Calcium to Prevent Osteoporosis - Take More!

The totality of the evidence indicates that high calcium intake is important both for prevention and management of osteoporosis, and recent negative trials do not refute the much larger body of positive studies. The challenge is not to haggle over exactly how much is enough but, as the Surgeon General's report on osteoporosis put it, to recognize that current intake is far below optimal values. It is imperative to take action to augment calcium intake, both in the general population and particularly in persons being treated for osteoporosis. For many patients, calcium supplements are the most appropriate choice to ensure adequate intake. A number of different calcium compounds are used in supplements; the 2 main forms are calcium carbonate and calcium citrate. Although absorption of calcium citrate is similar to calcium carbonate, a calcium carbonate supplement contains 40% calcium vs the 21% found in calcium citrate.[52] Because formulations may contain different amounts of calcium, the number of tablets needed to obtain a recommended dose may vary. Figure 6 depicts the amount of calcium found in common compounds. Patients often erroneously believe that they are obtaining sufficient calcium through their diet. However, it is known that the median calcium intake in postmenopausal women in North America is substantially below existing recommendations.[11] Because milk and milk products provide the majority of dietary calcium in the United States, if a person is lactose-intolerant, a vegan (consuming no animal products), or avoids dairy products for other reasons, it may be especially challenging to obtain adequate amounts of calcium solely through diet.[50] In addition to being aware of the amount of dietary calcium they are ingesting, it is important that patients understand that absorption from foods can be affected by a number of factors, many of which have already been well described. These include age, vitamin D, pregnancy, and plant substances in the diet. Oxalates (found in chocolate and spinach) and phytate (found in whole grains) are among dietary substances that impair absorption. Therefore, 8 cups of spinach are needed to obtain the same amount of calcium obtained from an 8-ounce serving of milk or 1 cup of yogurt, which contain calcium in an easily absorbable form.[51] Vitamin D. Although vitamin D status has been discussed as a potential confounder of results in calcium studies, the importance of vitamin D in its own right must also be emphasized. It has long been recognized that vitamin D is important for calcium absorption, and recent studies have demonstrated that absorption efficiency increases with improving vitamin D status up to serum 25(OH)D levels of about 80 nmol/L (32 ng/mL).[43,44] Postmenopausal women, as reported in many studies, tend to have average serum 25(OH)D values ranging from 50 to 55 nmol/L (20 to 22 ng/mL)[43,45] and are therefore absorbing the calcium they ingest with reduced efficiency. Protein. As with vitamin D, protein plays an important role in its own right. Although North Americans are considered to consume generous amounts of protein it is also true that many fragile elderly individuals have low protein intake. If these same individuals are our osteoporosis patients, then they will probably not respond well to pharmacotherapy until their nutritional status is repaired. If deficient in calcium, vitamin D, and protein, many will be unresponsive to monotherapy, whether nutritional or pharmacologic. This is seen most obviously in patients with hip fracture, whose outcomes have been shown to improve dramatically with protein supplementation.[46] Exercise. Bones are designed to bear loads and to resist mechanical forces. Maintenance of adequate bone mass requires continued mechanical loading. Nutrition alone may slow the progress of disuse bone loss, but it will not block its full, ultimate expression. Optimal exercise regimens are uncertain, but impact loading appears to be more osteotrophic than, for example, weight lifting or swimming. In general, patients with osteoporosis need to maintain as vigorous an exercise program as is compatible with their bone fragility status. Good online sources of information for patients about calcium and or bone health include the National Institutes of Health, Office of Dietary Supplements;[51] American Osteoporosis Foundation;[54] and the National Institute of Arthritis and Musculoskeletal and Skin Diseases.[53]