Socioeconomic and lifestyle factors modifies the association between nut consumption and metabolic syndrome incidence

Abstract

Background & aims: The aim of this study was to evaluate the association of nut consumption and its various types with metabolic syndrome (MetS) risk and to investigate whether lifestyle factors (physical activity and smoking status) and socioeconomic status (education and occupation) modulate the association of nut consumption and the risk of MetS.

Methods: We prospectively studied 1915 participants of the Tehran Lipid and Glucose study, among whom 591 were diagnosed with MetS during 8.9 years of follow-up. Nut consumption and its various types were assessed using a validated semi-quantitative food frequency questionnaire. Multivariable adjusted Cox regression was used to estimate Hazard Ratios (HRs) for MetS events across tertiles of nut consumption and its various types. Regarding interaction between nut consumption and physical activity levels, education levels, and smoking status on the risk of MetS, using joint classification, the effect modification of lifestyle factors and socioeconomic status on the association between nut consumption (<median and ≥ median) and risk of MetS was assessed by Cox regression.

Results: Nut consumption was inversely associated with MetS risk in multivariable-adjusted models. The highest tertiles of the constituents of nuts including fiber, polyphenol, MUFA and PUFA reduced MetS risk compared with the lowest tertiles, after adjustment for confounders. Among various types of nuts, the multivariable-adjusted HRs of MetS were 0.78 (0.63-0.96) for walnuts, and 0.77 (0.63-0.94) for pistachios, compared with the lowest intake. Among adult population, consuming nuts higher than the median and having moderate to high physical activity levels resulted in significant reduction in the MetS risk (HRs: 0.74, CI: 0.55-0.98 for moderate and HRs: 0.63, CI: 0.47-0.86 for high physical activity level). Participants who did not smoke had lower risk of MetS regardless of their amount of nuts consumption (HRs: 0.67, CI: 0.47-0.94 for intakes < median and HRs: 0.71, CI: 0.53-0.93 for intakes ≥ median). Stratification based on education status resulted in reduction in the risk of MetS in participants consuming nuts ≥ median in both educated and not-educated group (HRs: 0.81, CI: 0.66-0.98 for the non-educated group and HRs: 0.63, CI: 0.47-0.84 for the educated group).

Conclusions: Incorporating nuts, especially walnuts, into dietary patterns reduced the risk of MetS, especially among individuals with more physical activity levels.

Keywords: Lifestyle; Metabolic syndrome; Nuts; Socioeconomic status; Walnut.