Researchers from the University of North Carolina recently observed MSG (monosodium glutamate) use in otherwise healthy individuals to investigate a potential connection between those who use the additive and weight gain. They studied 752 Chinese men and women (aged 40-59) randomly chosen from three rural villages in the north and south of China, and found that the number of overweight individuals was significantly higher for MSG users than nonusers. The results of this study were published in the scientific journal Obesity in August 2008.

This is the first human study to look at the link between MSG and weight. Previous studies on MSG and obesity have only been conducted on mice. In those studies, weight gain was significantly greater in MSG-treated mice compared with the control group, even when they were given similar portions of food. A possible explanation for this is that MSG alters the regulatory mechanisms that affect fat metabolism.

What’s MSG?

MSG is the sodium salt of glutamate and is simply made up of glutamate, water and sodium. Glutamate is an amino acid, an important component of protein and peptides. Bound glutamate is not responsible for the flavor property; it’s the free form of glutamate that provides the flavor-enhancing effect in foods.

Contrary to popular belief, MSG is not high in sodium content. According to the International Food Information Council Foundation, MSG only contains 1/3 the amount of sodium as table salt.

Which foods contain MSG?

Natural Foods

Glutamate occurs naturally in almost all foods, including meat, fish, poultry, breast milk, and vegetables. In general, protein-rich foods such as meat and dairy contain large amounts of bound glutamate. On the other hand, vegetables and fruits (especially peas, tomatoes, and potatoes), mushrooms, and certain cheeses (eg. parmesan) usually contain high levels of free glutamate.

Processed Foods

Processed and prepared foods, such as traditional seasonings, stocks, sauces, and canned soups, can contain significant levels of free glutamate, both from natural sources and from added MSG.

Restaurants

Asian restaurants may add MSG to their cooking.

The Bottom Line

It is too early to conclude that MSG use leads to weight gain based on just one study. However, if you are sensitive to MSG, or simply try to avoid it, always check the ingredient list. The FDA requires labeling of all ingredients on processed and packaged foods. When MSG is added to a food, it must be included on the ingredient list, as “monosodium glutamate.” Glutamate-containing food ingredients, such as hydrolyzed protein and autolyzed yeast extract, also must be listed on food labels. Also, if you dine out in an Asian restaurant, simply ask if they prepare foods with MSG. Responsible restaurants will always honor your request to prepare foods without MSG.

Gloria Tsang, RD

Alumni: University of British Columbia – Gloria Tsang is the author of 6 books and the founder of HealthCastle.com, the largest online nutrition network run by registered dietitians. Her work has appeared in major national publications, and she is a regularly featured nutrition expert for media outlets across the country. The Huffington Post named her one of its Top 20 Nutrition Experts on Twitter. Gloria’s articles have appeared on various media such as Reuters, NBC & ABC affiliates, The Chicago Sun-Times, Reader’s Digest Canada, iVillage and USA Today.