Osteoporosis: Nutritional Considerations

Osteoporosis is a common condition in areas where Western diets prevail. It was once commonly believed that osteoporosis could be prevented by high intake of calcium supplements or dairy products; however, clinical studies have shown that this is not the case. The Nurses’ Health Study, which followed more than 72,000 women for 18 years, found no effect of either dairy products or a high–calcium diet on hip fracture risk.

The following factors are under investigation for their role in preventing or slowing osteoporosis:

• Reduced animal protein intake: Animal protein increases calcium losses. Cross–cultural studies have found strong relationships between animal protein intake and risk for hip fracture. Higher meat intake (five or more servings per week) significantly increased the risk for forearm fracture in women, compared with eating meat less than once per week. Elderly women who eat a significant amount of meat have more rapid bone loss and greater risk for hip fracture.
  
  Risk of bone problems appears to diminish when animal protein is replaced with vegetable sources of protein, particularly soy. In clinical studies with postmenopausal women, soy foods have been found to prevent bone loss. Research has shown a positive relationship between soy protein and bone mineral density in postmenopausal women. This may be due to the relatively high concentrations of compounds called isoflavones in plant–based proteins.
• Increased fruit and vegetable intakes: Studies have shown that diets rich in fruits and vegetables are associated with higher bone mineral density in both women and men. These associations may be due to the potassium, magnesium, and vitamin K in fruits and vegetables.
• Reduced sodium intake: Some studies have found that high sodium intake results in the loss of calcium from the body. However, the effect of sodium restriction on long–term bone integrity and fracture risk remains unclear and requires further study.
• Low–fat diets: Studies have found that higher fat intake is associated with a greater bone loss and greater fracture risk. Possible mechanisms include the tendency of excess fat intake to reduce calcium absorption and to affect hormone production. Specifically, the omega–6 fatty acids can result in bone loss at the expense of new bone formation.
• Moderation in caffeine use: Studies have found that women consuming the most caffeine have accelerated spinal bone loss and almost triple the risk for hip fracture. The risk for bone loss appears to be greatest in women who consume more than 18 ounces of coffee per day, or 300 mg caffeine from other sources. 
• Limiting supplemental vitamin A: Studies have shown that too high intake of vitamin A, either by food or supplements, can cause decreased bone density and increased risk for hip fracture. A healthful and sufficient intake of vitamin A can be ensured with beta–carotene from plant sources, particularly orange and yellow vegetables. 
• Combined supplemental vitamin D and calcium: In patients with medication–induced osteoporosis, a combination of these two nutrients appears to be of significant benefit in reducing further bone loss. Supplements of vitamin D (500 to 800 IU/day) and calcium (1200 to 1300 mg/day) have also been found to increase bone density and decrease bone loss and fracture risk in older adult women.
  
  Female patients with diagnosed osteoporosis should aim for a total calcium intake from diet and supplements of about 1500 mg/day in three or more divided doses, plus at least 400 to 800 IU of vitamin D daily. However, patients who are not at high risk for osteoporosis probably do not require calcium supplementation. This is particularly true for males, who may have an increased risk for prostate cancer if they consume too much calcium or dairy.