Systematic Review and Meta-Analysis of Human Studies to Support a Quantitative Recommendation for Whole Grain Intake in Relation to Type 2 Diabetes

Abstract

BackgroundDue to the increasing evidence of their health benefits, whole grains are recommended for consumption worldwide. Such recommendations are, however, rarely quantitative. Our aim was to perform a quantitative evaluation of the relationship between whole grain consumption and the occurrence of type 2 diabetes (T2D) to support a recommendation on the daily consumption of whole grains.Methods and FindingsWe conducted a systematic review by searching three bibliographic databases. We included human studies addressing the relationship between whole grain consumption and T2D occurrence, and providing quantitative information on daily intake of whole grains. A dose-response meta-regression analysis between whole grain intake and T2D occurrence was performed, using a hierarchical mixed least square linear regression model. Eight observational studies were included (all but one prospective), with a total of 15,573 cases of T2D among 316,051 participants. Quantitative meta-regression demonstrated a significant linear inverse relationship between whole grain intake and T2D occurrence (P<0.0001), with an overall absolute reduction of 0.3% in the T2D rate for each additional 10 g of whole grain ingredient consumed daily. The association persisted when adjusted on sex, age, country, study design, follow up duration, and mode of report of whole grain intakes (as foods or ingredients).ConclusionsThe meta-regression model made it possible to estimate the decrease in T2D risk corresponding to various changes in whole grain intakes, and the results contribute to setting up quantitative recommendations. For instance, consuming three servings of whole grain foods (45 g of whole grain ingredients) daily would induce a 20% relative reduction in the T2D risk as compared to consuming a half serving (7.5 g of whole grain ingredients). These results should be considered for future recommendations, by considering the actual whole grain intake of the concerned populations. The systematic review protocol was published on the PROSPERO register (CRD42013006925).

Consumption of whole grains in relation to mortality from all causes, cardiovascular disease, and diabetes

“…Compared with refined grain products that comprise mainly the endosperm, whole grain foods are rich in a wide variety of nutrients in the outer bran and germ layers: several vitamins, dietary fiber, minerals, and phytochemicals. [1] Many a prospective cohort studies and meta-analyses have linked a higher intake of whole grains and a decreased risk of cardiovascular disease (CVD), [2–4] type 2 diabetes, [5,6] and some types of cancers. [7,8] Human clinical trials have showed that consumption of whole grain foods have beneficial roles in total cholesterol and LDL-cholesterol, [9,10] glucose metabolism, [11] endothelial function, [12] and inflammatory biomarkers.…”

Whole Grain Intake and Mortality From All Causes, Cardiovascular Disease, and Cancer

“…Previous meta-analyses of prospective studies have consistently reported inverse associations between WG intake and type 2 diabetes (T2D), 8–11 cardiovascular diseases (CVD), 8, 12, 13 and certain cancers, 14–16 which are among the major global causes of death. However, existing findings on WG intake and mortality remain largely inconclusive.…”

Health Benefits of Dietary Whole Grains: An Umbrella Review of Meta-analyses

“…Chanson-Rolle et al 2015 8 Aune et al 2013 4 Ye et al 2012 9 increased heterogeneity is inevitable because of the wide variation in study design. Differences in study design include number of participants, duration of the study, age, sex, body mass index, total energy intake for the participants, method of dietary whole grain intake measurements, and source and types of whole grains (eg, whole grain cereals, brown bread, and brown rice).…”