Article

Another approach to estimating the reliability of glycaemic index

Department of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, PO Box 913, Dunedin, New Zealand.
The British journal of nutrition (Impact Factor: 3.45). 09/2008; 100(2):364-72. DOI: 10.1017/S0007114507894311
Source: PubMed

ABSTRACT

The usefulness of the glycaemic index (GI) of a food for practical advice for individuals with diabetes or the general population depends on its reliability, as estimated by intra-class coefficient (ICC), a measure having values between 0 and 1, with values closer to 1 indicating better reliability. We aimed to estimate the ICC of the postprandial blood glucose response to glucose and white bread, instant mashed potato and chickpeas using the incremental area under the curve (iAUC) and the GI of these foods. The iAUC values were determined in twenty healthy individuals on three and four occasions for white bread and glucose, respectively, and for potato and chickpeas on a single occasion. The ICC of the iAUC for white bread and glucose were 0.50 (95 % CI 0.27, 0.73) and 0.49 (95 % CI 0.22, 0.75), respectively. The mean GI of white bread was 81 (95 % CI 74, 90) with a reliability of 0.27 indicating substantial within-person variability. The GI of mashed potato and chickpeas were 87 (95 % CI 76, 101) and 28 (95 % CI 22, 37) respectively with ICC of 0.02 and 0.40.The ICC of the iAUC were moderate and those of the GI fair or poor, indicating the heterogeneous nature of individuals' responses. The unpredictability of individual responses even if they are the result of day-to-day variation places limitations on the clinical usefulness of GI. If the very different GI of potato and chickpeas are estimates of an individual's every-day response to different foods, then the GI of foods may provide an indication of the GI of a long-term diet.

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Available from: Tim John Green, Feb 03, 2014
    • "n u t r i t io n j r n l . c o m Nutrition 31 (2015) 539–541 Although the quantitative individual responses to a given food or meal can be quite variable from day to day [22] [23], the glycemic index provides useful relative estimates of an individual's glycemic responses to consumed foods, and the GI of food items and of mixed-food meals are relatively good indicators of the effect of the consumption of food items and meals on postprandial insulin secretion. In free-living adults, the calculated GI of meals is highly significantly correlated with, and predictive of, postprandial plasma insulin concentrations [9,15, 16,24–29]. "

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    • "Therefore, variation in the measurement of GI can be attributed to day-to-day variation and random fluctuations in individual glycemic response (Williams et al., 2008). Some variation in blood glucose can be reduced by controlling the consumption of food the day before a testing session (Granfeldt, Wu, & Björck, 2006), which, along with standardization of prior exercise, is common in sport nutrition research (Burke, Collier, & Hargreaves, 1998), and by conducting tests of both the reference food (Wolever, 2003) and the test food at least twice in each participant (Venn & Green, 2007; Williams et al., 2008). However, although duplicate testing of the reference food is common in GI research, duplicate testing of the test foods is not common practice in either GI or sport nutrition research. "
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    ABSTRACT: The aim of this review is to provide an up-to-date summary of the evidence surrounding glycemic index (GI) and endurance performance. Athletes are commonly instructed to consume low-GI (LGI) carbohydrate (CHO) before exercise, but this recommendation appears to be based on the results of only a few studies, whereas others have found that the GI of CHO ingested before exercise has no impact on performance. Only 1 study was designed to directly investigate the impact of the GI of CHO ingested during exercise on endurance performance. Although the results indicate that GI is not as important as consuming CHO itself, more research in this area is clearly needed. Initial research investigating the impact of GI on postexercise recovery indicated consuming high-GI (HGI) CHO increased muscle glycogen resynthesis. However, recent studies indicate an interaction between LGI CHO and fat oxidation, which may play a role in enhancing performance in subsequent exercise. Despite the fact that the relationship between GI and sporting performance has been a topic of research for more than 15 yr, there is no consensus on whether consuming CHO of differing GI improves endurance performance. Until further well-designed research is carried out, athletes are encouraged to follow standard recommendations for CHO consumption and let practical issues and individual experience dictate the use of HGI or LGI meals and supplements before, during, and after exercise.
    Full-text · Article · Apr 2010 · International journal of sport nutrition and exercise metabolism
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    • "Therefore, variation in the measurement of GI can be attributed to day-to-day variation and random fluctuations in individual glycemic response (Williams et al., 2008). Some variation in blood glucose can be reduced by controlling the consumption of food the day before a testing session (Granfeldt, Wu, & Björck, 2006), which, along with standardization of prior exercise, is common in sport nutrition research (Burke, Collier, & Hargreaves, 1998), and by conducting tests of both the reference food (Wolever, 2003) and the test food at least twice in each participant (Venn & Green, 2007; Williams et al., 2008). However, although duplicate testing of the reference food is common in GI research, duplicate testing of the test foods is not common practice in either GI or sport nutrition research. "

    Full-text · Article · Jan 2010 · International journal of sport nutrition and exercise metabolism
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