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::Monosodium
Glutamate::
August 31, 1995
Monosodium glutamate (MSG) is used as a flavor enhancer
in a variety of foods prepared at home, in restaurants,
and by food processors. Its use has become controversial
in the past 30 years because of reports of adverse
reactions in people who've eaten foods that contain
MSG. Research on the role of glutamate--a group
of chemicals that includes MSG--in the nervous system
also has raised questions about the chemical's safety. |
The brain. Consumption of glutamate in food, however,
does not cause this effect. While people normally
consume dietary glutamate in large amounts and the
body can make and metabolize glutamate efficiently,
the results of animal studies conducted in the 1980s
raised a significant question: Can MSG and possibly
some other glutamates harm the nervous system? A
1995 report from the Federation of American Societies
for Experimental Biology (FASEB), an independent
body of scientists, helps put these safety concerns
into perspective and reaffirms the Food and Drug
Administration's belief that MSG and related substances
are safe food ingredients for most people when eaten
at customary levels.
The FASEB report identifies two groups of people
who may develop a condition the report refers to
as "MSG symptom complex." One group is
those who may be intolerant to MSG when eaten in
a large quantity. The second is a group of people
with severe, poorly controlled asthma. These people,
in addition to being prone to MSG symptom complex,
may suffer temporary worsening of asthmatic symptoms
after consuming MSG. The MSG dosage that produced
reactions in these people ranged from 0.5 grams
to 2.5 grams.
Although FDA has not fully analyzed the FASEB report,
the agency believes that the report provides the
basis to require glutamate labeling. FDA will propose
that foods containing significant amounts of free
glutamate (not bound in protein along with other
amino acids) declare glutamate on the label. This
would allow consumers to distinguish between foods
with insignificant free glutamate levels and those
that might contribute to a reaction. |
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::What Is MSG?::
MSG is the sodium salt of the amino acid glutamic
acid and a form of glutamate. It is sold as a fine
white crystal substance, similar in appearance to
salt or sugar. It does not have a distinct taste
of its own, and how it adds flavor to other foods
is not fully understood. Many scientists believe
that MSG stimulates glutamate receptors in the tongue
to augment meat-like flavors.
Asians originally used a seaweed broth to obtain
the flavor- enhancing effects of MSG, but today
MSG is made by a fermenting process using starch,
sugar beets, sugar cane, or molasses.
Glutamate itself is in many living things: It is
found naturally in our bodies and in protein-containing
foods, such as cheese, milk, meat, peas, and mushrooms.
Some glutamate is in foods in a "free"
form. It is only in this free form that glutamate
can enhance a food's flavor. Part of the flavor-enhancing
effect of tomatoes, certain cheeses, and fermented
or hydrolyzed protein products (such as soy sauce)
is due to the presence of free glutamate.
Hydrolyzed proteins, or protein hydrolysates, are
acid- treated or enzymatically treated proteins
from certain foods. They contain salts of free amino
acids, such as glutamate, at levels of 5 to 20 percent.
Hydrolyzed proteins are used in the same manner
as MSG in many foods, such as canned vegetables,
soups, and processed meats.
::Scientific Review::
In 1959, FDA classified MSG as a "generally
recognized as safe," or GRAS, substance, along
with many other common food ingredients, such as
salt, vinegar, and baking powder. This action stemmed
from the 1958 Food Additives Amendment to the Federal
Food, Drug, and Cosmetic Act, which required premarket
approval for new food additives and led FDA to promulgate
regulations listing substances, such as MSG, which
have a history of safe use or are otherwise GRAS.
Since 1970, FDA has sponsored extensive reviews
on the safety of MSG, other glutamates and hydrolyzed
proteins, as part of an ongoing review of safety
data on GRAS substances used in processed foods.
One such review was by the FASEB Select Committee
on GRAS Substances. In 1980, the committee concluded
that MSG was safe at current levels of use but recommended
additional evaluation to determine MSG's safety
at significantly higher levels of consumption. Additional
reports attempted to look at this.
In 1986, FDA's Advisory Committee on Hypersensitivity
to Food Constituents concluded that MSG poses no
threat to the general public but that reactions
of brief duration might occur in some people.
Other reports gave similar findings. A 1991 report
by the European Communities' (EC) Scientific Committee
for Foods reaffirmed MSG's safety and classified
its "acceptable daily intake" as "not
specified," the most favorable designation
for a food ingredient. In addition, the EC Committee
said, "Infants, including prematures, have
been shown to metabolize glutamate as efficiently
as adults and therefore do not display any special
susceptibility to elevated oral intakes of glutamate."
A 1992 report from the Council on Scientific Affairs
of the American Medical Association stated that
glutamate in any form has not been shown to be a
"significant health hazard."
Also, the 1987 Joint Expert Committee on Food Additives
of the United Nations Food and Agriculture Organization
and the World Health Organization have placed MSG
in the safest category of food ingredients.
Scientific knowledge about how the body metabolizes
glutamate developed rapidly during the 1980s. Studies
showed that glutamate in the body plays an important
role in normal functioning of the nervous system.
Questions then arose on the role glutamate in food
plays in these functions and whether or not glutamate
in food contributes to certain neurological diseases.
::Anecdotal Evidence::
Many of these safety assessments were prompted by
unconfirmed reports of MSG-related adverse reactions.
Between 1980 and 1994, the Adverse Reaction Monitoring
System in FDA's Center for Food Safety and Applied
Nutrition received 622 reports of complaints about
MSG. Headache was the most frequently reported symptom.
No severe reactions were documented, but some reports
indicated that people with asthma got worse after
they consumed MSG. In some of those cases, the asthma
didn't get worse until many hours later.
Also, several books and a TV news show have reported
widespread and sometimes life-threatening adverse
reactions to MSG, claiming that even small amounts
of manufactured glutamates may cause adverse reactions.
A problem with these unconfirmed reports is that
it is difficult to link the reactions specifically
to MSG. Most are cases in which people have had
reactions after, but not necessarily because of,
eating certain foods containing MSG.
While such reports are helpful in raising issues
of concern, they do not provide the kind of information
necessary to describe who is most likely to be affected,
under what conditions they'll be affected, and with
what amounts of MSG. They are not controlled studies
done in a scientifically credible manner.
::1995 FASEB Report::
Prompted by continuing public interest and a flurry
of glutamate-related studies in the late 1980s,
FDA contracted with FASEB in 1992 to review the
available scientific data. The agency asked FASEB
to address 18 questions dealing with:
the possible role of MSG in eliciting MSG symptom
complex
the possible role of dietary glutamates in forming
brain lesions and damaging nerve cells in humans
underlying conditions that may predispose a person
to adverse effects from MSG
the amount consumed and other factors that may affect
a person's response to MSG
the quality of scientific data and previous safety
reviews.
FASEB held a two-day meeting and convened an expert
panel that thoroughly reviewed all the available
scientific literature on this issue.
FASEB completed the final report, over 350 pages
long, and delivered it to FDA on July 31, 1995.
While not a new study, the report offers a new safety
assessment based on the most comprehensive existing
evaluation to date of glutamate safety. Among the
report's key findings:
An unknown percentage of the population may react
to MSG and develop MSG symptom complex, a condition
characterized by one or more of the following symptoms:
burning sensation in the back of the neck, forearms
and chest numbness in the back of the neck, radiating
to the arms and back tingling, warmth and weakness
in the face, temples, upper back, neck and arms
facial pressure or tightness ?h chest pain headache
nausea rapid heartbeat bronchospasm (difficulty
breathing) in MSG-intolerant people with asthma
drowsiness weakness.
In otherwise healthy MSG-intolerant people, the
MSG symptom complex tends to occur within one hour
after eating 3 grams or more of MSG on an empty
stomach or without other food. A typical serving
of glutamate-treated food contains less than 0.5
grams of MSG. A reaction is most likely if the MSG
is eaten in a large quantity or in a liquid, such
as a clear soup. Severe, poorly controlled asthma
may be a predisposing medical condition for MSG
symptom complex. No evidence exists to suggest that
dietary MSG or glutamate contributes to Alzheimer's
disease, Huntington's chorea, amyotrophic lateral
sclerosis, AIDS dementia complex, or any other long-term
or chronic diseases. No evidence exists to suggest
that dietary MSG causes brain lesions or damages
nerve cells in humans. The level of vitamin B6 in
a person's body plays a role in glutamate metabolism,
and the possible impact of marginal B6 intake should
be considered in future research. There is no scientific
evidence that the levels of glutamate in hydrolyzed
proteins causes adverse effects or that other manufactured
glutamate has effects different from glutamate normally
found in foods.
::Ingredient Listing::
Under current FDA regulations, when MSG is added
to a food, it must be identified as "monosodium
glutamate" in the label's ingredient list.
Each ingredient used to make a food must be declared
by its name in this list.
While technically MSG is only one of several forms
of free glutamate used in foods, consumers frequently
use the term MSG to mean all free glutamate. For
this reason, FDA considers foods whose labels say
"No MSG" or "No Added MSG" to
be misleading if the food contains ingredients that
are sources of free glutamates, such as hydrolyzed
protein.
In 1993, FDA proposed adding the phrase "(contains
glutamate)" to the common or usual names of
certain protein hydrolysates that contain substantial
amounts of glutamate. For example, if the proposal
were adopted, hydrolyzed soy protein would have
to be declared on food labels as "hydrolyzed
soy protein (contains glutamate)." However,
if FDA issues a new proposal, it would probably
supersede this 1993 one.
In 1994, FDA received a citizen's petition requesting
changes in labeling requirements for foods that
contain MSG or related substances. The petition
asks for mandatory listing of MSG as an ingredient
on labels of manufactured and processed foods that
contain manufactured free glutamic acid. It further
asks that the amount of free glutamic acid or MSG
in such products be stated on the label, along with
a warning that MSG may be harmful to certain groups
of people. FDA has not yet taken action on the petition.
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