Lenore S. Greenstein: Protein and its relationship with osteoporosis

Protein is critical in keeping our skeleton strong, yet it also has been regarded as harmful for bone health. Too much protein in the diet, particularly purified proteins found in powders and supplements, can lead to increased calcium excretion. This loss of calcium may cause a negative calcium balance, leading to bone loss and eventually to osteoporosis. In a recent study, women who consumed a high protein diet from food sources only, such as meat and milk, did not excrete excess calcium in their urine, nor were their bones adversely affected.

Findings from many studies point to a beneficial role for dietary protein and bone health. In fact, higher protein intakes have shown to reduce bone loss and fractures in older adults, and increase bone mineral density. Conversely, a low intake of protein has been linked to a decrease in bone density or frail bones, and a greater risk of fracture in older adults. In a recent clinical trial, increasing protein intake in subjects whose usual protein allowance was small, helped reduce bone loss, improved muscle strength, and shortened the hospital stay in older patients with hip fractures. This was especially true when the protein source was accompanied by calcium and vitamin D.

The current Recommended Dietary Allowance or RDA for protein is 0.8 grams of protein per kilogram of body weight (1 kilograms = 2.2 pounds), which translates into 46 grams of protein a day for women, and 56 grams a day for men, based on the average reference male or female body weight of 125 pounds and 154 pounds respectively. Many Americans consume far more protein than these recommended amounts. At the same time they may also eat diets that are rich in protein, but poor in calcium. New research suggests that protein in the diet acts synergistically with calcium to increase bone strength and density. The exception is the elderly elderly population, who may eat much less food due to loss of appetite, medications and other factors.

In a three-year prospective trial of more than 30,000 postmenopausal women who participated in the Iowa Women's Health Study, a higher protein intake, particularly animal protein, was associated with a 70 percent reduction in hip fractures. Similarly, a four-year follow-up study of older men and women from the Framingham Osteoporosis study, showed that eating more protein was associated with increased bone density in the neck and spine.

A number of other studies have demonstrated the intake of dairy products and other protein foods that are rich in calcium are unique in keeping osteoporosis at bay. They also contain other bone-supporting nutrients such as phosphorus, magnesium, zinc and vitamins A, D and K. Because protein doesn't exist alone in the diet, it is important to evaluate your overall food intake, and if necessary include more protein with good sources of calcium to match.

Lenore S. Greenstein is a registered and licensed dietitian in private practice in the Naples area.