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

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.

Sugar-Sweetened Beverage and 100% Fruit Juice Consumption on Body Weight in Children and Adults: A Systematic Review and Meta-Analysis

Objectives

Sugar-sweetened beverages (SSBs) have been increasingly linked to the obesity epidemic, however, the evidence on 100% fruit juice and body weight remains controversial. The objective of this research was to synthesize the available evidence on SSBs and 100% fruit juice on body weight in children and adults.

Methods

MEDLINE, EMBASE, and Cochrane were searched through October 11th, 2020 for prospective cohort studies (≥ 6 months) and randomized controlled trials (RCTs) (≥ 2 weeks) assessing the effect of SSBs and 100% fruit juice on BMI and body weight in children and adults. Eligible trials assessed SSBs or 100% fruit juice added to the diet in adults, and reduced from the diet in children against a non-caloric control. Data were pooled using random effects models and presented as b coefficients with 95% CIs for cohort studies and mean differences (MD)s with 95% CIs for RCTs. Results are reported in compliance with the PRISMA guidelines, and the protocol was registered on PROSPERO (ID: CRD42020209915).

Results

Sixty-two articles were identified for SSBs: 40 in children (33 cohorts, 7 RCTs) and 22 in adults (14 cohorts, 8 RCTs), and 22 articles were identified for 100% fruit juice: 13 in children (13 cohorts, 0 RCTs), and 9 studies in adults (3 cohorts, 6 RCTs). Among cohort studies, each serving/day increase in SSB was associated with an increase in BMI in children and body weight in adults (0.06 kg/m2; 95% CI: 0.03, 0.10 and 0.47 kg; 95% CI: 0.24, 0.69, respectively). For 100% fruit juice, each serving/day increase was associated with an increase in body weight in adults (0.19 kg; 95% CI: 0.04, 0.34) while no association was found for children (0.02 kg/m2; 95% CI: −0.01, 0.05). RCTs in children indicated a reduction in BMI gain when SSB consumption was reduced (MD = −0.21 kg/m2; 95% CI: −0.42, 0.00). RCTs in adults indicated an increase in body weight when SSBs were added to the diet (MD = 0.76 kg; 95% CI: 0.51, 1.0), however no effect on weight was found for the addition of 100% fruit juice (MD = 0.08 kg; 95% CI: −0.79, 0.96).

Conclusions

SSB consumption promotes weight gain in both children and adults. Evidence from cohort studies indicate a positive association between 100% fruit juice and weight gain in adults and a marginal association among children. Findings from RCTs on 100% fruit juice in adults showed no effect, and there is a need for trials among children.

Funding Sources

None.

Plant-Based Dietary Patterns and Cardiometabolic Risk: A Systematic Review and Meta-Analysis of Prospective Cohort Studies

Objectives

Plant-based diets defined by limited animal food consumption have been extensively associated with cardiometabolic health benefits in Western nations. Diet indices are increasingly used to distinguish the protective characteristics of a plant-based diet at different levels of adherence. We aimed to synthesize evidence on the association between adherence to plant-based diet indices and cardiometabolic risk. A plant-based diet index (PDI) is hypothesized to be inversely associated with type 2 diabetes (T2D) and cardiovascular disease (CVD) with a stronger association with the healthful index (hPDI) that emphasizes higher quality plant-based foods.

Methods

We systematically searched MEDLINE, EMBASE and CINAHL databases through January 2021. Prospective cohort studies assessing the association of plant-based diet indices with T2D and CVD in adults were included and appraised for risk of bias and quality (NutriGrade). We followed the PRISMA-P, Cochrane and MOOSE guidelines. Random and fixed-effects meta-analyses were conducted to pool risk ratios (RR) of extreme quantiles. Dose-response meta-analyses were conducted after harmonizing all diet index scores. I2-values of 30–60%, 50–90%, and 75–100% denoted moderate, substantial, and considerable heterogeneity respectively.

Results

We included a total of 10 studies from 5927 retrievals. Across 6 studies there were 22 135 cases of T2D over 4 817 308 person-years. Across 7 studies there were 15 077 cases of CVD over 6 117 016 person-years. The PDI was associated with a lower risk of T2D (RR = 0.82, 95% CI [0.75, 0.91], I2 = 55.4%), and CVD (RR = 0.88, 95% CI [0.8, 0.96], I2 = 16.2%). The hPDI had a stronger inverse association with T2D (RR = 0.73, 95% CI [0.68, 0.77], I2 = 84.3%) and CVD (RR = 0.8, 95% CI [0.77, 0.88], I2 = 55.9%). All dose-response relationships were linear (except hPDI with CVD). All studies had acceptable risk of bias and the quality of evidence was moderate.

Conclusions

Adherence to a plant-based diet was inversely associated with T2D and CVD with a stronger association for a healthful plant-based diet pattern. Since highest quantiles of the index still included moderate meat consumption, linear dose-responses emphasized potential benefits on risk of T2D and CVD with any incremental progression towards a plant-based diet.

Funding Sources

Nora Martin Fellowship, Ontario Graduate Scholarship.

Effect of Maternal Vitamin D Supplementation on Iron Status During Pregnancy

Objectives

Vitamin D may have an adjunctive role in the prevention and treatment of iron deficiency (ID) through its proposed role in the regulation of erythropoiesis and circulating hepcidin concentrations. Observational studies have shown associations between low vitamin D and iron status; however, there are few data from intervention trials. In participants of the Maternal Vitamin D for Infant Growth Trial (MDIG; NCT01924013), among whom the baseline prevalence of vitamin D deficiency was 64%, we examined the effect of prenatal vitamin D supplementation on iron status during pregnancy by testing the effect of vitamin D supplementation on serum ferritin concentrations.

Methods

In this double-blind, dose-response, randomized trial in Dhaka, Bangladesh, women were recruited at 17–24 weeks’ gestation and randomly assigned to receive a prenatal vitamin D3 dose of 4200, 16,800, 28,000 IU/week or placebo. Serum ferritin was quantified using an electro-chemiluminescence immunoassay. Plasma C-reactive protein (CRP) was analysed by enzyme-linked immunoassay. Linear regression was used to test the hypothesized effect of vitamin D supplementation on serum ferritin (n = 1011 of 1300 enrolled). In a sensitivity analysis, we adjusted for concurrent CRP to correct for inflammation (n = 920). Regression correction was used to generate an inflammation-corrected estimate of the prevalence of ID (n = 920).

Results

Prevalence of ID (serum ferritin <15 µg/L) was high overall (27% corrected for inflammation; 12% uncorrected). Geometric mean (95% confidence interval) serum ferritin concentrations were lower in each of the vitamin D supplementation groups [43.1 (38.1, 48.7), 44.8 (40.4, 49.7) and 45.1 (41.5, 49.1) µg/L in the 4200, 16,800 and 28,000 IU/week groups, respectively] compared to the placebo group [50.3 µg/L (45.0, 56.2)], although none of the pairwise differences between each vitamin D group and placebo were statistically significant at the P < 0.05 threshold. Adjusting for CRP did not change the inferences.

Conclusions

In a population with concurrently high prevalence rates of iron and vitamin D deficiency, prenatal vitamin D supplementation did not lead to improvements in iron status by late gestation. The possibility of a negative effect of vitamin D supplementation on iron status should be further explored.

Funding Sources

The Bill and Melinda Gates Foundation.