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New Insights into Bone Strength
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James Offline

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New Insights into Bone Strength

New Insights into Bone Strength

by Bahram H. Arjmandi, Ph.D., R.D.

Osteoporosis is a debilitating disorder that affects both women and men, albeit to a greater extent in women. The postmenopausal period typically occupies one-third of a woman’s life, and more than 42 million women in the United States are currently postmenopausal. Although several drug therapies are available for osteoporosis, they are not free of risk or side effects. Furthermore, data on long-term use of drug therapies indicate patients’ compliance is low, and only a small percentage of patients are willing to be placed on drug therapy for an extended period of time.

Calcium and protein are the major components of bone tissue. Roughly 70 percent of bone tissue is made up of minerals, mainly calcium, and the rest is protein and water. Proteins affect bone in several ways, providing structural matrix of bone, optimizing insulin-like growth factor 1 and increasing intestinal calcium absorption while fighting urinary loss of calcium. Osteoporosis in postmenopausal women is often associated with intestinal malabsorption of calcium. In vitro studies have reported intestinal cells contain estrogen receptors, and estrogen directly enhances calcium absorption. Animal and human studies also support the in vitro findings of the role of estrogen in enhancing intestinal calcium absorption. Although calcium is an essential component of bone, it is a threshold element and exceeding the recommended level may not be of benefit to skeletal health.

In terms of protein, there are a few reports that indicate animal protein-based diets might have a deleterious effect on skeletal health due to the high sulfur-containing amino acids, which leads to increased urinary excretion of calcium. This might be the basis for reports indicating consumption of a diet rich in soy may be superior to animal proteins for bone health. Interestingly, more recent findings suggest higher protein intakes are linked to higher bone mass when calcium intake is adequate. This is one reason for the recommendation of increased protein along with calcium intake for the elderly. Dietary protein, especially from animal sources, may increase metabolic acidosis, causing release of calcium from bone to alkalize the acidic environment, causing further loss of urinary calcium. It was first reported in 1988 that replacing casein in a diet of 18-month old rats with soy not only resulted in the rats’ not losing bone, but also living longer. In 1996, our lab reported soy protein isolate, when replacing casein in the diet of ovariectomized rats, prevented bone loss. Nonetheless, after more than a decade of studies as to the effectiveness of soy and its components in term of bone, it appears the bone protective effects of soy protein are related to the protein itself rather than its isoflavones. This view is confirmed by recent findings that soy isoflavone treatment of healthy postmenopausal women for three years had only modest beneficial effects on mid-shaft femur volumetric bone mineral density (vBMD).

Another source of protein used for centuries to address health issues including joint pain and bone improvement is gelatin, which is a partially hydrolyzed collagen derived from animal sources. For instance, clinical trials have shown oral administration of cartilage-derived type II collagen can improve the symptoms of rheumatoid arthritis (RA), which may be due to gelatin’s direct analgesic effect. Another study reported administration of pharmaceutical-grade collagen hydrolysate plus calcitonin decreases the breakdown of bone collagen in postmenopausal women, which may be due to the fact that gelatin-containing products increase the pool of amino acids in the body. Furthermore, recent findings suggest a calcium-collagen chelate is highly effective in modulating bone mass in rat models of osteoporosis. Preliminary data suggest calcium collagen chelate significantly increases total BMD in postmenopausal women by increasing bone formation and suppressing bone resorption.
02-05-2013 02:15 AM
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