Nutrition 101 Video Series: Monosodium glutamate (MSG)

Nutrition 101 Video Series: Monosodium glutamate (MSG)

This is the seventh installment of our “Nutrition 101” video series, presented in partnership with Osmosis, a group that focuses on health science education, highlighting the basics of several nutrition topics. For a look back at what we’ve covered so far, watch our videos on  fats,  carbohydrates and sugars,  hydration, low-calorie sweeteners, protein and gut health.

Savory foods are inherently delicious—but have you ever wondered why? In 1908, a Japanese professor pondered this question when exploring what made kelp broth taste so good. He recognized a unique taste in it that was different from the four well-known tastes of sweet, sour, bitter and salty. It turns out that glutamate, an amino acid made by many plants and animals, was the source of this distinctive taste, which became known as “umami” in reference to “umai,” the Japanese word for delicious. The professor isolated glutamate from seaweed to produce a crystallized salt form of glutamate that combined one molecule of glutamate with the ion sodium to make it even tastier. This umami seasoning is still widely used today and is also known as monosodium glutamate, or MSG.

Glutamate is the most abundant amino acid found in nature, and it’s one of the 20 amino acids that make up proteins in the human body. Because glutamate is synthesized as part of the normal metabolic process, it is considered a non-essential amino acid. In other words, we don’t technically need to get it from food. Our bodies synthesize about 50 grams of glutamate each day and store about 4.5 pounds of glutamate in major organs like the brain, muscles, kidneys and liver. On average we eat about 10 to 20 grams of glutamate each day, mostly from protein-containing foods like meat, cheese, nuts and legumes.

Whether consumed from food or in the form of MSG, free glutamate is detected by umami receptors and metabolized in the same way. In the saliva in the mouth, MSG separates into its original two parts—glutamate and sodium—and then glutamate binds to its receptors to elicit an umami, or savory, flavor sensation. Then, in the stomach, more glutamate receptors activate the vagus nerve, which notifies the brain that protein-rich foods have entered the stomach. The brain then tells the stomach and intestines to prepare for protein digestion.

After leaving the stomach, glutamate enters the small intestine, where over 95 percent of the glutamate ingested is used as fuel by enterocytes, the epithelial cells of the gastrointestinal tract. The rest is absorbed into the bloodstream and delivered to cells to be used for metabolism or to make proteins.

It turns out that glutamate is also synthesized by the brain, where it acts as a neurotransmitter. Some people have speculated that MSG may enter the brain and even trigger migraine headaches. However, the glutamate we eat doesn’t affect the amount of glutamate in our brain. This is because the glutamate we get from food is almost entirely utilized during its journey through the gastrointestinal tract. The blood-brain barrier prevents the small amount of glutamate in our bloodstream from entering the brain. Based on this aspect of human physiology and confirmation in recent scientific reviews, the International Classification of Headache Disorders removed MSG from its list of headache triggers in 2018.

Within food, glutamate is either boundattached to other amino acids in the form of a proteinor free by itself. The more free glutamate there is, the more umami flavor a food will have. Processes like aging or ripening will increase the amount of free glutamate in a food. Take a deep red glossy tomato for example—it will have more free glutamate than a firm pale one. Similarly, a cured ham will have more free glutamate than fresh pork. Seasoning a food with MSG also increases free glutamate.

Some foods are very high in free glutamate. In 100 grams, Kombu seaweed has 2,240 milligrams (mg); Marmite has 1,960 mg; and fish sauce has 1,383 mg. More common foods include parmesan cheese, which has 1,680 mg; soy sauce, which has 1,264 mg; and oyster sauce, which has 900 mg. Some free-glutamate-containing foods that may surprise you include walnuts, which have 658 mg, and tomatoes, which have 246 mg. Breast milk is also high in free glutamate, with its content varying by lactation stage and at its highest in mature milk. In fact, on average, breast-fed infants consume more free glutamate per pound of body weight than adults.

Overall, less than ten percent of the glutamate we consume is in the form of umami seasoning, or MSG. After decades of research, MSG is considered safe by scientists and regulatory authorities around the world, including the United Nations Food and Agriculture Organization, the World Health Organization, and the U.S. Food and Drug Administration.

In fact, MSG has been recognized as a tool to help people eat less salt, or sodium chloride. Consistently eating too much sodium can increase blood pressure and may lead to hypertension, a top risk factor for cardiovascular disease. That’s why it’s recommended that we limit our sodium intake to less than 2,300 mg per day. But lower-sodium foods aren’t appealing to everyone, which makes this recommendation a tough one to meet. MSG has the potential to help with this, an observation noted in the 2019 Dietary Reference Intake report for sodium from the National Academies of Science, Engineering and Medicine. Not only does MSG add flavor, but despite having sodium in its name, MSG contains three times less sodium by weight than table salt. For example, increasing the glutamate content of a food while decreasing salt in a recipe can reduce the overall sodium content by up to 40 percent.

To recap, glutamate is the amino acid responsible for the flavor of umami and plays an important role in digestion by signaling for protein digestion and fueling the cells of the GI tract. Our bodies make glutamate, and it’s also present in a variety of whole foods. Glutamate can also be added by seasoning foods with MSG. In the saliva in the mouth, MSG separates into glutamate and sodium, which is why the body doesn’t differentiate between the glutamate in umami seasoning and the glutamate in everyday foods. Extensive research has shown that MSG is safe to consume, doesn’t cause headaches, and could be a helpful tool for lowering the overall amount of sodium people eat.

YouTube video

This video was partially supported by a grant from Ajinomoto Health & Nutrition North America, Inc.