The study, published in the American Journal of Clinical Nutrition, examined the long term association between MSG consumption and incidence of being overweight in an otherwise healthy population of over ten thousand Chinese adults
The authors, from University of North Carolina, USA, and the Chinese Center for Disease Control and Prevention, China, found that people consuming the highest amount of MSG were associated with a 33 per cent higher risk of weight gain than the group consuming the lowest amount of MSG.
Dr Ka He, a nutrition expert at the University of North Carolina, who led the study, said that although the risk of weight gain attributable to MSG was modest, the implications for public health are substantial because "everybody eats it."
The researchers collected data from the China Health and Nutrition Survey (CHNS), a prospective open-cohort, nationwide health and nutrition survey, consisting of 10,095 apparently healthy Chinese adults aged 18–65 at entry from 1991 to 2006.
He and co-workers reported that men and women who ate the most MSG (an average of 5 grams per day) were around 33 per cent more likely to become overweight by the end of the study than those who ate the least amount of the flavouring (average of less than half a gram per day).
The researchers said this increase was not simply because people were eating more food, some of which happened to have more MSG in, noting that the link between high MSG intake and being overweight held even after accounting for confounding factors including age, physical activity, total energy (calorie) intake, and other major lifestyle factors.
He and colleagues concluded that additional studies are needed “to elucidate mechanisms of action and to establish causal inference.”
MSG is one of the world's most widely used food additives. Though it tends to be more popular in Asian countries, both Europeans and Americans consuming processed foods, such as crisps (chips) and canned soups may have high intakes.
Several studies have examined the potential link between MSG and body weight, with conflicting results. Some scientists have speculated that any increase in weight associated with MSG is due to people consuming larger portions of food with MSG – because it tastes better.
While other research has suggested that the flavour enhancer may influence energy balance by disrupting the hypothalamic signalling cascade – which is known to regulate appetite.
However, World Health Organization (WHO) data, countries with high intakes of the flavour enhancer do not have high population body mass index (BMI).
Source: American Journal of Clinical Nutrition
Volume 93, Issue 6 , Pages 1328-1336, doi: 10.3945/ajcn.110.008870
“Consumption of monosodium glutamate in relation to incidence of overweight in Chinese adults: China Health and Nutrition Survey (CHNS)”
Authors: K. He, S. Du, P. Xun, S. Sharma, H. Wang, F. Zhai, B. Popkin