The Fifth Taste

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By Mary Carpenter

“UMAMI foods increase saliva production,” according to Cleveland Clinic HealthEssentials. “Literally they make your mouth water, which improves the way food tastes.”  The taste called umami—based on glutamate, or more familiarly MSG, and other chemical compounds—has recently joined the generally accepted panel of tastes to which humans are sensitive, making five altogether, along with bitter, sweet, salty and sour.

(The umami taste can come from inosinate or guanylate—in meats and plants—as well as from glutamate. MSG, or monosodium glutamate, occurs naturally in vegetables like tomatoes, peas, mushrooms and garlic; and in green tea, soy, seaweed and kimchi.

As the sodium component of L-glutamic acid, MSG is a product of fermenting corn, tapioca and various forms of sugar including sugar cane, sugar beets and molasses. As a flavor-enhancer added during food preparation, MSG also occurs naturally in ingredients, such as yeast and soy extracts, that are used in processed foods like deli meats and canned vegetables.)

Now the previously maligned MSG may be changing its image—based on new evidence that substituting it for table salt creates a salty flavor while reducing overall sodium consumption. In addition, in the decades since fears arose about “MSG attacks”—symptoms that included flushing, headaches and nausea—blinded studies have failed to reproduce the effects.

Detecting each of the five tastes can be important for health and a warning, too: sweet and salty can indicate foods rich in nutrients, while bitter or sour signals poisonous plants or protein-rich food that is rotting. The umami flavor, as it occurs in meats, aged cheeses and seafood, can signal a good source of protein. For tomatoes, the sweet and salty flavor combination comes from high glutamic content —and drying both tomatoes and mushrooms can increase the glutamate.

Among other proposals for a fifth taste sensation are savory (similar to umami), calcium (bitter and chalky), kokumi (heartiness), piquance (spicy), coolness (minty, fresh), metallicity (gold and silver), fat and carbon dioxide (in carbonated soda). “There is no accepted definition of a basic taste,” said Michael Tordoff, a behavioral geneticist at the Monell Chemical Senses Center in Philadelphia. “The rules are changing as we speak.”

Smell, texture and temperature can also affect the taste sensations experienced with different foods. And spicy, while often described as a taste, is technically a pain signal sent by nerves sensitive to touch and temperature — caused by capsaicin in foods seasoned with chili peppers.

Umami-rich, high-protein foods may help curb the appetite because they are more filling. And despite suggested links of umami to higher rates of obesity, no effect of MSG has been found in cells or body parts related to weight gain. Notes Cleveland Clinic dietician Beth Czerwony, “When your food tastes better, you’re inclined to eat more of it.”

The neurotransmitter glutamate plays a role in learning and memory. Variations in availability in the brain, too little or too much, can affect mood, depression and OCD; while excess has been linked to Parkinson’s and Alzheimer’s diseases. But investigators are still working to determine the relative role of receptor sensitivity compared with that of glutamate levels.

MSG contains about 12 percent sodium —2/3 less than that in table salt, which means that substituting MSG for salt in some foods can reduce sodium intake by 25 to 40 percent, according to George Mason University nutritionist Taylor Wallace.  Americans are beginning to understand that “MSG is completely safe,” says Wallace, who predicts “a shift toward using the ingredient as a replacement for some salt to improve health outcomes.”

MSG earned a bad reputation beginning in the late 1960s based on a cluster of reported reactions that became known as MSG symptom complex, most often associated with Chinese food (Asian recipes often include umami, and it is an ingredient in soy sauce.) Czerwony explains that while a small percentage of people may be sensitive to MSG, the effects should disappear in less than an hour.

The FDA now classifies MSG as “generally recognized as safe” (GRAS), its category for food additives determined by experts to be safe—along with the statement that side effects can occur in someone with MSG sensitivity but only after consuming consumed three grams or more of MSG without food. Bacon contains less than 200 mg of glutamate per 100 grams (3.5 ounces), while aged parmesan has about 2,500 mg.

Both taste recognition and sensitivity can diminish with age, with confusion occurring most often among sour, bitter and umami tastes. In a Finnish study at the Functional Foods Forum, those over age 50 and male gender exhibited less sensitivity generally to taste.

Umami-based recipes are popping up everywhere—including from local DC-area umamimami Dyala Madani, whose website urges: “Think Parmesan, braised Beef, Chicken Soup and Shiitake Mushrooms. The deliciousness that is Umami is the flavor that we strive for when we cook and when we eat.”

What I remember from early MSG-attack days is an itchy scalp—maybe what’s called “tingling” in the symptom list —after eating Chinese food. But since learning that MSG is present in almost all processed foods, I realize that the post-Chinese restaurant itchy scalp could have been due more to power of suggestion—or to a coincidental manifestation of my perennially dry skin.

—Mary Carpenter

Every Tuesday in this space, well-being editor Mary Carpenter fills us in on health news we can use.