Osteoporosis: Nutritional Considerations
Osteoporosis is a common disease in areas where Western diets prevail. The common belief that this complex disease is preventable or treatable by a high intake of calcium supplements or dairy products has not withstood scrutiny.8 The Nurses’ Health Study, following more than 72,000 women for 18 years, found no effect of either dairy products or a high–calcium diet on fracture risk.9 Skeletal health involves dietary habits that support bone formation and retard bone resorption, in addition to regular exercise. For some, a combination of drug therapy and supplemental approaches may be required as well. The topic of daily calcium intake and its impact on bone metabolism remains highly controversial.
The following factors are under investigation for their role in preventing or slowing osteoporosis:
Reduced animal protein intake. Cross–cultural studies have found strong, positive relationships between animal protein intake and risk for hip fracture.10 Higher meat intake (> 5 servings per week) significantly increased the risk for forearm fracture in women, compared with eating meat less than once per week.11 Elderly women whose diets contain a high ratio of animal to vegetable protein have more rapid bone loss and greater risk for hip fracture than those with a low ratio.12 Bone health appears to benefit from replacing animal protein with vegetable sources of protein, particularly soy. In clinical studies with postmenopausal women, soy foods have been found to prevent bone loss.13 Other research has found a dose–response relationship between soy protein and bone mineral density in postmenopausal women.14 The relatively high concentrations of isoflavones in plant–based proteins may be one of the many proposed reasons for their beneficial effect on bone metabolism.15
Increased fruit and vegetable intakes. Studies have shown that fruit and vegetable intakes are associated with bone mineral density in both women and men. These associations may be due to the buffering effect of potassium and magnesium in fruits and vegetables on the acid–base balance that partly determines bone resorption.16,17 These foods also provide vitamin K, low intakes of which may contribute to osteoporosis and risk of hip fracture by causing undercarboxylation of osteocalcin.18,19
Reduced sodium intake. Some studies have found that habitually high sodium intake increases urinary calcium loss20 and markers of bone resorption.21 Although restricting dietary sodium reduces calcium loss and markers of bone resorption in post– (not pre–) menopausal women,22 the effect of sodium restriction on long–term bone integrity and fracture risk remains unclear.
Low–fat diets. Studies have found that higher intake of fat is associated with a greater loss of bone2 and greater fracture risk.23 Possible mechanisms include the tendency of excess fat intake to reduce calcium absorption and to affect eicosanoid production. Specifically, the omega–6 polyunsaturated fatty acids linoleic acid and arachidonic acid act as precursors to prostaglandin E2 (PGE2), which favors osteoclast–induced bone resorption at the expense of osteoblast–induced bone formation.24
Moderation in caffeine use. Studies have found that women consuming the most caffeine have accelerated spinal bone loss25 and almost triple the risk for hip fracture.26 The risk for bone loss appears to be greatest in women who consume > 18 ounces of coffee per day, or 300 mg caffeine from other sources.
Limiting supplemental vitamin A. Studies have shown that the declines in bone density and risk for hip fracture are increased at as little as twice the recommended intake for retinol.27 Risk for fracture also appears to be significantly higher in women consuming more food sources of retinol.28 Vitamin A adequacy can instead be ensured with beta carotene from plant sources, particularly orange and yellow vegetables.
Combined supplemental vitamin D and calcium. The effect of a combination of these 2 nutrients appears to be of significant benefit in reducing bone loss in patients with corticosteroid–induced osteoporosis.29 Supplements of vitamin D (500–800 IU/day) and calcium (1200–1300 mg/day) have also been found to increase bone density and decrease bone turnover and fracture risk in older adult women.30
Low sodium diet.
Restrict caffeine and alcohol consumption.
Female patients with osteoporosis should aim for a total calcium intake from diet and supplements of about 1500 mg/day in 3 or more divided doses, plus at least 100% of the dietary reference intake (DRI) for vitamin D (400–800 IU/day). While supplemental calcium and vitamin D may benefit selected adult patients without osteoporosis, no theoretical basis exists for population wide recommendations for high calcium intakes, particularly in males, due to associations between calcium or dairy intake and prostate cancer (see Prostate Cancer).
Exercise prescription with patient–appropriate, weight–bearing exercises. Physical therapy or exercise physiology consultation as needed.
What to Tell the Family
Osteoporosis is a preventable and treatable disorder. Proper dietary and exercise habits help maintain bone integrity and reduce bone loss later in life. The osteoporosis patient should limit alcohol and caffeine to <1 serving per day and restrict salt intake in order to limit the calcium losses these substances may cause. Medications may help adjunctively to reduce bone loss, improve bone density, and reduce fracture risk.
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