HEALTH NEWS

Study Title:

MSG and Obesity Risk in Humans

Study Abstract

Animal studies indicate that monosodium glutamate (MSG) can induce hypothalamic lesions and leptin resistance, possibly influencing energy balance, leading to overweight. This study examines the association between MSG intake and overweight in humans. We conducted a cross-sectional study involving 752 healthy Chinese (48.7% women), aged 40–59 years, randomly sampled from three rural villages in north and south China. The great majority of participants prepared their foods at home, without use of commercially processed foods. Diet was assessed with four in-depth multipass 24-h recalls. Participants were asked to demonstrate MSG amounts added in food preparation. Amounts shaken out were weighed by trained interviewers. Overweight was defined as BMI 25.0 or 23.0 kg/m2(based on World Health Organization recommendations for Asian populations). Eighty-two percent of participants were MSG users. Average intake was 0.33 g/day (s.d. = 0.40). With adjustment for potential confounders including physical activity and total energy intake, MSG intake was positively related to BMI. Prevalence of overweight was significantly higher in MSG users than nonusers. For users in the highest tertile of MSG intake compared to nonusers, the multivariable-adjusted odds ratios of overweight (BMI 23.0 and 25.0) were 2.10 (95% confidence interval, 1.13–3.90, P for trend across four MSG categories = 0.03) and 2.75 (95% confidence interval, 1.28–5.95, P = 0.04). This research provides data that MSG intake may be associated with increased risk of overweight independent of physical activity and total energy intake in humans.

Intro from Obesity Journal website:

Animal studies have suggested a link between the popular food additive monosodium glutamate (MSG) and overweight. Now an analysis conducted by Ka He and colleagues has revealed a correlation in humans. The lack of such research in humans is presumably due to problems quantifying this common additive in commercially processed foods. This study group consisted of rural Chinese adults who primarily prepared their own food without the use of processed ingredients. Because MSG is a popular flavor enhancer in Chinese cuisine, the majority of the study participants added MSG while preparing their meals, making intake calculations for the group more reliable. Independent of confounders such as physical activity and total food intake, MSG was positively associated with overweight in this population, suggesting that MSG may increase one's risk for obesity.

From press release:

People who use monosodium glutamate, or MSG, as a flavor enhancer in their food are more likely than people who don't use it to be overweight or obese even though they have the same amount of physical activity and total calorie intake, according to a University of North Carolina at Chapel Hill School of Public Health study published this month in the journal Obesity.

Researchers at UNC and in China studied more than 750 Chinese men and women, aged between 40 and 59, in three rural villages in north and south China. The majority of study participants prepared their meals at home without commercially processed foods. About 82 percent of the participants used MSG in their food. Those users were divided into three groups, based on the amount of MSG they used. The third who used the most MSG were nearly three times more likely to be overweight than non-users.

"Animal studies have indicated for years that MSG might be associated with weight gain," said Ka He, M.D., assistant professor of nutrition and epidemiology at the UNC School of Public Health. "Ours is the first study to show a link between MSG use and weight in humans."

Because MSG is used as a flavor enhancer in many processed foods, studying its potential effect on humans has been difficult. He and his colleagues chose study participants living in rural Chinese villages because they used very little commercially processed food, but many regularly used MSG in food preparation.

"We found that prevalence of overweight was significantly higher in MSG users than in non-users," He said. "We saw this risk even when we controlled for physical activity, total calorie intake and other possible explanations for the difference in body mass. The positive associations between MSG intake and overweight were consistent with data from animal studies."

As the percentage of overweight and obese people around the world continues to increase, He said, finding clues to the cause could be very important.

"The U.S. Food and Drug Administration and other health organizations around the world have concluded that MSG is safe," He said, "but the question remains is it healthy?"

Co-authors on the study included Liancheng Zhao and colleagues from Fu Wai Hospital and Cardiovascular Institute at the Chinese Academy of Medical Sciences in Beijing. Other researchers on this study were from Northwestern University in Chicago and the INTERMAP Cooperative Research Group.

Study Information

Ka He, Liancheng Zhao, Martha L. Daviglus, Alan R. Dyer, Linda Van Horn, Daniel Garside, Liguang Zhu, Dongshuang Guo, Yangfeng Wu, Beifan Zhou, and Jeremiah Stamler for the INTERMAP Cooperative Research Group.
Association of Monosodium Glutamate Intake With Overweight in Chinese Adults: The INTERMAP Study
Obesity
2008 August
1Department of Nutrition, School of Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.