Low-GI Diet Mirrors Benefits of Fiber and Whole Grain Boost

TOPLINE:

A diet with a low glycemic index (GI) had similar protective effects against diabetes and other chronic diseases as a diet high in fiber and whole grains.

METHODOLOGY:

• A 2019 Lancet report from the World Health Organization promoted fiber and whole grains to manage type 2 diabetes, cardiovascular disease, and cancer but rejected GI as a relevant dietary factor to prevent chronic diseases.
• This meta-analysis assessed the evidence of how GI and glycemic load are associated with four main outcomes and did the same for diets high in fiber and whole grain.
• Researchers identified 10 large prospective cohort studies (each including ≥ 100,000 participants) that assessed associations of GI, glycemic load, and fiber and whole grains with the outcomes of interest.
• The mean age was 56 years, and the mean follow-up duration was 12.6 years.
• The primary outcomes were incidence of type 2 diabetes, cardiovascular diseases and its components, diabetes-related cancers, and all-cause mortality.

TAKEAWAY:

• Compared with low-GI diets, high-GI diets were associated with an increased risk for:
  • Type 2 diabetes (relative risk [RR], 1.27; P < .0001)
  • Total cardiovascular disease (RR, 1.15; P < .0001)
  • Diabetes-related cancers (RR, 1.05; P = .0001)
  • All-cause mortality (RR, 1.08; P < .0001), statistically significant in women only.
• Foods with high glycemic load were associated with an increased risk for incident type 2 diabetes (RR, 1.15; P < .0001) and total cardiovascular disease (RR, 1.15; P < .0001) than foods with a low glycemic load.
• A diet high in fiber and whole grains reduced the risk for all four outcomes, with the association being similar to that observed for low-GI diet.

IN PRACTICE:

“These findings justify the combination of GI with fiber and whole grains in dietary recommendations to reduce the risk of diabetes and related chronic diseases,” the authors commented.

SOURCE:

This study was led by David J.A. Jenkins, MD, Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, Ontario, Canada, and published online in The Lancet Diabetes & Endocrinology.

LIMITATIONS:

The lack of evaluation or absence of positive effects in some analyses may have led to a paucity of reported studies for some outcomes. Moreover, the findings for some outcomes may have had limited robustness because of a small difference in RR. Furthermore, only one or two cohorts were included to compare most disease outcomes related to GI with fiber and wholegrain exposure.

DISCLOSURES:

This study was funded by Banting and Best and the Karuna Foundation. The authors declared receiving research grants, payments, honoraria, and travel support from and having other ties with food and beverage growers, processors and manufacturers, as well as with foundations, chronic disease advocacy and research groups, professional societies, government organizations, and other sources.