What is MSG? (Part I: MSG, Flavor Enhancers, and Glutamates)

We know MSG is a food additive, but what IS it exactly? And, are glutamates, yeast extract, and natural flavors just fancy terms for MSG?

So, what is MSG? MSG (monosodium glutamate) is a flavor enhancer added to foods, especially some Asian foods as well as broths, soups, gravy, sauces, and many snack foods.

MSG gives foods a unique savory or “meaty” taste, known as umami.

According to the FDA, most MSG is created through fermentation of starch, sugar beets, sugar cane, or molasses. However, it can also occur naturally in some foods, such as tomatoes and cheese.

A Brief History of MSG

According to the Science Friday website, in 1908 a Japanese chemist extracted MSG from seaweed and discovered its ability to enhance flavor. After that, it found its way into processed foods across the world.

In the 1960s, a scientist wrote a letter to The New England Journal of Medicine reporting his own experience with “Chinese Restaurant Syndrome.” Over the next few decades, the controversy about MSG grew.

With today’s focus on food quality and health, people have become more discerning about what’s in their food. Debate still exists over MSG’s safety: as with vegetable oils, mainstream medicine claims it’s safe, while alternative medicine experts tend to demonize it.

Also, many claim that MSG gives them adverse side effects, such as headache or face flushing. There’s even debate around whether such reactions are “real,” i.e. caused by MSG or by something else.

In my experience, most people don’t understand what MSG is and how it differs from other flavor enhancers such as yeast extract and “natural flavors.”

The Rogue Scientist Investigates

Somewhere in all this MSG debate resides the truth. Or at least a bunch of useful facts.

I decided to go looking for both.

I wrote a two-part series on MSG and, because MSG’s flavor-enhancing cousins (such as yeast extract) have caused confusion as well, I included them too.

This article (Part I) discusses MSG and other flavor enhancers, and defines certain terms that tend to create misunderstanding. Part II will explore whether MSG and other flavor enhancers are safe to eat, as well as delve into MSG “sensitivity” (is it real or just an easy scapegoat?).  

Defining Key Terms: MSG, Glutamate, Glutamic Acid, and Glutamine

Part of the confusion around MSG and other flavor enhancers revolves around terminology. Which makes sense — if you haven’t taken biology, chemistry, and biochemistry, how all this works can be difficult to understand if it isn’t explained well.

If you want to understand MSG, its safety, and how it impacts you, you’ll need to know a few basics.

MSG (Monosodium Glutamate)

In chemical terms, MSG is a salt (it’s actually white and crystalline like you see in the image above). To make MSG, a single sodium ion combines with glutamate.

If a flavor enhancer doesn’t have the chemical structure of glutamate combined with a sodium ion, it’s not MSG.

Again, most MSG gets created through a fermentation process, but it does occur naturally in some foods. This is why some food labels will state “No added MSG.”

Glutamate and Glutamic Acid

Glutamate is the ionic (charged) form of glutamic acid, which is an amino acid. Glutamate is basically glutamic acid that’s lost a hydrogen atom, and you’ll find that these two terms are often used interchangeably.

Glutamate acts as an excitatory neurotransmitter (it makes your neurons fire) and is the most abundant excitatory neurotransmitter in the brain.

Glutamic acid is a non-essential amino acid found in humans and other animals. Amino acids are the building blocks of protein, and non-essential means your body can manufacture it. It occurs naturally in many foods containing lots of protein, like meat, fish, poultry, and eggs, although it occurs in lots of other foods as well.

However, in these foods, glutamic acid is “bound” (attached to other amino acids to create the protein), and therefore lacks the flavor-enhancing piece.

For umami flavor, the glutamic acid must be unbound (“free”) — i.e. glutamate. Free glutamates are either created (like MSG) or they occur naturally in foods such as cheese, soy sauce, tomatoes, and parmesan cheese.


Glutamine is another non-essential amino acid. It doesn’t relate to MSG or flavor enhancement, but I included it here because glutamine sounds similar to glutamate, which can cause confusion.

Now that you understand these terms, let’s move on to discuss the other flavor enhancers.

Yeast Extract and Other Flavor Enhancers

MSG is not the only flavor enhancer in town. If you go to your cupboard or fridge and check your ingredients, you’ll find other flavor enhancers in soup stock/broth, many types of sauces, flavored potato chips and snacks, and other packaged or canned foods.

Let’s take a look at these other flavor enhancers:

Yeast Extract

This flavor enhancer offers umami flavor like MSG does. It’s made from yeast, usually brewers or baker’s yeast, where the cell wall is ruptured and its contents used to create the flavoring. Yeast extract does contain glutamate, but not as much as MSG does.

Yeast extract comes in two types: autolyzed and hydrolyzed. Both involve enzymes breaking down the yeast cell proteins (this is what brings the flavor), but one uses enzymes already present in the yeast cell while the other uses outside enzymes.

Interestingly, unlike MSG, which enhances flavor but has no flavor itself, yeast extract actually has flavor. So much so that it’s used as a spread in the UK and Australia, known as Marmite or Vegemite.

Hydrolyzed Proteins

Hydrolysis is the term for breaking chemical bonds with water. Essentially, hydrolyzed proteins are proteins that have been broken down into smaller parts.

Hydrolyzed proteins come from vegetable or animal sources such as soy and whey, hence the “hydrolyzed soy protein” you see in your ingredient list. The ingredients must identify the source of the hydrolyzed protein (i.e. soy, whey, etc.).

Hydrolyzed proteins release glutamate, and when these hydrolyzed proteins combine with salt in food, they create MSG (and therefore flavor). Essentially, they offer a way to flavor-enhance foods without adding MSG itself.

Interestingly, some groups promote consumption of hydrolyzed proteins, including bodybuilders and those focused on digestive/malabsorption problems. Why? These broken-down proteins are easier to digest and absorb.

Disodium Guanylate and Disodium Inosinate

Disodium Guanylate and Disodium Inosinate are flavor enhancers derived from nucleotides, the same class of compound that comprises DNA. The two enhance each other, so if you find one on your ingredient list, you’ll typically find the other.

Neither disodium guanylate or inosinate have glutamate. Instead, food producers may combine these with a glutamate flavor enhancer to get even stronger umami flavors. Or, they get added to foods naturally high in glutamates such as tomatoes and parmesan cheese.

Natural Flavor

This class of flavor enhancer really requires its own article, which you can find here. That’s how broad this topic is. However, because natural flavor is important to this discussion, I will offer a brief description here.

In a nutshell, natural flavors are flavorings extracted from natural sources, whether animal, plant, or yeast. This contrasts “artificial flavors,” which are NOT derived from natural sources. See this FDA page for details and definitions.

The problem with natural flavors is they vary a LOT depending on the product. The composition of natural flavors in sausage will differ greatly from those in fruity candy, for example.

The tricky part? The manufacturer doesn’t have to reveal what’s in them, so we know almost nothing about what we’re consuming other than it originated from a natural source.

Because we don’t know the specific composition of these flavorings, they may or may not contain glutamates or other substances that cause adverse reactions in some people.

Is Yeast Extract or “Natural Flavor” Just MSG by Another Name?

I see this topic come up from time to time in the health groups I belong to. Some websites even claim that yes, yeast extract, natural flavors, and the other flavor enhancers I discuss above are just “hidden forms of MSG.”

They’re wrong.

Chemically, yeast extract and the rest of those flavor enhancers are not MSG.

Having said that, many of these flavor enhancers do contain glutamates and may have similar effects as MSG.

Which leads to the next logical question:

Are MSG and these other compounds safe to eat?

And: Why do some people report bad reactions to MSG while others have zero problem with it?

I’ll discuss both of these in Part II.

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Related Articles That Might Interest You

MSG, Part II: Is MSG Bad for You?

What is Natural Flavor? 6 Facts You Need to Know

The Rogue Scientist

Christie Hartman is a writer and scientist specializing in science-based health. A biology major as an undergrad, she completed her PhD in behavioral genetics at the University of Colorado Boulder. Before starting her writing career, she worked as a scientist and professor at CU’s School of Medicine, where she studied the genetic contributions to substance abuse and antisocial behavior.

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