The older we get, the less calcium we absorb.  While babies can absorb 50 to 80 percent of the calcium they eat, older folks may absorb less than 30 percent.  As we age, our stomach makes less acid.  While that may be good for heartburn, it’s not good for nutrient absorption.  Adequate stomach acid is necessary to help the intestines absorb the many nutrients we need more of as we age, such as calcium, folic acid, vitamin B6, and vitamin B12.  Some calcium supplements, especially calcium carbonate, are poorly digested without the help of stomach acid.  As you can see, there is more to osteoporosis than simply downing more calcium.