What does Estrogen do for bones?
The association of healthy bones and estrogen is a life long story. Simply, estrogen regulates bone turnover. A healthy and controlled rate of bone turnover is needed to replace old bone with new bone. Older bones become weaker. When these processes are in harmony, bones are healthy and strong, regardless of slight variations in density. 
Now, the condition of issue, especially for women, is when estrogen production slows down. The resulting lower estrogen levels are no longer able to control the balance between the build up and the tear down of bone. During the years before this happens, buildng up strong bones certainly helps cover for the now lower estrogen levels. Greater tear down and less build up are often the case. Over time this generates holes in bones which makes bones more susceptible to fracture. Hormone replacement therapy has some value here to continue slowing down bone turnover, but has some other problems.
During this estrogen slow down period, there is still some bone building activity going on that needs to be supported. The 10 nutrient bone building team helps this activity.
Estrogen does not get all the blame here. There is another process that needs to be addressed. (ARORC) This process relates to the lifespan of bone building cells. These cells have a certain programmed lifespan which needs to be conserved. What could shorten this lifespan? It turns out that when bone building cells, called osteoblasts, are called upon to handle extra calcium in the blood stream, they pack this extra calcium into bone mineral reservoir cells. During this activity, some of these bone cells die. Plus others use up some of their given lifespan. While this increases bone density, usually a positive for bone health, the death of some of the osteoblasts in this matter could create shortages or reduce numbers when the actual building of bone tissue and not just reservoir storage occurs.
A Doctor measured the overall lifespan of bone building cells in people with osteoporosis and found that the average age of the osteobalsts was older that in people with healthy bones. Could consuming large amounts of calcium, recommended to prevent osteoporosis, be speeding up the aging of osteoblasts?
CALCIUM BALANCE
The body likes to mainly be in slightly positive calcium balance, that is consuming just a little more than is eliminated during the day. That amount averages between 250-300 mg. Since calcium absorption percent averages about 30%, to get 300 mg, one needs to consume 3 times that amount, or 900 mg. The Government health agencies like to put a margin of extra safety, thus 1000 mg. recommendation. BUT, the absorption of calcium can vary from 10 to 50%. Box Choy is at 50% while milk is at 30%. As larger amounts of calcium are consumed, the body absorbs a lower percentage. Plus, there are other factors that influence this activity, like sodium decreases calcium utiliaztion by speeding elimination.
The recommendation for calcium from the WHO is 500 mg. In Europe, it is 750 mg.
How do natives in South Aftrica have strong bones only consuming about 300 mg of calcium daily? They simply have a lifestyle and diet that protects and maintains calcium balance already in the body, and they absorb a very high percentage in the diet.
Other factors for calcium movment in the body include weight-bearing exercise and the consumption of fruits and vegetables. Not much calcium in most fruits and vegatables, but the other minerals such as potassium act to protect the calcium that is already in bones from performing taken out of bone reservoirs for pH acid balance.