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
which combined one molecule of glutamate with the ion sodium - to make it more tasty.
This umami seasoning is still widely used today, and is 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 normal metabolism, 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 MSG, glutamate is 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.
In the stomach, there are more glutamate receptors, and these activate the vagus nerve.
The vagus nerve notifies the brain that protein-rich foods have entered the stomach, and then the
brain tells the stomach and intestines to prepare for protein digestion.
After leaving the stomach, glutamate enters the small intestine where over 95% 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.
Now, 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 bound, or in other words it’s attached to other amino
acids in the form of a protein, or 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 2240mg, marmite has 1960mg, and fish sauce has 1383mg.
More common foods include parmesan cheese which has 1680mg, soy sauce which has 1264mg,
and oysters sauce which has 900mg.
Some foods that may surprise you include walnuts which have 658mg and tomatoes which have 246mg.
Breast milk is also high in free glutamate with its content varying by lactation stage
and highest in mature milk.
In fact, a breast-fed infants consume more free glutamate per pound of body weight, than
an adult.
Overall, less than 10 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 United Nations Food and Agriculture Organization, the World
Health Organization, and the US 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.
Which is why it’s recommended that we limit 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, something 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 glutamate content of foods while decreasing salt in a recipe
can reduce the overall sodium content by up to 40%.
Okay - as a quick 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 every
day foods.
Extensive research has shown that MSG is safe to consume, doesn’t cause headaches and
could be a helpful tool for lowering the amount of sodium people eat.