Dolly Parton sings, “These old bones will tell your story, these old bones will never lie.” But your bones only tell part of your story because every 10 years, you have a completely new skeleton. This is a little known fact that I love relaying to my patients in the University of Alabama at Birmingham Osteoporosis Prevention and Treatment Clinic because it really surprises people.
We think of our bones as being with us our whole lives but our bones are in a constant state of flux. Cells called “osteoclasts” break down old bone and make way for cells called “osteoblasts” to come along and build new bone in its place. The rate of this “bone turnover” ends up replacing much of our adult bone content from the previous 10 years! The size and shape are still the same – but the bone content itself is all new. So if you’re 45, your skeleton is not really made up of any of the same bone you had at 35.
This bone remodeling also paves the way for bone loss later in life because as we get older the osteoclasts speed up and the osteoblasts slow down. In other words, we are losing more bone than we can replace. For women, this is a particular problem as our estrogen levels drop with menopause. Estrogen slows down the osteoclasts (the cells that break down old bone) so when we lose estrogen we lose bone much more quickly.
That loss of estrogen also lowers the percent of calcium we women absorb. This is why women need more calcium as we get older. Our needs jump from 1000 mg a day to 1200 mg once we start menopause. While getting enough calcium alone is unlikely to completely stave off the effects of age and estrogen loss on our bones, it does help slow the loss. But before you start popping calcium supplements, think about what you’re getting from foods in dairy foods like milk, cheese, yogurt, as well as calcium-fortified foods. For example, one cup of milk has 300 mg of calcium, while an ounce of cheese or small carton of yogurt has 150 to 200 mg. Dairy foods have the added benefit of protein and phosphorus, which benefit your bones.
To keep your ever-changing bones healthy throughout a lifetime, enjoy dairy foods or recipes made with dairy!
Beth Kitchin, PhD, RDN is presently an assistant professor in the UAB Department of Nutrition Sciences where she teaches several undergraduate and graduate courses. She is also the director of the UAB Minor in Nutrition Sciences. She has been the patient educator in UAB’s Osteoporosis Prevention and Treatment Clinic since 1997. You can see Dr. Kitchin every Tuesday on Birmingham’s Fox 6 morning program Good Day Alabama. She is also a popular actress on the local Birmingham theatrical scene.