It has long been thought that microorganisms, particularly lactic acid bacteria (LAB) could provide benefits for human health. In the early 20th century, Elie MetchniNoff advocated the theory of longevity by yogurt that LAB in yoghurt improve microbiota and contribute to health maintenance and longevity. The term “probiotics” was first used by Lilly and Stillwell in 1965. Thereafter, several definitions of probiotics have been proposed. Among them, the definition proposed by Fuller in 1989 that probiotics are “a live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance” is well known. The health effects of probiotics have been reported in a wide range of research fields. Among others, many studies of the regulation of intestinal function for disorders associated with the gastrointestinal tract and allergic rhinitis have been performed in humans. Several systematic reviews and meta-analyses have verified the efficacy of probiotics in irritable bowel syndrome and have concluded that probiotics have beneficial effects on the improvement of irritable bowel syndrome. In addition, meta- analysis on the treatment of allergic rhinitis has provided evidence of beneficial clinical effects of probiotics. In this review, we have focused on the intestine-regulating function of probiotics and the effect of probiotics on brain function, which is the current topics, as their health effects.

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To evaluate vitamin B12intake for preventing diseases, literature on daily loss of vitamin B12and an associatiobetween dietary vitamin B12 intake and biochemical markers of the vitamin status were investigated and reviewed. Although the current recommended dietary allowance of vitamin B12 for Japanese adults is set at 2.4μg per day, the result of this investigation for the daily intaNe of vitamin B12 by Japanese adults suggests that the daily intake of vitamin B12 (5-6 μg/day) is needed to compensate for its daily loss and to maintain its adequate nutritional status. This value would be suitable to store a sufficient amount of vitamin B12 in body for preventing elderly from its deficiency caused by malabsorption of its food-bound form. Vitamin B12 plays an important role in cellular folate metabolism. Therefore, the recommended daily intake of folate has also been discussed.

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I tried to calculate the saturation amounts of vitamins for humans based on the data concerning the urinary excretion of vitamins. The saturated amounts of vitamins B1, B2, B6, and C were 1.2 mg/1,000 kcal, 2.2 mg/1,000 kcal, 0.054 mg/g protein, and 210 mg/d, respectively. Those of nicotinamide, pantothenic acid, folic acid, and biotin were 28 mg/1,000 kcal, 28 mg/d, 0.77 mg/d, and 0.09 mg/d, respectively. The values of these vitamins were almost 3-fold higher than those of Dietary Reference Intakes of vitamins which are established by the Ministry of Welfare and Labor. In addition, I surveyed a functional biomarker of vitamins. The participants were divided into three groups using the upper (n=10), middle (n=9), and lower tertiles (n=10) based on the urinary excretion amounts of 2-oxo acids. The administration of capsules containing the daily necessary amounts of vitamins led to a decrease in the urinary excretion in participants belonging to the upper tertile. A similar phenomenon was observed in the middle tertile, but not in the lower tertile. Thus, urinary 2-oxo acids might be useful functional biomarkers for vitamin nutritional status.

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