Filtering the facts on flavor enhancers

As early as March of 1994, the U.S. Food and Drug Administration may rule to require the phrase "contains glutamate" to appear on product labels following ingredients such as yeast extracts and certain hydrolyzed proteins. A motivating factor behind this ruling is an extension of the public outcry over the flavor enhancer monosodium glutamate (MSG). In particular, anti-MSG advocates claim that yeast extracts, hydrolyzed proteins and other such ingredients are used by food manufacturers to willfully "hide" added MSG in food products.

The potential effects of this ruling go beyond MSG and other flavor ingredients because glutamate is naturally occurring in many foods.

Consequently, the FDA's eventual decision can have great impact on the food industry and, consequently, food product designers. This feature will examine the history of glutamate use as well as the events that shaped the controversy, and will offer a review of information to help product design teams sort out the issue for their company.

Nature of the beast

In the eyes of the FDA, the term "glutamate" refers to all the salts and free forms of glutamic acid. Glutamic acid is an amino acid that is present to some degree as a component of all proteins and, subsequently, many foods. It can be found either bound with other amino acids in peptides and proteins, or in a free form. Dr. Karl Ritthausen, a German scientist, first identified glutamic acid in 1866. Although not recognized by Ritthausen, the L-configuration of free glutamic acid exhibits flavor enhancing properties.

Monosodium glutamate is the readily soluble sodium salt of glutamic acid. In 1908, Dr. Kikunae Ikeda isolated MSG from seaweed and discovered its flavor contributions. Currently produced through fermentation, consumers and industry worldwide use MSG as a flavor enhancing ingredient.

How glutamic acid functions in this capacity remains somewhat of a mystery. Part of this mystery stems from the fact that the definition of a flavor enhancer is somewhat murky. Many industry resources point to the definition for flavor potentiators as stated by Gary Reineccius, Ph.D., of the University of Minnesota's Department of Food Science and Nutrition in St. Paul: "Flavor potentiators are compounds which have no flavor of their own at usage levels but yet intensify or enhance the flavor of a food."

But many in the industry believe this doesn't say it all.

"I also add that it tends to round out the flavor of the food," says Robert Patti, vice president of savory ingredients for Gist-brocades Food Ingredients Inc., Brookfield, WI. "You may not be enhancing, but you take something that is sharp or bitter and round it out."

Another contributing factor for why flavor enhancement isn't well understood is that flavor perception itself is still the subject of much ongoing research. Nevertheless, various researchers have proposed several theories of how flavor enhancers might work. These can be divided into two categories: those that treat enhancers as flavor potentiators only, and those that treat flavor-enhancing ingredients as flavor contributors.

Most potentiation theories focus on how enhancers interact with taste receptors. For example, one theory is that MSG and other enhancing substances actually make more receptor sites available to flavor compounds. Other researchers have proposed that potentiators interact with proteins at the receptor sites to improve the environment for taste receptor stimulation. Still, other researchers postulate that potentiators somehow strengthen the synaptic signal from the receptor site to the brain.

One theory expands the idea of enhancer/receptor interaction to include some sort of interaction between the enhancer, the receptor and the flavoring material itself. This theory, proposed by Tilak Nagadowithana, director of research for Red Star Specialty Products in Milwaukee, states that MSG binds in some way with both the taste receptor and the flavor material. This, in effect, momentarily locks the flavor more solidly to the receptor and, subsequently, boosts the signal.

"That is key," says Nagadowithana. "In other theories, there is no connection between the MSG and the savory material. There actually is some bonding in there."

This mechanism would explain the specificity of MSG's effect. It also helps to explain the synergism between MSG and ribonucleotides. Nagadowithana proposes that, like MSG, nucleotides also bind to both the savory flavor compounds and receptors. When used with MSG, the two work together holding the flavor substance even tighter to the taste receptor, yielding the synergistic potentiation effect.

Function for flavor

Other research indicates that glutamate doesn't enhance any of the four traditional basic tastes -- sweet, sour, salty and bitter -- because it possesses its own unique flavor known as "umami." Such research relies on multi-dimensional scaling experiments that arrange taste stimuli into a map based on the similarity of their taste properties. When mapped, the taste properties of umami-producing substances fall outside the region of the map occupied by the classic tastes. The conclusion follows that not only does MSG not enhance any of the four classic tastes, but umami cannot be formed by a combination of classic tastes.

Confirming this work are experiments on animal subjects wherein taste receptors are stimulated electrically. In some cases, research has even postulated the presence of specific umami taste receptors.

With the acceptance of umami as a basic taste, glutamate becomes a flavoring component. Does this mean that it can still act as an enhancer as well?

"Yes, but I think any flavor does," says Patti. "It becomes a gray area after you leave the strict definition. It's common in the industry to use flavors as enhancers."

One example of this might be using a sweet flavor to create a mild beef profile or adding a beef flavor to a chicken soup to increase the dark notes. In such cases, it would be difficult to draw the line between flavor and flavor enhancer.

Other research serves to make MSG's exact function even more difficult to pin down because it suggests more of a tactile effect in the mouth. Such research has been conducted by Mike Hudson, Ph.D., supervisor of food applications and technical services for Provesta Corp., Bartlesville, OK, using a descriptive flavor analysis panel. In the test, panelists were trained to look for aromatics, the four basic tastes and chemical feeling factors in various flavor-enhancing ingredients. They found that MSG, while having very low scores for basic taste and aromatics, scored the highest on feeling factors.

The troubles begin

In spite of the challenges inherent in defining exactly what MSG does, applied research demonstrated its efficacy in improving the flavor of foods. By its very nature, food processing often robs food of organoleptic properties. Here, then, was a readily soluble component of protein that boosts the remaining flavor profile. It would seem perfect.

Perfect, that is, until 1968, when Dr. Ho Man Kwok, a physician, detailed his personal MSG sensitivity experience in a letter to the New England Journal of Medicine.

"The syndrome, which usually begins 15 or 20 minutes after I have eaten the first dish, lasts for two hours without any hangover effect," wrote Kwok. "The most prominent symptoms are numbness at the back of the neck, gradually radiating to both arms and the back, and general weakness and palpitation."

A volley of skeptical letters followed, including one from Dr. Herbert Schaumburg of the Albert Einstein School of Medicine. In 1969, Schaumburg set out to disprove the existence of the syndrome. Later that year, however, he published his findings in Science and concluded that MSG could produce such undesirable effects after all.

In that same publication in the same year, Dr. John Olney, Washington University, revealed that injecting or force-feeding MSG to rodents induces brain damage and other toxic effects. Subsequent research indicated that MSG actually produced brain lesions.

In light of such information, it might seem surprising that the FDA didn't seek to ban MSG immediately. The agency, however, is required to base such decisions on a consensus of valid, accurate scientific data. At this point, the information presented fell into three general fault categories that kept it from meeting this criteria.

Anecdotal reports, such as Kwok's original letter are common in the MSG issue. As unfortunate as negative reactions may be for some people, the FDA cannot use these to specifically link such reactions to MSG. Achieving a solid scientific consensus requires the use of controlled studies. Naturally, these have problems of their own:

Controlled, double-blind challenges have repeatedly shown MSG not to be a problem for the vast majority of those who claim sensitivity. This has been the case since the first such study was conducted in 1972 by Richard Kenney, Ph.D., of George Washington University Medical Center, Washington, D.C.

Further rodent research has confirmed that nervous system damage requires dosages of more than 4 grams per kilogram of body weight administered either through force feeding or injection. (This translates into more than half a pound of MSG for a 150-pound human.) In primates, several studies have demonstrated no central nervous system damage at similar dosages following force feeding, subcutaneous injection or dietary administration.

FDA's evaluation of MSG didn't stop there. MSG has, in fact, been part of an ongoing project started in 1970, wherein the agency reviews the safety data of all ingredients listed as "Generally Recognized As Safe" (GRAS), according to the 1958 Food Additives Amendment to the Federal Food, Drug and Cosmetic Act.

As part of this review, an independent body of scientists -- the Select Committee on GRAS Substances of the Federation of American Societies for Experimental Biology (FASEB) -- concluded in 1980 that MSG is safe at current use levels, but that safety at significantly increased levels required additional evaluation.

FDA's Advisory Committee on Hypersensitivity to Food Constituents also reviewed MSG and in 1986 concluded that it posed no threat to the general public, but that reactions might occur in a small percentage of the population (between 1 and 2% versus up to 25% as stated by questionnaire-type studies). This position was later reinforced by a report from the FDA Center for Food Safety and Applied Nutrition's Adverse Reaction Monitoring System (ARMS).

The 1990 ARMS report found that a small percentage of individuals have moderate reactions, such as skin flushing, tightening of jaw and upper chest muscles, and headaches shortly after eating food containing MSG. The report documented no severe reactions, but one investigator reported aggravation of asthma in some individuals. This particular testing, though, lacked credibility on two levels. First, the challenge to the test subjects was not double-blind. Second, the researcher observed the onset of the reaction to be up to several hours after ingestion. The turnover of free glutamic acid in the human body is too rapid to support such a delayed effect. Research also has ruled out that this effect was caused by elevated glutamic acid in the blood plasma because MSG has not elevated these levels in controlled studies.

Consequently, the FDA maintained that current labeling of MSG was adequate in protecting human health. The agency is certainly not alone in this evaluation. Glutamate also has been judged safe by the Joint FAO/WHO Expert Committee of Food Additives, the Scientific Committee for Food of the Commission of the European Communities, the Council on Scientific Affairs of the American Medical Association and the Expert Panel on Food Safety and Nutrition.

People power persists

In spite of such findings and reports, word of mouth still spreads a negative message about MSG. Concerns have particularly grown in the last five to 10 years following the publication of the book, In Bad Taste: the MSG Syndrome, by Dr. George Schwartz (Health Press, Santa Fe, NM, 1988.) The book traces the problems of MSG using the research of Schaumburg and Olney, as well as a number of case histories.

Many consumers – who don't usually apply the restrictions of scientific consensus – found solace in Schwartz's work. Others became quite angry over the seeming lack of government action and decided to speak out.

In 1990, the National Organization Mobilized to Stop Glutamate (NOMSG) released a report criticizing the use of the flavor enhancer. The report claimed that glutamic acid was now responsible for a wide variety of adverse reactions including "asthma, headache, rashes, nausea, irritable bowel syndrome, paralysis, joint pain, anxiety, depression, diarrhea, baggy eyes, Alzheimer's disease, amyotrophic lateral sclerosis (ALS), Huntington's disease, Parkinson's disease, schizophrenia and death." The report backed such accusations primarily with individual case reports.

This report and numerous anecdotal accounts sent in by consumers did not go unnoticed by the FDA. Its recognition of consumer concern regarding MSG was affirmed by Commissioner of Food and Drugs, David A. Kessler, M.D., in remarks made at the 74th annual meeting of the American Dietetic Association held Oct. 30, 1991:

"MSG has been used as a flavor enhancer for centuries. Although it is safe, we recognize that some sensitive individuals have reactions -- generally mild and transitory symptoms -- when they consume large amounts of the additive. These consumers are well-protected by current regulations -- which require that MSG be disclosed in the ingredient label when the processor adds it to the food.

"MSG is also present in food as a component of hydrolyzed proteins that are themselves used as flavor enhancers. Current rules do not require disclosure of MSG as a component of other ingredients. We are changing these rules.

"Although there is no health concern, many consumers have a strong interest in MSG. They have a right to know when it is present in significant levels in food."

While Kessler affirms MSG's safety in this speech, he goes on to announce the plan to implement "contains glutamate" labeling. Most industry sources believe this is not so much a reflection on MSG safety as it is an issue of labeling. In particular, what concerned the agency was the haphazard use of "no MSG" claims as a marketing tool.

Approximately one month thereafter, a feature on CBS's 60 Minutes added fuel to the fire. Following the lead of anti-MSG advocates, the story primarily used information gathered by Schwartz, interviews with Olney and dramatic case histories. Having heard about the report in advance, industry associations were quick to respond and kept hysteria to a minimum. Nevertheless, the report broadened the reach of anti-MSG organizations.

In September 1992, the FDA again asked FASEB to evaluate the current scientific data related to alleged adverse reactions to MSG. In the Federal Register of Jan. 6, 1993, the FDA proposed, among other things, to amend its "common or usual" name regulations to require that the term "contains glutamate" be declared as part of the common or usual name of autolyzed yeast extracts and certain hydrolyzed proteins.

"If you look at the rational for 'contains glutamate,' it is not supportable by scientific means," says Patti, who also is president of the International Hydrolyzed Protein Council. "The way the proposal is written, it's inconsistent with the stated goals and objectives of food labeling, the FDA and Commissioner Kessler. It's the FDA's answer to getting out of a political situation."

Anti-MSG supporters, however, applaud the proposal as necessary to protecting their health.

"On its own, hydrolyzed proteins generally have an MSG content of approximately 12 to 20%," says Schwartz in his 1992 addended update to his book. "However, some flavoring manufacturers add pure monosodium glutamate to the hydrolyzed protein, increasing the MSG content to 40 or 50%."

Down to the wire

FASEB released a preliminary report in February 1993 determining that additional data would be required for its final report. Currently, FASEB is working on the second part of this study, which will evaluate scientific data pertaining to the biological effects of MSG consumption. To solicit additional data and information for use in the final report, FASEB held a meeting on April 7, 1993, "to provide a public forum for submission of scientific data on the safety of MSG."

Presenters opposing the labeling focused primarily on three areas. First, glutamate is ubiquitous in many foods and all proteins contain up to 20% glutamic acid. In fact, a typical meal can contain nearly 2.5 grams of glutamate without any added MSG.

Patti relates the information gathered when he had a product development chef make three types of soup and tested them versus commercial varieties.

"We bought a bunch of cans and we compared minestrone to minestrone," says Patti. "We found more glutamate in home-cooked foods than in processed foods."

Not only does free glutamate occur naturally, labeling of glutamate is made difficult because its levels in finished food are hard to track down since they depend on how the food is processed, how ripe the vegetable is, how aged the beef is, etc.

"In the meat industry, the moment you slaughter the animal the meat is bland," says Nagadowithana. "During aging or curing, there is a certain amount of hydrolysis which releases glutamic acid. Only after this point is the meat put out for sale."

The anti-MSG forces counter such information by stating that naturally occurring glutamate is different than added glutamate. Research has demonstrated, however, that the two are indeed metabolized identically. Casting further doubt on this claim is the fact that at least one anti-MSG testifier at the FASEB meeting emphatically claimed the difference between naturally occurring and added glutamate, yet contradicted himself by saying his own wife's chicken soup affected him.

The second issue is that, in certain enhancers that would be affected by the labeling, the naturally occurring glutamate levels are very low. When used, yeast extracts and many hydrolyzed proteins don't even contribute functional levels of glutamate.

"The whole issue of the 'contains glutamate' labeling is that the levels are so low compared with the total levels of free glutamate," says Nagadowithana. "Because the amount of yeast extract added to a food system is very small, the amount of glutamic acid that goes in is much smaller than what would be natural for the food."

The third major point of the meeting focused on what research exists to objectively substantiate glutamate sensitivity in any but a small segment of the population. Here, the group opposing labeling offered no new information but cited the status of research as summarized earlier in this article. The anti-MSG groups provided personal anecdotal testimonies, restatements of previous research and quotes from the writings of Schwartz. Many such testifiers expressed concern that anecdotal reports are seemingly ignored. Others questioned the validity of double-blind experiments.

People power persists

In spite of such findings and reports, word of mouth still spreads a negative message about MSG. Concerns have particularly grown in the last five to 10 years following the publication of the book, In Bad Taste: the MSG Syndrome, by Dr. George Schwartz (Health Press, Santa Fe, NM, 1988.) The book traces the problems of MSG using the research of Schaumburg and Olney, as well as a number of case histories.

Many consumers – who don't usually apply the restrictions of scientific consensus – found solace in Schwartz's work. Others became quite angry over the seeming lack of government action and decided to speak out.

In 1990, the National Organization Mobilized to Stop Glutamate (NOMSG) released a report criticizing the use of the flavor enhancer. The report claimed that glutamic acid was now responsible for a wide variety of adverse reactions including "asthma, headache, rashes, nausea, irritable bowel syndrome, paralysis, joint pain, anxiety, depression, diarrhea, baggy eyes, Alzheimer's disease, amyotrophic lateral sclerosis (ALS), Huntington's disease, Parkinson's disease, schizophrenia and death." The report backed such accusations primarily with individual case reports.

This report and numerous anecdotal accounts sent in by consumers did not go unnoticed by the FDA. Its recognition of consumer concern regarding MSG was affirmed by Commissioner of Food and Drugs, David A. Kessler, M.D., in remarks made at the 74th annual meeting of the American Dietetic Association held Oct. 30, 1991:

"MSG has been used as a flavor enhancer for centuries. Although it is safe, we recognize that some sensitive individuals have reactions – generally mild and transitory symptoms – when they consume large amounts of the additive. These consumers are well-protected by current regulations – which require that MSG be disclosed in the ingredient label when the processor adds it to the food.

"MSG is also present in food as a component of hydrolyzed proteins that are themselves used as flavor enhancers. Current rules do not require disclosure of MSG as a component of other ingredients. We are changing these rules.

"Although there is no health concern, many consumers have a strong interest in MSG. They have a right to know when it is present in significant levels in food."

While Kessler affirms MSG's safety in this speech, he goes on to announce the plan to implement "contains glutamate" labeling. Most industry sources believe this is not so much a reflection on MSG safety as it is an issue of labeling. In particular, what concerned the agency was the haphazard use of "no MSG" claims as a marketing tool.

Approximately one month thereafter, a feature on CBS's 60 Minutes added fuel to the fire. Following the lead of anti-MSG advocates, the story primarily used information gathered by Schwartz, interviews with Olney and dramatic case histories. Having heard about the report in advance, industry associations were quick to respond and kept hysteria to a minimum. Nevertheless, the report broadened the reach of anti-MSG organizations.

In September 1992, the FDA again asked FASEB to evaluate the current scientific data related to alleged adverse reactions to MSG. In the Federal Register of Jan. 6, 1993, the FDA proposed, among other things, to amend its "common or usual" name regulations to require that the term "contains glutamate" be declared as part of the common or usual name of autolyzed yeast extracts and certain hydrolyzed proteins.

"If you look at the rational for 'contains glutamate,' it is not supportable by scientific means," says Patti, who also is president of the International Hydrolyzed Protein Council. "The way the proposal is written, it's inconsistent with the stated goals and objectives of food labeling, the FDA and Commissioner Kessler. It's the FDA's answer to getting out of a political situation."

Anti-MSG supporters, however, applaud the proposal as necessary to protecting their health.

"On its own, hydrolyzed proteins generally have an MSG content of approximately 12 to 20%," says Schwartz in his 1992 addended update to his book. "However, some flavoring manufacturers add pure monosodium glutamate to the hydrolyzed protein, increasing the MSG content to 40 or 50%."

Down to the wire

FASEB released a preliminary report in February 1993 determining that additional data would be required for its final report. Currently, FASEB is working on the second part of this study, which will evaluate scientific data pertaining to the biological effects of MSG consumption. To solicit additional data and information for use in the final report, FASEB held a meeting on April 7, 1993, "to provide a public forum for submission of scientific data on the safety of MSG."

Presenters opposing the labeling focused primarily on three areas. First, glutamate is ubiquitous in many foods and all proteins contain up to 20% glutamic acid. In fact, a typical meal can contain nearly 2.5 grams of glutamate without any added MSG.

Patti relates the information gathered when he had a product development chef make three types of soup and tested them versus commercial varieties.

"We bought a bunch of cans and we compared minestrone to minestrone," says Patti. "We found more glutamate in home-cooked foods than in processed foods."

Not only does free glutamate occur naturally, labeling of glutamate is made difficult because its levels in finished food are hard to track down since they depend on how the food is processed, how ripe the vegetable is, how aged the beef is, etc.

"In the meat industry, the moment you slaughter the animal the meat is bland," says Nagadowithana. "During aging or curing, there is a certain amount of hydrolysis which releases glutamic acid. Only after this point is the meat put out for sale."

The anti-MSG forces counter such information by stating that naturally occurring glutamate is different than added glutamate. Research has demonstrated, however, that the two are indeed metabolized identically. Casting further doubt on this claim is the fact that at least one anti-MSG testifier at the FASEB meeting emphatically claimed the difference between naturally occurring and added glutamate, yet contradicted himself by saying his own wife's chicken soup affected him.

The second issue is that, in certain enhancers that would be affected by the labeling, the naturally occurring glutamate levels are very low. When used, yeast extracts and many hydrolyzed proteins don't even contribute functional levels of glutamate.

"The whole issue of the 'contains glutamate' labeling is that the levels are so low compared with the total levels of free glutamate," says Nagadowithana. "Because the amount of yeast extract added to a food system is very small, the amount of glutamic acid that goes in is much smaller than what would be natural for the food."

The third major point of the meeting focused on what research exists to objectively substantiate glutamate sensitivity in any but a small segment of the population. Here, the group opposing labeling offered no new information but cited the status of research as summarized earlier in this article. The anti-MSG groups provided personal anecdotal testimonies, restatements of previous research and quotes from the writings of Schwartz. Many such testifiers expressed concern that anecdotal reports are seemingly ignored. Others questioned the validity of double-blind experiments.