White rice, brown rice and the risk of type 2 diabetes: a systematic review and meta-analysis

Abstract

ObjectiveIntake of white rice has been associated with elevated risk for type 2 diabetes (T2D), while studies on brown rice are conflicting. To inform dietary guidance, we synthesised the evidence on white rice and brown rice with T2D risk.DesignSystematic review and meta-analysis.Data sourcesPubMed, EMBASE and Cochrane databases were searched through November 2021.Eligibility criteriaProspective cohort studies of white and brown rice intake on T2D risk (≥1 year), and randomised controlled trials (RCTs) comparing brown rice with white rice on cardiometabolic risk factors (≥2 weeks).Data extraction and synthesisData were extracted by the primary reviewer and two additional reviewers. Meta-analyses were conducted using random-effects models and reporting followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Risk of bias was assessed using the Newcastle Ottawa Scale for prospective cohort studies and the Cochrane Risk of Bias Tool for RCTs. Strength of the meta-evidence was assessed using NutriGrade.ResultsNineteen articles were included: 8 cohort studies providing 18 estimates (white rice: 15 estimates, 25 956 cases, n=5 77 426; brown rice: 3 estimates, 10 507 cases, n=1 97 228) and 11 RCTs (n=1034). In cohort studies, white rice was associated with higher risk of T2D (pooled RR, 1.16; 95% CI: 1.02 to 1.32) comparing extreme categories. At intakes above ~300 g/day, a dose–response was observed (each 158 g/day serving was associated with 13% (11%–15%) higher risk of T2D). Intake of brown rice was associated with lower risk of T2D (pooled RR, 0.89; 95% CI: 0.81 to 0.97) comparing extreme categories. Each 50 g/day serving of brown rice was associated with 13% (6%–20%) lower risk of T2D. Cohort studies were considered to be of good or fair quality. RCTs showed an increase in high-density lipoprotein-cholesterol (0.06 mmol/L; 0.00 to 0.11 mmol/L) in the brown compared with white rice group. No other significant differences in risk factors were observed. The majority of RCTs were found to have some concern for risk of bias. Overall strength of the meta-evidence was moderate for cohort studies and moderate and low for RCTs.ConclusionIntake of white rice was associated with higher risk of T2D, while intake of brown rice was associated with lower risk. Findings from substitution trials on cardiometabolic risk factors were inconsistent.PROSPERO registration numberCRD42020158466.

Trends and Characteristics of Brown Rice Consumption among Adults in Japan: An Analysis of the National Health and Nutrition Surveys, 2012–2019

“…The current findings contribute to the existing literature by confirming that consumers of brown rice exhibit even higher intakes of essential nutrients than those who consume only white rice. These results may be helpful for clarifying the mechanism underlying the association between brown rice intake and a reduced risk of type 2 diabetes [11].…”

Dietary Patterns Associated with Abnormal Glucose Tolerance following Gestational Diabetes Mellitus: The MyNutritype Study

“…Additionally, there appeared to be a linear dose–response relationship for each 50 g/day of white rice or whole grains consumed (RR 1.000316, 95% CI 1.00039–1.000465). In contrast, each 50 g/day increment in brown rice intake reduced the risk of T2D by 13% (RR 0.87, 95% CI 0.80–0.94) [ 58 ]. Nonetheless, white rice, white bread, brown rice, flavoured rice, and local kuih tend to have medium or high glycemic index values.…”

Diet strategies for promoting healthy aging and longevity: An epidemiological perspective

“…Overall evidence suggests that carbohydrate quality plays a more important role in chronic disease outcomes than carbohydrate amount. A series of systematic reviews and meta-analyses of data from large cohort studies have shown that high glycemic index or glycemic load diets (often containing higher amounts of refined grains, such as white rice and white bread, starchy foods such as potatoes, and sugar-sweetened beverages [SSBs]), are consistently associated with increased risk of weight gain, obesity, diabetes, CVD, some cancers, and mortality [60][61][62][63][64], whereas minimally processed grains, legumes, whole fruits, and non-starchy vegetables are protective against these conditions [65][66][67][68]. In a recent longitudinal analysis of changes in carbohydrate intake and long-term weight gain in the NHS and HPFS, increasing dietary glycemic index, glycemic load, and amounts of starch, added sugars, refined grains, and starchy vegetables was associated with greater midlife weight gain.…”