For proper bone health, it's important to consume adequate calcium. During childhood we are able to absorb up to 75% of the calcium we consume, but as growth slows, so does the calcium absorption rate.
 
Teens absorb 20%- 40% of ingested calcium and adults, on average, absorb around 15%. Also, according to UC Berkeley's New Wellness Encyclopedia, American women consume only about half as much calcium as recommended.