Complex processes are often inﬂuenced by a host of diﬀerent factors. That is certainly true for bone building. In addition to calcium, some of the things you can tinker with that inﬂuence bone growth are exercise, the sex hormones estrogen and testosterone, and nutrients such as vitamin D, vitamin K, and ﬂuoride. The amount of protein in your diet also might make a diﬀerence.
• Exercise. A bone bends when some force is applied to it. Apply a large force and the bend turns into a break. Apply a small one and the bend is minuscule but physiologically important, especially if the force is repeated over and over. Cells inside bone sense physical strain or stress and orchestrate a silent symphony of activity that remodels the bone to make it more dense and stronger. Among children and young adults, vigorous physical activity sketches the blueprint for the growing skeleton. The more activity and healthy stress on bones, the more bone is built and the larger the bone reservoir upon which to draw during adulthood and old age. During adulthood, exercise helps maintain the balance between bone-building and bone- dissolving processes. During old age, exercise limits bone loss.
Keep in mind that activity doesn’t build or strengthen all bones, just those that are stressed, so you need a variety of exercises or activities to keep all your bones healthy.
While the impact of exercise on bone health is widely accepted, experts haven’t yet deﬁned the best way to maintain strong bones. Some combination of weight- bearing exercises (like brisk walking) and muscle- strengthening exercises will probably turn out to be the ideal combination. Not only would this combination continually stimulate bone growth, but it would also strengthen muscles and improve balance and so help prevent bone-breaking falls.
• Hormones. Two potent members of this class of compounds are estrogen and testosterone. Estrogen is sometimes called the female hormone, and testosterone the male hormone, even though women and men make both. Numerous studies have shown that these two hormones are important for building new bone early in life and for keeping it strong over the next seventy years or so. That’s a problem because production of sex hormones plummets after menopause in women and falls oﬀ more gradually in men.
Hormone replacement therapy, usually with estrogen plus a progestin, was once the ﬁrst-line treatment for preventing osteoporosis in older women. It is an eﬀective way to control the hot ﬂashes that often accompany menopause. It was also thought to help prevent heart disease. Widespread use of hormone replacement therapy ended when results from the federally funded Women’s Health Initiative showed a large increase in breast cancer and a small but signiﬁcant increase in the risk of heart disease and stroke among women who used estrogen with a progestin. Alternatives to estrogen include drugs called bisphosphonates, such as alendronate (Fosamax), etidronate (Didronel), and ibandronate (Boniva); selective estrogen receptor modulators such as raloxifene (Evista); and calcitonin.
learn more: THE DARK SIDE OF CALCIUM AND DAIRY PRODUCTS
The slowdown in sex hormone production in men isn’t as abrupt or as predictable as it is in women. If there are warning signs of osteoporosis, a testosterone check is a good idea for men over age sixty-ﬁve. If levels are low, then daily testosterone gel or patches or biweekly shots of testosterone might be considered.
For women or men, the decision to begin hormone therapy isn’t something to take lightly. It is a complicated issue with rapidly changing options. Weighing the beneﬁts and risks and sorting through these options is best done with a trusted health care provider.
• Vitamin D. This fat-soluble vitamin’s best-known function is helping the digestive system eﬃciently absorb calcium and phosphorus. It helps build and maintain healthy bones in other ways, too (see chapter 10). Several studies have shown that vitamin D deﬁciencies are more common among older people with broken bones than those without them. In the Nurses’ Health Study, older women who got at least 500 International Units (IU) of vitamin D a day were one-third less likely to have broken a hip than women who got under 200 IU a day. Results from randomized trials of vitamin D and fractures have been mixed, but all that used 800 IU per day showed a beneﬁt, while those using lower daily doses did not.The current oﬃcial target for daily vitamin D intake is 200 IU (5 mcg) between the ages of nineteen and ﬁfty; 400 IU (10 mcg) between the ages of ﬁfty-one and seventy; and 600 IU (15 mcg) after age seventy. Yet many lines of evidence point to a higher level—at least 800 IU per day—to get the full beneﬁts of vitamin D.
Few foods naturally contain vitamin D, so you need to get most of yours from either sunlight or supplements. A tablespoon of cod-liver oil delivers more than 1,200 IU. Standard multivitamins carry 400 IU of vitamin D. Don’t take two of these to get extra vitamin D, since a double dose of preformed vitamin A (retinol) might counteract vitamin D’s eﬀects. Some calcium supplements come with added vitamin D, which is a good idea since there is actually better evidence for beneﬁts from vitamin D supplements than for calcium. In addition, the two substances may have a synergistic eﬀect.
learn more: WHY YOU NEED CALCIUM
Can extra vitamin D help prevent osteoporosis-related fractures? Although the evidence isn’t totally consistent, extra vitamin D may be an eﬀective way to prevent bone loss. I certainly agree with an editorial in the New England Journal of Medicine that succinctly concluded, “A widespread increase in vitamin D intake is likely to have a greater eﬀect on osteoporosis and fractures than many other interventions.” For most people, the easiest way to do this is to take supplements that contain vitamin D.
• Vitamin K. Until recently, vitamin K was thought to be necessary mostly for the formation of proteins that regulate blood clotting. It turns out, though, that this fat- soluble vitamin also plays one or more roles in the regulation of calcium and the formation and stabilization of bone. So too little vitamin K may help set the stage for osteoporosis. In the Nurses’ Health Study, women who got more than 109 mcg of vitamin K a day were 30 percent less likely to break a hip than women who got less than that amount. The current recommended daily intake for vitamin K is 90 mcg for women and 120 mcg for men. Vitamin K is found mainly in green vegetables such as dark green lettuce, broccoli, spinach, Brussels sprouts, and kale. Eating one or more servings of these foods a day should give you enough vitamin K. If you take warfarin (Coumadin) or other medications to prevent blood clots, talk with your doctor ﬁrst before boosting your daily intake of vitamin K.
• Fluoride. The same substance that is added to drinking water and toothpaste to ﬁght cavities can also ﬁght osteoporosis. Fluoride therapy is already used in many countries, and the Food and Drug Administration is considering its use in the United States. While low-dose ﬂuoride pills aren’t being eyed as a way to prevent osteoporosis and late-in-life fractures, a ﬂuoride-calcium combination could be a safe, eﬀective way to help treat existing osteoporosis. Fluoride supplements aren’t something to try on your own, though. Early enthusiasm for high-dose ﬂuoride supplements evaporated when later studies showed that the dense bones they helped build were sometimes more brittle and more likely to break. While the amounts of ﬂuoride added to drinking water are perfectly safe, stay away from ﬂuoride supplements unless they are prescribed by your physician.
• Protein. As your body digests protein, it releases acids into the bloodstream. Calcium, drawn mostly from the skeleton, helps neutralize these acids. A number of studies have shown that the more protein consumed, the more calcium excreted in the urine. When it comes to leaching calcium from bone, animal protein is somewhat more powerful than vegetable protein. The connection between protein and calcium loss may explain part of the high rate of broken bones in meat-eating countries such as the United States and those in northern Europe, though the link between protein and bone health is far from settled.