Friday, July 23, 2010

Preventing osteoporosis: Establish a foundation


By Dr. DANIEL B. JUDD

In the United States, an estimated 1.5 million individuals sustain a fragility fracture secondary to osteoporosis each year. Fragility fractures refer to certain vertebral, hip, and wrist fractures that occur with minimal or sometimes no trauma, and are a result of a generalized decrease in bone mass and deterioration of bone strength.

Bone mass increases with age until approximately 30 years. After this peak, there is a slow decrease in bone mass each year in both males and females. In females, the loss in bone mass is accelerated after menopause due to a drop in estrogen level. During the post-menopausal period, there is a 1-3 percent decrease in bone-mineral density per year, for as long as 10 years. This progressive decrease in bone mass and loss of bone strength can lead to fragility fractures.

What can be done to optimize bone health and decrease the risk of fragility fractures?

Genetics plays the major role in determining one's ultimate bone mass. However, there are certain factors under our control that contribute to bone health and substantially decrease one's chances of sustaining a fragility fracture—nutrition and physical activity.

The foundations of adult bone health are established during youth. Therefore, optimization of bone health during childhood and adolescence is essential. As with many things, a balanced, well-rounded diet with ample fruits and vegetables is fundamental, but three important players in bone health will be highlighted: physical activity, calcium, and vitamin D.

Physical activity: Bone is biological tissue and adapts according to the level of loading it experiences. Several studies have found beneficial effects of physical activity on bone health in children and adults. Children involved in exercise have a higher bone mass than children who do not exercise. Furthermore, in response to weight-bearing exercises the bone undergoes structural adaptations, increasing in circumference and area. Studies have suggested that the gains in bone strength that children and adolescents obtain from physical activity last into adulthood. Adults need to continue weight-bearing activities, as the positive changes in bone health are lost once regular exercise is stopped.

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Calcium: Calcium is the most abundant mineral in our bodies, and approximately 99 percent of it is found in our teeth and bones. The remaining calcium plays crucial roles in maintaining cellular structure and metabolic functions. The calcium in our bone is found in the form of hydroxyapatite crystals and contributes to its strength. Thus, optimal bone health depends on adequate calcium. The National Osteoporosis Foundation recommends a daily calcium intake of 1000 mg per day under the age of 50, and 1,200 mg per day over the age of 50. Supplementation, preferably in the form of calcium citrate, is recommended if dietary intake is inadequate.

Vitamin D: Vitamin D influences many organ systems, and insufficient vitamin D has been associated with multiple medical conditions. In terms of bone health, vitamin D plays an important role in promoting calcium absorption from our diet and stimulates bone formation.

Growing evidence suggests that mild vitamin D insufficiency in adolescent females puts them at risk of not reaching their maximal potential bone mass. For example, in a Finnish study of girls 9-15 years old, comparing differences in peak bone mass between subjects with very low vitamin D levels, to subjects with normal levels, there was a 27 percent higher bone-mineral density in the subjects with normal vitamin D levels. Further studies in elderly adults have found reductions in fragility fractures in individuals who received 700 to 800 International Units of vitamin D per day, compared with individuals who received 400 IUs.

Vitamin D can be obtained from diet and sun exposure to the skin without sunscreen. Recommendations for the duration of sun exposure vary, and depend on the sun intensity, but 10 to 15 minutes of sun exposure to the hands and arms two to three times a week is thought to be adequate. The efficiency of vitamin D synthesis decreases with age and other factors, so dietary intake is important. Most current recommendations suggest the minimal adult intake to be above 800 IUs.

In a nutshell, fractures secondary to osteoporosis are a significant health concern. Fortunately, there are choices we can make to lessen our risk and help us remain mobile and injury free.

Dr. Daniel B. Judd works at St. Luke's Sun Valley Sports Medicine.




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