The incidence of Type 2 diabetes mellitus (T2DM) is rapidly increasing throughout the world, with a current prevalence of over 500 million adults globally. In Japan, approximately 8% of all adults have diabetes. While genetic predisposition, age, and obesity are established risk factors, diet plays a significant role in preventing T2DM.
Among numerous dietary factors, fruit juice combinations have received conflicting attention in research, with some studies suggesting potential benefits while others imply risk. These inconsistencies may stem from variations in genetic predisposition, as fruit juice intake has been recorded in diverse population contexts. To address this, the Japan Multi-Institutional Collaborative Cohort (J-MICC) study aimed to evaluate the association between fruit juice consumption and T2DM in relation to polygenic risk score (PRS) levels.
This cross-sectional study is based on baseline data from the J-MICC study, which was conducted among community-dwelling Japanese adults aged 35 to 69 years between 2005 and 2014. A total of 14,539 participants were initially recruited, from which the final sample consisted of 13,769 participants after eliminating missing data. The frequency of fruit juice consumption was determined by applying a validated food frequency questionnaire, which classified intake as either non-consumption or consumption at least once a week.
A polygenic risk score (PGS002379) estimated the genetic risk of T2DM from 920,930 single-nucleotide polymorphisms (SNPs) and was assessed using groups. The primary outcome was T2DM diagnosed by a physician, which was self-reported. Multivariate logistic regression analyses were used to assess the associations, adjusted for demographic (e.g., age, sex, and education), clinical (e.g., BMI, blood pressure, etc), and lifestyle (e.g., smoking, alcohol consumption) factors.
Among the 13,769 individuals, 814 (5.9%) were reported as having T2DM. The diabetes group was older than the non-diabetic group (59.4 years vs 54.1 years), had a higher proportion of males (67.2% vs. 44.0%), and had a higher average current weight and past average weight at age 20.
The diabetic group also showed less physical activity and more hypertension, dyslipidemia, and a family history of diabetes. There were also significant differences in fruit juice intake: the mean difference in percentage of persons not consuming juice was 64.3% in the diabetic group and 56.3% in the non-diabetic group.
In the entire cohort, regular fruit juice consumption (at least once a week) was inversely associated with T2DM (Model 1: OR 0.77, 95% CI 0.66-0.90) and this difference remained significant following adjustments of potential confounding variables (Model 2: OR 0.77 (95% CI 0.64 to 0.91), Model 3: OR 0.75 (95%CI 0.62 to 0.90)). Dose-response analysis demonstrated that a significant increase in the frequency of fruit juice consumption was associated with progressively decreased odds of T2DM (e.g., 1-2 cups/day: OR 0.47). However, no significant association was observed in participants with low or moderate PRS.
In contrast, among those with high genetic risk (high PRS), the inverse relationship between fruit juice consumption and T2DM was statistically significant. The odds ratio (OR) (95% CI; 0.50-0.93) of T2DM was 0.68 with high genetic risk consuming fruit juice at least once per week versus non-consumers in Model 3. There was also a significant interaction between PRS and juice consumption across the middle-low, middle-high, and high PRS groups.
In the J-MICC study, an inverse correlation was observed between fruit juice consumption and T2DM among patients with a high genetic risk. This may indicate a protective effect of fruit juice in genetically susceptible individuals, which could be attributed to beneficial micronutrients, including flavonoids and vitamin C. The findings are consistent with gene-diet interactions and a precision nutrition model for preventing T2DM. However, the J-MICC study is cross-sectional in nature and relies on self-reported dietary information, making its findings suggestive rather than conclusive. Future longitudinal studies are necessary to establish causality and gain a deeper understanding of the underlying mechanisms.
References: Kawahara T, Nawa N, Oze I, et al. Inverse association between fruit juice consumption and type 2 diabetes among individuals with high genetic risk on type 2 diabetes: The J-MICC Study. Br J Nutr. 2025. doi:10.1017/S0007114525103863
