Minerals, vitamins, and phytochemicals, present in trace amounts in the diet, play important roles in regulating multiple metabolic systems as well as bone metabolism. For clinical screening of phytoestrogen levels in large populations, time-resolved fluoroimmunoassay (TR-FIA) has been developed, and later applied for animal studies as well. Since the intestinal environment affects phytoestrogen metabolism, we investigated how a combination of prebiotics and isoflavone intake would affect isoflavone metabolism in models of osteoporosis. Equol, an isoflavone metabolite, contains enantiomers, and the (S) form is considered to exhibit higher bioavail­ability than the (R) form, associated with a stronger inhibitory effect on bone loss in osteoporotic rodents. However, hesperidin, a citrus bioflavonoid, is thought to suppress bone loss via a cholesterol synthesis pathway different from isoflavone-related mechanisms. Sulforaphane, an anti-inflammatory sulfur-containing compound, has been considered to regulate osteoclast differentiation through suppression of osteoclast fusion molecules in addition to conventional suppression of osteoclast differentiation factors. Finally, with regard to minerals, it has been reported that lipid peroxidation is unlikely to occur in an iron-deficient state. However, in contrast to the conventional theory, we demonstrated that the in vivo oxidation mechanism was caused by iron deficiency. Furthermore, we suggested that metabolism of β-carotene and α-tocopherol was changed during iron deficiency, since it may require an iron-containing enzyme.

“Dietary Reference Intakes for Japanese” [DRIs], published by the Ministry of Health, Labor and Welfare, is the only comprehensive guideline for diet and nutrition available in Japan. This review introduces the main points that it contains, with particular reference to the recent revision, and discusses the relationship between the DRIs and nutritional research, with a view to developing future versions. Although the revisions of the values in the DRIs have been minimal, some of the definitions and their usage have been revised and explained in more detail. Issues related to how dietary intake standards are formulated on the basis of scientific reports are also covered, especially systematic reviews and meta-analyses of previous nutritional studies. The most important message seems to be that data from research on this field in Japan has not been sufficient in either quantity or quality for development of the DRIs, and there is a concern that this may hinder the development of new versions in the near future. It is hoped that researchers working in the field of food and nutrition will tackle this issue and respond positively to this statement. This article does not reflect the official opinion of the Japanese government.

The sense of taste functions as a nutrient sensing system and plays regulatory roles in energy and nutrient intake. The purpose of this study was to determine whether or not taste sensitivity exhibits seasonal variations in young women. The stimulation and recognition thresholds for salty, sour, sweet, umami and bitter tastes were determined during the summer (Jul‐Aug) and winter (Jan‐Feb) seasons in female college students. The results showed that the stimulation thresholds for salty and sweet tastes were significantly higher in the winter than in the summer. The recognition thresholds for salty, sour, sweet and bitter, but not umami, tastes were significantly higher in the winter than in the summer. These findings suggest that taste sensitivities are generally lower in winter than in summer.