There are numerous flaws and inaccuracies in a recent study (He et al. AJCN, April 2011) which make the suggestion of a relationship between MSG and weight gain not only inappropriate but implausible. Furthermore, the authors' proposal of a possible mechanism for the link ignores the understanding of glutamate and its metabolism, built on more than a hundred years of science.
Glutamate contributed by MSG seasoning is just a small percentage of the glutamate consumed every day as part of a normal, healthy diet. This is the case even in countries where MSG is used widely to season home-made food.
Monosodium glutamate is the salt of an amino acid - one of the most abundant amino acids in our diet. Amino acids are the building blocks for proteins, whether in our bodies or in our food. Glutamate is found in food either 'bound' into protein or as 'free' glutamate. 'Bound' glutamate becomes 'free' as proteins break down - when meat or cheeses are aged, for example, or when food proteins are digested.
Significant levels of 'free glutamate' occur in many of the foods we consider tasty and delicious.
The table below lists the glutamate content of some common foods:
| Food |
Free glutamate (mg) |
Bound glutamate |
| Cow’s milk (1 cup) 1 |
4.5 |
1856 |
| Human breast milk (1 cup) 1 |
50 |
519 |
| Parmesan cheese (2 oz.) 1 |
680 |
5579 |
| Peas (1/2 cup) 1 |
227 |
6326 |
| Tomato juice (1 cup) 2 |
827 |
Not available |
| Mushrooms 2 |
188 |
Not available |
| MSG flavour enhancer (1/4 tsp) 3 |
1000 |
0 | |
Sources: 1Institute of Food Technologists (cited by IFIC), 2FDA (cited by IFIC,) and 3Ajinomoto.
The glutamate from MSG seasonings and the glutamate from other foods is treated by our bodies in exactly the same way. Most of the glutamate we consume, whether naturally occurring in food or as seasoning, does not enter the bloodstream - it is used by the cells lining the digestive tract for energy.
Our bodies also make glutamate as part of normal metabolism, and our major organs store glutamate. There is about 10g of free glutamate in our bodies, of which 6g is stored in our muscles.
Despite the appeal of a 'silver bullet', it is highly unlikely that a single ingredient, especially one which has been part of the diet for many decades, is the cause of obesity. Diverting attention from proven contributors to overweight and obesity, such as eating too much and getting too little exercise, is not in the public interest.
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