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

Viswanathan Mohan, Jiayue Yu, Bhavadharini Balaji, Maria Tinajero, Sarah Jarvis, Tauseef Khan, Sudha Vasudevan, Viren Ranawana, Amudha Poobalan, Shilpa Bhupathiraju, Qi Sun, Walter Willett, Frank B Hu, David J A Jenkins, Vasanti S Malik

Journal: BMJ open 2022;12(9):e065426

PMID: 36167362

Free Full Text on HighWire View on PubMed

Plain Language Summary

The prevalence of type 2 diabetes (T2D) has continued to increase worldwide, especially in low-income and middle-income countries. Since rice is a staple food in many cultures and is predominant in most Asian diets, it is hypothesised that improving diet quality by replacing white rice with brown rice could play an important role in the prevention of T2D. The aim of this study was to assess the relationship between rice intake and the risk of T2D. This study is a systematic review and meta-analysis of nineteen studies – 8 cohort studies and 11 randomised controlled trials. Results from the meta-analyses of the cohort studies show a positive association between intake of white rice and risk of T2D. The associations were stronger in women compared with men. Additionally, brown rice was inversely associated with risk of T2D however, the results are based on limited data. Furthermore, the randomised controlled trials showed that the between-group difference in high-density lipoprotein cholesterol was statistically significant in favour of the brown rice group. Authors conclude that replacing white rice with brown rice or other whole grains has the potential to be a low-cost and feasible lifestyle strategy to improve diet quality and help reduce T2D risk.

Abstract

OBJECTIVE

Intake 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.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

PubMed, EMBASE and Cochrane databases were searched through November 2021.

ELIGIBILITY CRITERIA

Prospective 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 SYNTHESIS

Data 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.

RESULTS

Nineteen 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.

CONCLUSION

Intake 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 NUMBER

CRD42020158466.

Address: Department of Biostatistics, Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada.; Women's College Hospital, Toronto, Ontario, Canada.; Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.; Department of Food and Nutrition Research, Madras Diabetes Research Foundation, Chennai, Tamil Nadu, India.; School of Health and Related Research, The University of Sheffield, Sheffield, UK.; Medical Sciences and Nutrition, University of Aberdeen, Aberdeen, UK.; Channing Division of Network Medicine, Brigham and Women's Hospital, Boston, Massachusetts, USA.; Department of Nutrition, Harvard University T H Chan School of Public Health, Boston, Massachusetts, USA.; Risk Factor Modification Centre, St. Michael's Hospital, Toronto, Ontario, Canada.; Department of Diabetology, Madras Diabetes Research Foundation, Chennai, Tamil Nadu, India.; Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada [email protected].

DOI: 10.1136/bmjopen-2022-065426