Consumption of monosodium glutamate in relation to incidence of overweight in Chinese adults: China Health and Nutrition Survey (CHNS)

Background: It has been hypothesized that monosodium glutamate (MSG), a flavor enhancer, is positively associated with weight gain, which influences energy balance through the disruption of the hypothalamic signaling cascade of leptin action. Objective: The objective was to examine the longitudinal association between MSG consumption and incidence of overweight. Design: Data were collected from the China Health and Nutrition Survey (CHNS), a prospective open-cohort, ongoing nationwide health and nutrition survey, consisting of 10,095 apparently healthy Chinese adults aged 18-65 y at entry from 1991 to 2006. Diet, including MSG and other condiments, was assessed with a weighed food inventory in combination with three 24-h recalls. Incident overweight was defined as a body mass index (BMI; in kg/m(2)) >= 25 or >= 23 based on World Health Organization recommendations for Asian populations. Multilevel mixed-effects models were constructed to estimate change in BMI, and Cox regression models with gamma shared frailty were used to determine the incidence of overweight. Results: The mean follow-up was 5.5 y. The cumulative mean (+/- SD) MSG intake of 2.2 +/- 1.6 g/d was positively associated with BMI after adjustment for potential confounders and cluster effects at different levels (individual, household, and community). The adjusted hazard ratio of overweight was 1.33 (95% CI: 1.01, 1.75; P for trend < 0.01) for participants in the highest quintile of MSG intake compared with those in the lowest quintile after adjustment for age, physical activity, total energy intake, and other major lifestyle factors. Conclusions: MSG consumption was positively, longitudinally associated with overweight development among apparently healthy Chinese adults. Additional studies are needed to elucidate mechanisms of action and to establish causal inference. Am J Clin Nutr 2011;93:1328-36.