A part of the bone is always dissolved and absorbed by osteoclast （bone resorption）. And osteoblasts form a new bone （osteoplasty）. When this balance collapses, it leads to the disease called the bone metabolism abnormality symptom, and the most common example is osteoporosis.
In male and female, the bone mass reaches maximum in mid-30 years old and decreases gradually with aging afterward. It is revealed that estrogen greatly participates in maintaining a bone mass. Because in the women in particular, the sudden decrease in bone mass happens for postmenopausal 5-10 years, and there is knowledge such as there being fewer losses of the bone mass than the woman who is irregular in the women who are stable in their menstrual cycle. It is known that the soy isoflavone has weak estrogen-like activity. The effects of isoflavones on bone are confirmed not only in vitro examination but also in animal experiment and a clinical trial. It is thought that these effects act by mechanism same as bone resorption restraint action of estrogen.
Black soybean, a type of soybean with a black seed coat, has been widely used as a nutritionally rich food in Asia. Black soybean has been utilized as a traditional Chinese medicine for preventing of cardiovascular diseases, improving aging liver and kidney functions, and for accelerating diuretic action. Black soybean seed coat contains numerous bioactive compounds including proanthocyanidins and anthocyanins. These compounds have activity as radical scavengers, anti-diabetic and anti-inflammatory agents, and for improving the fluidity of blood. These multiple activities may have some effects on endothelial function.
