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08-08-2011 | Diabetes | Article

Glycemic index, not load, predicts diabetes in middle-aged Japanese men

Abstract

Free abstract

MedWire News: Dietary glycemic index (GI) is associated with the incidence of diabetes in middle-aged Japanese men, report researchers.

The study supports previous findings that GI, not glycemic load (GL), is associated with incidence of diabetes, making it a better predictor of the risk for diabetes than GL, say the researchers.

As reported in the journal Metabolism, Masaru Sakurai (Kanazawa Medical University, Ishikawa, Japan) and colleagues investigated the association between GI, GL, and the incidence of diabetes in a cohort of 1995 male factory workers, aged 33-35 years, in Japan between 2003 and 2009. They also analyzed the effects of insulin resistance and pancreatic B-cell function on the association.

The team analyzed data from the employees' annual health examinations, which included a medical history, physical examination, anthropometric measurements, as well as fasting plasma glucose, fasting insulin, glycated hemoglobin (HbA1c), and serum lipid levels.

They used the homeostasis model assessment (HOMA) to quantify insulin resistance (HOMA-IR) and they also calculated the HOMA of B-cell function (HOMA-B).

They determined GI and GL using a self-administered diet history questionnaire and evaluated the association between GI, GL, and the incidence of diabetes using Cox proportional hazard modeling.

The authors found that the mean dietary GI was 69.2 (compared with range 48-60 in Western and European countries) and the mean dietary GL (per 1000 kcal) was 87.9.

The study revealed that GI had a significant positive association with the incidence of diabetes. After adjusting for confounders, the hazard ratios (HRs) for diabetes among participants in the fourth and fifth (highest) GI quintiles were significantly increased relative to those in the first (lowest) quintile, at 1.68 and 1.80, respectively.

There was no association between GL levels and diabetes incidence, with nonsignificant HRs of 1.16, 1.56, 1.07, and 1.24 from the second-lowest to highest quintile, relative to the lowest quintile of GI. The researchers also found a significant interaction between GI and HOMA-IR, with the influence of GI on diabetes risk more pronounced at low HOMA-IR; the HR for diabetes associated with highest quintile of GI combined with the lowest tertile of HOMA-IR was 3.67.

The association of GI with diabetes incidence was also affected by HOMA-B, whereby GI in the highest quintile was associated with a significant HR of 1.86 in the lowest tertile of HOMA-B but a nonsignificant HR of 0.93 in the highest HOMA-B tertile.

"Our study indicates that the high prevalence of Type 2 diabetes mellitus in Asian populations may be explained by high-GI diets in people with lower B-cell function," Sakurai and team write.

They add that their findings suggest that a low-GI diet may be beneficial in preventing Type 2 diabetes mellitus in Asian people.

MedWire (www.medwire-news.md) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2011

By Sally Robertson