Mental disorders such as depression, anxiety and dementia account for the largest proportion of the five major diseases designated by the Japanese Ministry of Health, Labour and Welfare, and the increasing number of patients affected annually is a serious problem. Several peptides produced by the enzymatic digestion of food proteins are known to have physiological effects, and their activities on the central nervous system have recently been reported. In the present study using animal behavioral tests for screening, we identified small peptides effective for modulation of depressive-like behavior, anxiety-like behavior, and cognitive function. Active dipeptide candidates were identified by analyses of structure-activity relationships and biokinetics, and mechanistic analysis revealed their involvement in neurogenesis promotion and monoamine pathway activation. Our findings suggested that food-derived small peptides have strong and orally active neural modulatory effects. Some of the interactions between various molecular species of peptide and the central nervous system were also clarified.

Focusing on the beneficial effects of the “Yakult”-exclusive probiotic strain Lactobacillus casei strain Shirota (LcS) on the gut environment, we have been studying new functions of LcS involving the brain-gut axis. In order to maximize the effects of LcS on the brain-gut axis, we have succeeded in increasing the number and concentration of LcS in fermented milk by improving the raw materials and culture techniques. Double-blind, placebo-controlled trials were conducted to examine the effects of this new fermented milk product containing a high count and high density of LcS on psychological and physiological stress responses in healthy medical students under academic examination stress. This revealed that the increased expression of psychological and physical stress markers observed under stress conditions was significantly suppressed in the LcS group relative to the placebo group. In a different trial, daily consumption of LcS maintained sleep quality during the period of increased stress. Based on these results, we have registered the new LcS product as a “Food with Functional Claims”, allowing its functionality to be shown on the package.

Vitamin Ks are a generic term of several molecules found in natural and processed foods that play an important role in human health for blood coagulation and bone metabolism. Milk contains a higher proportion of menaquinone-4 (vitamin K₂) than phylloquinone (vitamin K₁), which is primarily found in vegetable oils. Infant formula contains an optimized ratio of phylloquinone and menaqunone-4 to support infant growth. According to the Food Labelling Act in Japan, the amounts of vitamins must be listed. However, the current standard method for vitamin K needs large amounts of silica gel and organic solvents and requires significant time to purify and separate major and minor constituent vitamin Ks from impurities. In this process, the quantities of silica gel and organic solvents pose environmental hazards. We have developed an analytical procedure for quantification of phylloquinone and menaquinone-4 using catalytic reduction in liquid chromatography with fluorescence detection. By focusing on silica gel particle size to reduce the quantity of silica and organic solvent required, this method has become an efficient and eco-friendly analytical procedure for vitamin K. In addition, the method reduces the analytical preparation time required for milk, infant powder formula, liquid infant formula and plant oils.

The purpose of this study was to develop a food composition table for estimating the intake of trans fatty acids. We further examined whether the intake of trans-fatty acid estimated by this food composition table was reasonable for middle-aged and elderly men and women with borderline diabetes. We used 23 literature sources to calculate the average content of trans fatty acids per 100 g of 280 foods. For foods not reported in the literature, the trans fatty acid contents were replaced with those for similar foods. Finally, we calculated the average content of trans fatty acids per 100 g of food for 592 food items. We then calculated the average intake of trans fatty acids for 35 men and women with borderline diabetes using a 7-day continuous dietary record. The trans-fatty acids in 4,535 (99.9％) of the total 4,539 foods containing 1 g or more of fat per 100 g of the edible portion were calculated. The average intake of trans fatty acids was 0.66 g (％energy: 0.33％). Although it is necessary to consider the accuracy of this food composition table due to several limitations, our findings suggest that the food composition table for trans fatty acids we have developed may be reasonable for use in a nutritional survey for other groups in the Japanese population.