Abstract
Vitamin deficiency causes classical deficiency diseases. Vitamin insufficiency is milder than vitamin deficiency but it increases the risk of non-communicable diseases (NCDs). Considering the importance of NCDs in Japan, vitamin requirement must be determined based on the risk reduction of NCDs. In Dietary Reference Intakes (DRIs) for Japanese 2015, vitamin B12requirement was determined based on the treatment outcome of anemia in patients with pernicious anemia, a vitamin B12deficiency disease, after intra-muscular injection of vitamin B12. However, there are various problems in this determination of vitamin B12requirement in DRIs for Japanese 2015. One of the problems is that the number of subjects is extremely small (N=7).
Therefore, we attempted to propose a novel method to determine vitamin B12requirement based on the risk reduction of diseases. In the determination of vitamin B12requirement by this method, the risk of osteoporotic fracture due to vitamin D insufficiency was taNen into consideration. It was thought that vitamin D requirement determined by DRI in USA/Canada 2011 could be of use as a reference because the vitamin D requirement was determined by taking the risk of osteoporotic fracture due to vitamin D insufficiency into consideration. Vitamin B12or folate insufficiency causes hyperhomocysteinemia which is the risk factor of cardiovascular diseases and osteoporotic fracture. Our recent analysis of cohort studies led to the following findings: plasma homocysteine (Hcy) concentration made a good prediction for the risN of osteoporotic fracture and cardiovascular events. The cut-off value of plasma Hcy concentration to avoid such risks was less than 10 nmol/mL. This cut-off value of plasma Hcy concentration was lower than that cited in DRIs for Japanese 2015 (14 nmol/mL). To avoid this insufficiency, vitamin B12 requirement was much higher than that considered for a long time.
In conclusion, we have proposed a novel method to determine vitamin B12requirement based on the risk reduction of diseases. The application of this method to the decision of DRIs in the future could be awaited.
