BONE-BUILDING ESSENTIALS include foods rich in calcium and vitamin D--such as fortified milk and cheese--or vitamin and mineral supplements. Weight-bearing exercise also keeps bones strong and healthy. Image: GETTY IMAGES (glass of milk); JONELLE WEAVER Getty Images (cheese); FRAN¿OISE SAUZE Photo Researchers, Inc. (calcium pills); JANEART Getty Images (woman walking)
Millions of years ago our ancestors emerged from the sea and evolved into land mammals that confronted a serious problem: how to satisfy their calcium needs, now that absorbing calcium from seawater was no longer an option.
Humans and other mammals evolved an ingenious solution to the calcium challenge, relying on our own skeletons--where 99 percent of bodily calcium resides--as calcium "banks." In a process known as calcium homeostasis, the mineral is deposited into or withdrawn from the skeleton so that blood levels are kept within the narrow range essential for nerve conduction, blood clotting, muscle contraction and other vital physiological functions. Unfortunately, this process is at the root of osteoporosis, because it calls for sacrificing the skeleton if that is what it takes to maintain adequate blood calcium levels.
This article was originally published with the title Restoring Aging Bones.