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Does Monosodium Glutamate (MSG) Make You Fat?

A couple of years ago I responded to an Ask Dr. Gourmet question about MSG and obesity. This was referring to a study done by researchers in North Carolina who looked at 752 middle-aged Chinese persons, of whom 82% used MSG regularly. They did indeed see a relationship between using MSG and being overweight. Other research has been done on animals, yielding similar results.

The drawback of that study, of course, is that it includes a relatively small population, all from rural villages. The good news is that a much stronger study was recently published in the American Journal of Clinical Nutrition (2011;93(6):1328-36).

This study made use of data gathered through the China Health and Nutrition Survey, which includes people from across China, from high-income and low-income cities as well as suburban and rural areas. The study began collecting data in 1991 and included over 7100 healthy men and women who were between the ages of 18 and 65. In addition to demographic data such as height, weight, education and activity level, the study included detailed information collected about both household and individual food consumption. That consumption was assessed not only by participants recalling what they ate (which is prone to error), but also by actually visiting the participants' homes and performing an inventory of all the food and ingredients there and comparing the changes in that inventory at the beginning and end of the day for three consecutive days.

Further, MSG intake could be directly measured because it is added as an ingredient, just as you might add pepper or another spice. Soy sauce, another common ingredient, contains a known amount of MSG and was also easily weighed.

The average level of daily MSG intake was calculated for each person and correlated with their Body Mass Index. After stratifying average daily MSG intake into five increasing levels, the researchers could see that even after taking into account each person's activity level, the amount of fat or carbohydrates in their diet, and the average total number of calories they consumed each day, those who ate the most MSG were 33% more likely to be overweight than those who ate the least.

What this means for you

We don't know exactly why this association exists, but the current theory is that MSG influences the body's ability to manage its energy balance through interfering with the activity of the hormone leptin in the body. As far as I'm concerned, like High Fructose Corn Syrup, the presence of Monosodium Glutamate in a food should signal to you that it's overly-processed and not something you want to be eating. Better to enhance the flavors of your food by using great quality ingredients - not by adding an artificial flavor enhancer.

First posted: June 15, 2011