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Ajinomoto Group is one of the leading global
producers of the flavor enhancer monosodium
glutamate (MSG). Since early 20th century,
Ajinomoto has gathered a substantial amount of
data related to MSG safety and use. Based on that
database, we are commenting here-below on the
recent article by Abbasi et al., entitled “Effect of
Vitamin C on monosodium glutamate (Ajinomoto)
induced changes in the ovary of rats” (JIIMC 11(2),
2016, 66-70).
The article described a rat study with MSG and
vitamin C. The authors extensively speculated that
MSG ingestion may cause harmful effects on human
female fertility and ovarian functions. We argue that
the study by Abbasi et al. was burdened by
methodological problems and a lack of
reproducibility. In addition, we conclude that the
authors neglected glutamate metabolism in
mammalian bodies in interpreting the results.
1) The doses of MSG or the mode of MSG
treatment were not described, thus one cannot
conclude if there was any relevance to human
nutrition. If MSG was mixed into the
experimental diet, the authors needed to explain
how that was achieved since conventional rat
diets are granulated. If MSG was applied in
drinking water, the authors needed to describe
how taste was masked.
2) No data on diet intake, water intake or body
weight were provided, but the authors
mentioned that the control group was
characterized by a lower terminal mean body
weight when compared to body weight of
MSG–treated rats. Therefore, the observed
ovarian differences could have been attributed
to the changes in body weight and not to the
treatments per se. In other words, in the absence
of body weight information, it is impossible to
toxicologically interpret the observed changes.
3) It is not clear where the tested MSG was
obtained from, who was the producer and
whether it contained impurities or other
substances which may have affected the
observed results.
4) The authors indicated that "AJINOMOTO" was a
common name of all MSG used in Pakistan.
Indeed, "AJINOMOTO" is a trademark registered
by Ajinomoto Co., Inc. in more than 170
countries, including countries in Central and
South Asia. However, while the “AJINOMOTO” is
one of the most popular seasoning brands worldwide, it is not the only MSG brand on the market.
Mentioning “AJINOMOTO” brand name in a title
of a scientific article without describing the
source of the tested MSG, or its purity, was
disparaging and academically unjustified.
5) As the authors mentioned, a molecule of MSG
contains glutamate and sodium. However,
sodium intake from MSG was not controlled for
even though the authors attributed all observed
changes to glutamate alone. One cannot
preclude that at least some effects were
attributable to sodium. In that respect, we note
that there was no information on how control
rats were treated or what control diet was
composed of. Adult rats ingest standard diet at
approximately 12% of their body weight, thus we
suppose the studied female rats ingested daily
approximately 30 – 40 g of a chaw diet. If that
diet was based on milk casein, as is usually the
case, it contained 10% glutamate, so the rats
were eating 3 – 4 g of glutamate from the diet
alone without MSG added (i.e., 1). No attention
was given to that “diet-contained” glutamate
source.
6) Authors extensively speculated on MSG use in
humans. Adult humans ingest about > 10 g
glutamate per day from a normal diet. This
volume includes 0.5 – 1.0 g per day of glutamate
added to food as a flavor enhancer, whether in a
form of MSG or included in other condiments
rich in glutamate (bouillon cubes, soy sauces,
mushrooms etc.). In simple words, MSG is only a
small portion of ingested glutamate. Considering
that all food free glutamates are metabolized
identically, it is disproportionate to speculate
solely on MSG – especially if the speculation is
based on a rodent study only.
7) Importantly, histopathological evaluation of the
tissues was not described. Specifically, was the
evaluation done visually only; and were the
persons conducting the observations blinded?
LETTER TO THE EDITOR
Food-added Monosodium Glutamate does not induce Changes
in the Ovaries
8) Finally, the authors selectively used references
and omitted scientific papers on the lack of
dietary MSG effect on reproductive functions (2-
4). Instead, the authors used pharmacological
studies with MSG or non-scientific articles
published online (See Ref. 17 in the original
article). At this point, it is appropriate to mention
that less than 5% of orally ingested glutamate
from food (including MSG) is absorbed from the
gut into the systemic circulation. The rest is used
as an oxidative substrate by the intestinal
mucosa (5-8). Other food components, which
are inevitably ingested along with food-added
glutamate, further suppress circulating
glutamate levels (9-10) and therefore increasing
blood glutamate levels by food-added MSG is
extremely difficult. In the absence of a high
circulating glutamate, any changes in ovarian
physiology are impossible to attribute to foodderived glutamates, such as MSG
Miro Smriga, Kosuke Tomori, Tatsuo Igarashi. (2016) Food-added Monosodium Glutamate does not induce Changes in the Ovaries, , Volume-11, Issue-3.
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