.[1] The Canadian Diabetes Association recommends the use of low-GI foods to improve glycaemic control.[2] it is difficult for consumers and health professionals to obtain reliable information about the GI of specific foods because GI labeling of foods is not allowed in Canada. It was suggested that the GI method is inaccurate because the result obtained may depend upon the ethnicity of the subjects in whom it is measured;[3] this conclusion was not based on a systematic review of the literature. Our purpose was to conduct a systematic review and meta-analysis to determine whether the GI of foods differs when GI is measured in Caucasian versus non-Caucasian subjects
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