Author: Tsukamtot Y, Ichise H and Yamaguchi M
Publication: Journal of Health Science, 51,191-196, 2005
Osteoporosis, which is still a major health problem, causes loss of bone mass and increases the risk of bone fractures. About 60% of women older than 60 suffer from osteoporosis. Previous studies show that nutrition has an effect on the risk of hip fractures. In vitro studies have shown that isoflavones and vitamin K2 (found in natto, a fermented soy food) stimulate bone formation by osteoblast and at the same time reduces the bone resorption osteoclasts. The intake of zinc has also a protective effect. Traditionally a sufficient intake of calcium and vitamin D is recommended by doctors and dieticians to maintain healthy bones. More recently, it was discovered that vitamin K2 stimulates the formation of the osteocalcin protein, which helps to incorporate calcium into the bones. Epidemiological studies also show that the level of vitamin K2 is lower in the body of people suffering from osteoporosis compared with that of healthy people. Vitamin K is produced by Bacillus natto bacteria which are responsible for the natto fermentation.
This study investigated the influence of the intake of vitamin K2 rich food on bone markers. The researchers measured the levels of the bone marker gamma-carboxylated osteocalcin, which is used as indication of osteoporosis, in the serum of forty-eight volunteers. They found that the serum levels of vitamin K2 and gamma-carboxylated osteocalcin after the intake of reinforced natto. The intake of normal natto (not reinforced with extra vitamin K2) caused no significant increase of serum gamma-carboxylated osteocalcin levels.
The study concluded that the intake of vitamin K2 could stimulate gamma-carboxylation of osteocalcin, thereby stimulating bone formation.