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Clinical nutrition

Reply to readers’ comment to: ‘Effect of monosodium L-glutamate (umami substance) on cognitive function in people with dementia’

We would like to thank Dr. Harper-Hanigan for the feedback on our manuscript entitled ‘Effect of monosodium l-glutamate (umami substance) on cognitive function in people with dementia’ [1] and for openly sharing pertinent thoughts.

A previous study [2] that examined the Touch Panel-type Dementia Assessment Scale (TDAS) reported its relevance to the Alzheimer’s Disease Assessment Scale for patients with Alzheimer’s disease only. However, the TDAS subscale comprises nine examination items measuring memory disturbance, orientation disturbance, visuospatial agnosia, executive function disorder, dyscalculia and other cognitive abilities; therefore, we considered the TDAS adept at evaluating general cognitive functions and accordingly used it for the subjective evaluation of cognitive symptoms. Furthermore, to maintain transparency and vouch for accuracy of our results, we presented not only the total score of the TDAS but also the results for all sub-items. As you astutely pointed out, the small number of subjects precludes stratification by dementia type, and we concur with the notion that recruitment of patients with different dementia types is worth considering in future investigations.

Regarding the ingestion of monosodium l-glutamate (MSG) or NaCl, these additives are added to rice porridge, miso or other soups or mixed in the main dish. The intake of meals containing MSG or NaCl was evaluated by a nursing caregiver. We excluded subjects whose total number of days during which the diet mixed with MSG or NaCl was ingested did not exceed three-quarters of the intervention period. In addition, because this study was conducted at multiple sites and the contents of the diet could not be harmonised, the total intake of the diet was not evaluated. In concordance with your recommendation, changes in urinary sodium levels deduced from 24-h urine sodium ion excretions, as demonstrated previously [3], can provide a comprehensive measure of the objective markers related to MSG and NaCl intake. However, this approach requires strict management of the whole diet.

We hope that readers would take these limitations into account when considering the results presented in our study.

References

  1. 1.

    Kouzuki M, Taniguchi M, Suzuki T, Nagano M, Nakamura S, Katsumata Y, et al. Effect of monosodium L-glutamate (umami substance) on cognitive function in people with dementia. Eur J Clin Nutr. 2019;73:266–75.

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    Inoue M, Jimbo D, Taniguchi M, Urakami K. Touch Panel-type Dementia Assessment Scale: a new computer-based rating scale for Alzheimer’s disease. Psychogeriatrics. 2011;11:28–33.

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    Beauchamp GK, Bertino M, Engelman K. Failure to compensate decreased dietary sodium with increased table salt usage. JAMA. 1987;258:3275–8.

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Correspondence to Minoru Kouzuki.

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Kouzuki, M., Taniguchi, M., Matsumoto, H. et al. Reply to readers’ comment to: ‘Effect of monosodium L-glutamate (umami substance) on cognitive function in people with dementia’. Eur J Clin Nutr 73, 967 (2019). https://doi.org/10.1038/s41430-019-0437-6

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