Phosphorus Important for Bone Health in Elderly
Although most Americans consume adequate or even excessive amounts of phosphorus in their diets, elderly individuals taking calcium supplements are at risk of developing phosphorus deficiency according to a report in the Journal of the American College of Nutrition (2002;21:239–44). Since phosphorus is an essential nutrient for bone formation, a deficiency of this mineral could lead to osteoporosis or might block the beneficial effect of calcium supplementation.
Researchers studied the effect of different levels of calcium intake on the absorption of phosphorus by healthy men and women between the ages of 19 and 78. They found that for each 500 mg per day increase in calcium intake the absorption of phosphorus decreased by 166 mg per day. For an elderly person taking 1,500 mg of supplemental calcium per day, that would translate to approximately a 45% reduction in the amount of phosphorus absorbed.
The main dietary sources of phosphorus are milk products, meat, and grains. In addition, a number of processed foods (particularly cola beverages) contain phosphate additives that provide absorbable phosphorus. Although most Americans consume 100% or more of the Recommended Dietary Allowance for phosphorus, older individuals often reduce their total food intake and consume less of the high-phosphorus foods. While these dietary changes may not by themselves be enough to cause phosphorus deficiency, supplementing with large amounts of calcium could lead to a phosphorus deficiency in people who are consuming marginal amounts of the mineral.
To prevent calcium-induced phosphorus deficiency, the authors of this study recommend that at least a portion of an older person's calcium supplementation be taken in the form of a calcium phosphate preparation (such as tricalcium phosphate), instead of the more commonly used calcium carbonate or calcium citrate. They point out that one of the most successful clinical studies of calcium supplementation in elderly people used tricalcium phosphate as the calcium source. Calcium phosphate products are commercially available (Posture®, for example), although they are not widely advertised.
Taking extra phosphorus is not appropriate for individuals who already consume large amounts in their diets. In fact, much of the research on phosphorus intake has focused on the problem of excessive phosphorus intake leading to a calcium deficiency. A dietitian or nutritionist can assess habitual intakes of calcium and phosphorus, and determine whether taking additional phosphorus would be desirable. Measuring blood and urinary levels of phosphorus might also provide a clue as to whether phosphorus intake is sufficient.
Alan R. Gaby, MD, an expert in nutritional therapies, testified to the White House Commission on CAM upon request in December 2001. Dr. Gaby served as a member of the Ad-Hoc Advisory Panel of the National Institutes of Health Office of Alternative Medicine. He is the author of Preventing and Reversing Osteoporosis (Prima, 1994), and co-author of The Natural Pharmacy, 2nd Edition (Healthnotes, Prima, 1999), the A–Z Guide to Drug-Herb-Vitamin Interactions (Healthnotes, Prima, 1999), Clinical Essentials Volume 1 and 2 (Healthnotes, 2000), and The Patient’s Book of Natural Healing (Prima, 1999). A former professor at Bastyr University of Natural Health Sciences, in Kenmore, WA, where he served as the Endowed Professor of Nutrition, Dr. Gaby is the Chief Medical Editor for Healthnotes, Inc.
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