The Doctor Is In
By TeddWeisman, MD
Bone Metabolism 101 and Osteoporosis: What You Should Know
P arents often ask me whether they should feed their child more milk to heal fractures, especially when their child has had more than one fracture in the past few years. In my role as an orthopedic surgeon, I address their question by first asking: “ Is your young child active? Is your child involved in sports such as football, soccer, gymnastics, or other activities such as rock climbing, skateboarding, or snowboarding ?” Invariably, the answer to that question is “Yes.” Then I explain that unless their child has a rare “brittle” bone disease, such as osteogenesis imperfecta, they should expect this active child to have a higher chance of injury than a more sedentary child. Childhood lacerations, bruises and fractures are associated with an active lifestyle, which ironically, is often a sign of good health. What some of these active children need to do is practice more caution in their activities, not refrain from participating in them. My next orthopedic response to the question above is that there are no differences in bone health between milk drinkers and non- milk drinkers. In summary, drinking milk does not : 1) make bones stronger 2) positively affect bone growth 3) hasten bone healing 4) prevent bone fractures In fact, the “got milk?” advertisements were carefully worded to avoid making a direct claim that milk can build strong bones. That is because the science does not prove that statement. The “got milk?” advertisements obliquely touted milk consumption in order to get “strong bones.” The science does not show that milk drinkers have stronger bones than non-milk drinkers, nor is milk consumption correlated with hastening the healing process of fractured bones. In fact, there is clear epidemiologic information which shows the opposite correlation: hip fracture rates are highest among cultures that consume the most cow’s milk. “ If we don’t drink milk, what happens to our bones ?” A study was done to compare the bone density of vegan Buddhist nuns (who are prohibited from consuming dairy products) to a group of non-vegan women. Both groups were controlled for age, height, body habitus and activity routines. In fact, the non-vegan women consumed approximately twice the amount of calcium than the vegan nuns, but the study found no difference in the bone mineral density between these two groups of women. Bone Metabolism 101 is the title of this article, because you are about to get a brief education in orthopedic basic science. This information will help you understand bone growth, bone healing,
and osteoporosis. Armed with this data, you will be better informed during a conversation with your physician about a plan of treatment for your particular bone health needs. There are three things to know: 1. Bone continually undergoes changes . These changes occur during both childhood and adulthood. In childhood, it is called bone growth and bone remodeling . In adulthood, it is known as bone remodeling . Bone remodels to accommodate the daily physical stresses placed on it by activities done against the force of gravity. Bone remodeling is also how bones heal. Bones can become stronger in active individuals, and weaker in sedentary individuals. Here are examples of how bone undergoes changes: • Children grow because their bones lengthen and widen. • Broken (= fractured ) bones mend and heal. • Exercise is a potent way of strengthening bones to prevent and treat osteoporosis, while lack of activity can lead to a phenomenon called Disuse Osteoporosis. (Disuse Osteoporosis will be discussed soon.) 2. Bone is made up of two types of cells: osteoblasts and osteoclasts . These two cells perform opposite functions. The osteoblast cells make bone, and the osteoclast cells remove bone. The “bone as a bank” is a metaphor I often use. The osteoblasts deposit money to the bone bank, and osteoclasts withdraw money from the bone bank. 3. Bone is a storehouse of calcium and other minerals . There are hormones and enzymes that direct the osteoblast cells to make bone , and there are hormones and enzymes that direct the osteoclast cells to remove bone , calcium and minerals from bone . (The human body, in its great wisdom, sometimes needs to remove calcium and minerals from bone when they are needed elsewhere in the body). In general, the level of bone mass remains constant, because the bone-producing effects of osteoblasts equals bone-removing effects of osteoclasts. However, when osteoclast activity outpaces osteoblast activity, bone mineral density decreases. This is what causes osteoporosis. Osteoporosis is defined by the World Health Organization (WHO) as low bone mass (or low bone density). Low bone density results in decreased bone strength. Therefore, people who are diagnosed with osteoporosis are at an increased risk of having a fracture due to low bone density and strength. It is a known fact that women are diagnosed with osteoporosis more frequently than men. The primary reason is that the average
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