Industry defends MSG
Research and reported in the latest issue of the New
Scientist, suggested that diets high in the flavour enhancer
monosodium glutamate could lead to vision loss. The glutamate
industry, quick to respond to the study, has issued a variety of
statements that seek to balance the allegations.
A recent study from Japan, published in Experimental Eye Research and reported in the latest issue of the New Scientist, suggested that diets high in the flavour enhancer monosodium glutamate could lead to vision loss. The glutamate industry, quick to respond to the study, has issued a variety of statements that seek to balance the allegations.
The International Glutamate Information Service in particular has issued a lengthy response, extracts of which we have selected for publication.
In a statement, the IGIS writes: "It is absurd to suggest that eating glutamate can have an adverse effect.
"Glutamate is a safe food ingredient and a natural component of many foods we eat as part of a normal diet. The body treats glutamate in exactly the same way whether it comes from these sources or from seasoning added to food.
"In addition, the body actually produces glutamate."
With reference to the doses of MSG given to the rats during the Japanese study, IGIS made the following response.
"The doses of glutamate fed to the rats were extremely high (neither of the experimental diets supplemented with glutamate could be considered simply 'high' let alone 'moderate'). The amount of the diet represented by added glutamate could not be replicated in a meal for human consumption.
Each day the average person consumes between 10g and 20g of glutamate as part of their normal diet, most of which is consumed as glutamate in the protein in foods. The amount of glutamate used as seasoning is in the range of 0.1 per cent to 0.8 per cent of the food consumed (0.1 to 0.8 g/100g of food).
Lead researcher Hiroshi Ohguro acknowledged in Experimental Biology that "large amounts of MSG were used, 20 per cent of the total diet in the highest group. Lesser amounts should be OK," he said, "but the precise borderline amount is still unknown."
The IGIS responded: "The amount of glutamate fed to the rats represented between 9 per cent and 16.6 per cent of the total diet (either 10g or 20g of monosodium glutamate added to 100g of feed). These amounts could only be considered abuse doses and are completely irrelevant to human nutrition or glutamate consumption.
"The amount of glutamate used to season food is a fraction of the levels cited in this experiment (0.1 per cent to 0.8 per cent of food consumed).
"Monosodium glutamate is a self-limiting ingredient - once an appropriate amount has been added, using more contributes little, if any, additional flavour. Indeed, the addition of too much monosodium glutamate, as seasoning, can result in a decline in palatability of the food to which it is added. At the levels indicated by the experimental diets the food is likely to be inedible."
According to IGIS, Ohguro's hypothesis that the findings might explain why, in eastern Asia, there is a high rate of normal-tension glaucoma, totally ignores "the wealth of scientific data which supports the safety of glutamate. Hundreds of scientific studies have been conducted on glutamate with the focus on its use as a food ingredient.
This extensive body of research, reviewed by scientists and regulatory authorities around the world, together with its long history of use, demonstrates that glutamate is safe."
Finally, suggestions from Peng Tee Khaw, a glaucoma specialist at Moorfields Eye Hospital in London that "if you're a sodium glutamate junky, then you could potentially run into problems with your retina," and that lower dietary intakes could produce the same effects over several decades, were totally refuted by IGIS.
"The allegation that 'lower dietary intakes could produce the same effects over several decades' has no basis in science. This statement ignores what we know about glutamate's role in the body and its metabolism.
The body contains about 1,800 g of glutamate (in a 70 kg adult) of which about 10g is free glutamate. Between 10g and 20g of glutamate is consumed everyday and absorbed for use by the body in normal metabolism.
The body itself produces glutamate during normal metabolism - approximately 48g of glutamate is turned over in the body everyday. In addition, the average person excretes about 16g of glutamate everyday.
Glutamate, from whatever source, consumed as part of a normal diet would be metabolised and would not build up in the manner described," concluded the industry association.
