Vitamin A was discovered approximately 200 years ago, and it is accepted as an important nutrient that plays a variety of roles in the human body. Retinoic acid is an active form of vitamin A, which functions as a differentiation-inducing agent (anti-cancer agent) in patients with promyelocytic leukemia. It is also highly likely that retinoic acid may be used to treat other cancers and illnesses. Recently, it was found that other retinoids besides retinoic acid have anti-cancer activities. In this paper, we present findings regarding a new supply of vitamin A and its action in the body, including 1) The action of β-carotene with red palm oil as its source; 2) The immunostimulatory action of retinoic acid in intestines; 3) New technologies related to vitamin A [visualization of retinoic acid; methods for examining decomposition of retinoic acid-binding protein, new methods for determination of retinoic acid by LC/MS/MS] and 4) New materials related to vitamin A [antioxidant and anti-cancer actions of new compounds developed from retinoic acid derivatives (non-genomic actions)]. We plan to examine methods of utilizing complementary food sources of vitamin A, and to apply this to preventive and curative medicine. This research contributes to improving the quality of life of both healthy persons and patients.

Vitamin D plays an important role in the regulation of calcium homeostasis and bone metabolism. Among the vitamin D metabolites, serum 25-hydroxyvitamin D (25-D) concentration is the best indicator of vitamin D status. Vitamin D insufficiency is known to cause secondary hyperparathyroidism, which adversely affects bone metabolism. In addition, vitamin D insufficiency has been associated with other health outcomes including not only osteoporotic fractures but also cardiovascular disease, fall, skeletal muscle function, cancers, respiratory diseases, and all-cause mortality. However, substantial debate about the optimal vitamin D status to prevent those diseases has been continued. Present paper would review the recent knowledge of vitamin D function, meta-analyses of randomized trials of vitamin D supplementation and the requirement of vitamin D.

To elucidate the effects of vitamin E on vitamin K metabolism, we determined the effect of tocopherol intake on vitamin K concentrations in rats fed phylloquinone (PK). Dietary intake of α-tocopherol (αT) for 6 weeks decreased PK concentrations in extrahepatic tissues but not in liver in rats. Oral administration of αT by gavage decreased PK concentrations in some extrahepatic tissues but not in liver. Tocopherol hydroxylase, the rate-limiting enzyme of tocopherol catabolism, also catalyzed PK hydroxylation, the first step of PK catabolism. We determined the effect of sesame lignan, an inhibitor of tocopherol catabolism, on vitamin K concentrations in rats. Dietary intake of sesamin for 7 days increased PK, menaquinone-4, and tocopherol concentrations in rat liver. These data demonstrate that metabolic change of tocopherol influences PK concentrations.

Vitamin K is an essential factor for posttranslational modification (γ-glutamylcarboxylation) of vitamin K-dependent proteins including blood coagulation factors and bone matrix proteins. However, there are many reports regarding novel functions of vitamin K; inhibition of cell proliferation and induction of differentiation in tumor cells, and activation of nuclear receptor SXR/PXR. After ingestion from foods, vitamin K is converted to menaquinone-4, one of vitamin K2, which has geranylgeranyl moiety at 3 position of 2-methylnaphthoquinone, in various organs in human and rodent. UbiA prenyltransferase domain containing 1, UBIAD1, was identified as one of crucial enzyme for this conversion, but entire conversion process has still not elucidated completely. In this review, we described recent knowledge of menaquinone-4 conversion, novel functions of vitamin K, specially menaquinone-4, and discussed physiological meaning of menaquinone-4 conversion in tissues.

Vitamin K is one of the fat soluble vitamin which is discovered as cofactor for blood coagulation. Meanwhile, accumulating evidence from recent research suggests that vitamin K has protective effect against osteoporosis and atherosclerosis. Vitamin K is essential for activation of the calcium-binding proteins called osteocalcin and matrix Gla protein, which contribute to bone and vascular health. The required dairy intake of vitamin K for bone health is greater than dietary reference intakes in Japan. Menaquinone-7, a major homologue which is abundant in natto, has the highest nutritional effect.