Role of Whole Grain Consumption in Glycaemic Control of Diabetic Patients: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Abstract

Background: Observational studies have indicated beneficial effects of whole grain consumption on human health. However, no evidence based on randomized controlled trials has been established. Our objective was to perform a systematic review and meta-analysis of randomized controlled trials to assess the effects of whole grain consumption in glycaemic control of diabetic patients. Methods: A comprehensive search in four databases (Web of Science, Pubmed, Scopus and Cochrane library) was conducted to collect potential articles which measured the roles of whole grain consumption on glycaemic control up to October 2021. Results: A total of 16 eligible trials involving 1068 subjects were identified to evaluate the pooled effect. The overall results indicated that compared with the control group, whole grain intake presented a significantly reduced concentration in fast plasma glucose (WMD = −0.51mmol/L, 95% CI: −0.73, −0.28; = 88.6%, p < 0.001), a homeostasis model assessment of insulin resistance (WMD = −0.39μU × mol/L2, 95% CI: −0.73, −0.04; = 58.4%, p = 0.014), and glycosylated haemoglobin (WMD = −0.56%, 95% CI: −0.88, −0.25, = 88.5%, p < 0.001), while no significant difference was observed in fast plasma insulin level between groups (SMD = −0.05, 95% CI: −0.25, 0.14; = 40.7%, p = 0.120). In terms of incremental area under the curve (iAUC), data suggested that whole grain effected a significant decrease in Glucose-iAUC (WMD = −233.09 min × mmol/L, 95% CI: −451.62, −14.57; = 96.1%, p < 0.001) and Insulin-iAUC (SMD = −4.80, 95% CI: −8.36, −1.23; = 89.9%, p = 0.002), although only in a small number of studies. Of note, there is evidence for modest unexplained heterogeneity in the present meta-analysis. Conclusion: Whole grain consumption confers a beneficial effect on glucose metabolism in patients with diabetes. Regrettably, since relevant studies were scarce, we failed to provide confident evidence of whole grain consumption on acute effects including Glucose-iAUC and Insulin-iAUC, which should be addressed in further trials.

Associations between dietary fiber intake and cardiovascular risk factors: An umbrella review of meta-analyses of randomized controlled trials

“…Consistent with clinical controlled trials, the beneficial effects of dietary fiber intervention on plasma insulin and circulating SCFA have also been observed by researchers ( 88 , 89 ). However, it should be noted that β-glucan failed to confer a beneficial effect on the improvement of FPI when we performed a subgroup analysis by the type of intervention; the results were consistent with several published meta-analyses ( 51 , 90 ) but contradictory to the meta-analysis conducted by Bao et al ( 91 ). Since meta-analyses evaluating β-glucan for glycemic control were scarce in the current umbrella meta-analysis, we should explain this result with caution.…”

Effects of Diet, Lifestyle, Chrononutrition and Alternative Dietary Interventions on Postprandial Glycemia and Insulin Resistance

“…A cross-sectional study examining the effects of different proportions of carbohydrates at breakfast on postprandial glucose fluctuations in IGT (N = 55) and normal glucose tolerance (NGT) individuals (N = 78), using continuous glucose monitoring, recorded breakfast meals according to the proportion of carbohydrates into low (<45%), medium (45% to 65%) and high carbohydrates (>65%), and reported a gradual increase in postprandial glucose fluctuations with increasing proportions of carbohydrates in breakfast, higher postprandial glucose excursions, higher postprandial glucose spikes, and longer time period in which glucose levels decreased to baseline in subjects with IGT compared to NGT individuals; this study concluded that in IGT a high-carbohydrate meal at breakfast should be avoided and a low carbohydrate meal should be recommended instead [84]. Carbohydrate-rich foods that may be more effective in ameliorating postprandial hyperglycemia and IR include legumes/pulses [85][86][87], whole grains [88][89][90][91], and pasta [92]. In 2017, the American Diabetes Association (ADA) proposed consuming the following foods for preventing T2DM along with weight loss: whole grain cereal products, nuts, yogurt, coffee and tea and limit consumption of red meat and sodas containing sugar [93].…”

Natural nutraceuticals, especially functional foods, their ma-jor bioactive components, formulation, and health benefits for disease prevention - An overview

“…Whole grains consumption supplies high nutrients such as dietary fiber, which when included in, for instance, breakfast can improve the intake of micronutrient and reduce disease risks such as type 2 diabetes mellitus (T2DM), coronary heart disease, etc (Aune et al, 2016;Priebe and McMonagle, 2016;Shahidi, 2009;Williams et al, 2014;Zeng et al, 2018). The regular consumption of whole grains may also lower increased triglyceride levels and LDL (Aune et al, 2016), which helps to tackle diabetes, obesity, and hypertension (Kelly et al, 2017), given the presence of the many bioactive phytochemicals, including phenolic acids, carotenoids, tocopherols, alkylresorcinols, benzoxazinoids, phytosterols, and lignans, as well as many derivatives of cinnamic and benzoic acids, flavonoids, flavanols and flavones (Luthria et al, 2015;Mey et al, 2021;Belobrajdic and Bird, 2013;Xu et al, 2022), some of which are found at the (grain) outer structures, especially the aleurone layers and pericarp seed coat (Zhu and Sang, 2017; Za-A c c e p t e d M a n u s c r i p t bolotneva et al, 2022). Phenolic acids in most grains are concentrated in embryo cell walls and bran, and mostly exist in insoluble bound form, with soluble-conjugated and free forms at minor levels (Mey et al, 2021;Xu et al, 2022).…”

“…Nutraceuticals (also known as bioceuticals) are food products considered as pharmaceutical alternatives with physiological or medicinal benefits (Sarris et al, 2016;Banach et al, 2018;Shahidi, 2012), which help improve body functions, prevent various health conditions, increase life expectancy, maintain body cell integrity, as well as support body structure (Meštrović, 2021;Shahidi, 2012;Yeh et al, 2022). On the other hand, functional foods (and dietary supplements) are among the four major classes of nutraceuticals that provide added value especially towards health promotion and/or disease prevention, mostly formulated by the addition of new components or improving the existing ingredients (Shahidi 2009 andEllis, 2021;Xu et al, 2022). In fact, the term "functional food‖ was first used in Japan in the 1980s, where a government approval process exists for functional foods known as Foods for Specified Health Use (FOSHU) (Alongi and Anese, 2021).…”