MSG and Retinal Degeneration

In 1957, Lucas and Newhouse(1) first noticed that severe retinal lesions could be produced in suckling mice (and to some extent in adult mice) by a single injection of glutamic acid (glutamate).

Studies confirming their findings using neonatal rodents(2-5) and adult rabbits(6) followed shortly thereafter, with others being reported from time to time (7-12). These studies concerned themselves not only with the confirmation of gltamate induced retinal lesions, but with the formulation and testing of hypotheses to explain the phenomenon.

In 2002, Ohguro et al (13) found that rats fed 10 grams of sodium glutamate (97.5%  sodium glutamate and 2.5% sodium ribonucleotide) added to a 100 gram daily diet for as little as 3 months had a significant increase in amount of glutamic acid in vitreous, had damage to the retina, and had deficits in retinal function, leading to blindness in some cases  .

Ohguro et al.(13) also documented the suspicion of many MSG-sensitive people that there is a cumulative effect to the damage caused by daily ingestion of MSG.

Other reports of toxic effects of monosodium glutamate have come from studies at the University of Pecs, Hungary, where the neuroprotective effects of PACAP in the retina are being studied(14,15).


REFERENCES

1. Lucas, D.R. and Newhouse, J. P. The toxic effect of sodium-L-glutamate on the inner layers of the retina. AMA Arch Ophthalmol 58: 193-201, 1957

2. Potts, A.M., Modrell, R.W., and Kingsbury, C. Permanent fractionation of the electroretinogram by sodium glutamate. Am J Ophthalmol 50: 900-907, 1960.

3. Freedman, J.K., and Potts, A.M. Repression of glutaminase I in the rat retina by administration of sodium L-glutamate. Invest Ophthalmol 1: 118-121, 1962.

4. Freedman, J.K., and Potts, A.M. Repression of glutaminase I in rat retina by administration of sodium L-glutamate. Invest Ophthal 2: 252, 1963.

5. Potts, A.M. Selective action of chemical agents on individual retinal layers. In: Biochemistry of the retina. Graymore, C.N., Ed. New York: Academic Press, 1965. pp 155-161.

6. Hamatsu, T. Experimental studies on the effect of sodium iodate and sodium L-glutamate on ERG and histological structure of retina in adult rabbits. Acta Soc Ophthalmol Jpn 68: 1621-1636, 1964. (Abstract

7. Hansson, H.A. Ultrastructure studies on long-term effects of MSG on rat retina. Virchows Arch [Zellpathol] 6: 1, 1970.

8. Cohen, A.I. An electron microscopic study of the modification by monosodium glutamate of the retinas of normal and "rodless" mice. Am J Anat 120: 319-356, 1967.

9. Olney, J.W. Glutamate-induced retinal degeneration in neonatal mice. Electron-microscopy of the acutely evolving lesion. J Neuropathol Exp Neurol 28: 455-474, 1969.

10. Olney, J.W. Glutamate-induced retinal degeneration in neonatal mice. Electron-microscopy of the acutely evolving lesion. J Neuropathol Exp Neurol 28: 455-474, 1969.

11. Hansson, H.A. Scanning electron microscopic studies on the long term effects of sodium glutamate on the rat retina. Virchows Arch ABT B (Zellpathol) 4: 357-367, 1970.

12. Arees, E., Sandrew, B., and Mayer, J. MSG-induced optic pathway lesions in infant mice following subcutaneous injection. Fed Proc 30: 521, 1971.

13. Ohguro, H., Katsushima, H., Maruyama, I., Maeda, T., Yanagihashi, S. Metoki, T., Nakazawa, M. A high dietary intake of sodium glutamate as flavoring (Ajinomoto) causes gross changes in retinal morphology and function. Experimental Eye Research 75:(3),2002.

14. Babai N, Atlasz T, Tamas A, et al. Search for the optimal monosodium glutaamte treatement schedule to study the neuroprotective effects of PACAP in the retina. Ann N Y Acad Sci. 2006;1070(July):149-155.

15. Szabadfi K, Atlasz T, Horvath G, et al. Early postnatal enriched environment decreases retinal degeneration induced by monosodium glutamate treatment in rats. Brain Res. 2009;1259(March):107-12.