Your Biggest Supporters: Healthy Bones

Human engineering can rightfully claim some brilliant successes when it comes to materials, from the metals and alloys of antiquity to the remarkable composites found in space craft. But we’ve never succeeded like bone has. Our bones not only bear the body’s weight and enable a remarkable range of flexible movement, it stores minerals, protect internal organs, and, in its spongy interiors, produces our very lifeblood.

Bone is a building material so malleable it can be fashioned into any shape, so flexible it can bear more weight and withstand greater stress or compression than any human-made construction material, and so strong it can meet the 24/7 demands of human activity for 75 years or more.

But beyond all of the impressive technical specs of bone, of course, what’s truly stunning about the design of bone is that it is alive. The skeleton breaks down and renews itself continually. As our bodies grow from infancy into adulthood, our frames adapt their shapes and proportions to match the demands of maturation. And when bones break, they knit themselves back together again. LESS

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Throughout a person’s lifetime, old bone is constantly being broken down and replaced with new bone to maintain a healthy bone structure. During the breakdown of bone (resorption), cells called osteoclasts dissolve the mineral protein matrix. Bone formation is managed by cells called osteoblasts, which produce the components that help form a new protein network, which is in turn re-mineralized with calcium and phosphate. This on-going demolition and construction process is constantly taking place on a microscopic scale throughout the body.

Balance between the two processes is essential for bone health. From infancy through young adulthood, new bone is added faster than old bone is removed. Bone mass peaks between the ages of 25 and 30 years; after that, bone loss outpaces bone formation, leading to net bone loss. Bone loss is most rapid in women in the first few years after menopause; in men, noticeable bone loss does not usually occur until after age 70.

Bone mineral density (BMD) is the standard measure of the mineral content and mass of bone tissue. The loss of bone mineral density is called osteopenia, and when it continues, osteopenia leads to osteroporosis and bones become weak, brittle and prone to fracture. Half of all women and a quarter of men will break a bone after age 50 due to osteoporosis. (A statistical tool called FRAX can help individuals estimate their risk of suffering fractures of the hip, wrist, shoulder, or spine after age 40.)

Women are significantly more likely to develop osteopenia and osteoporosis than men. This is because women have lower bone mineral density than men even when young, and because a woman’s hormonal changes at menopause hastens bone mineral loss.

According to the National Osteoporosis Foundation (NOF), an estimated 10 million Americans already have the disease and 34 million have low bone density, placing more than half of adults age 50 and older at risk (80% are women). The NOF recommends screening for men over 70 and women over 65, as well as younger adults who are at risk.

Bone health is tested for a variety of reasons, but the most common reason is to identify individuals who have or are at risk of developing osteoporosis and to monitor treatment of the disease. There are several blood tests used to assess bone health. Scanning and imaging technologies are also used to measure bone mineral density, including X-rays, CT scans (computerized tomography), and ultrasound. LESS

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Vitamin D plays a critical role in bone health by regulating the absorption of calcium, phosphorus, and magnesium; it is also a hormone essential for muscle, nerve and immune system function. There are few foods naturally rich in vitamin D (oily fish are the exception), which is why this essential vitamin is added to milk and cereals. Vitamin D is also produced by skin cells in the presence of sunlight. Our ability to produce this vitamin in our skin declines after age 40, however; by age 70, our skin can produce only half as much as it could at age 20.

A deficiency of vitamin D can result in soft, malformed bones in children (rickets) or weak bones easily fractured in adults (osteomalacia). Too much vitamin D is nearly always the result of taking supplements (there are a few exceptions); high levels of vitamin D and calcium can lead to calcification and damage to blood vessels and organs, such as the kidneys.

Recently, however, vitamin D has stepped beyond its role as calcium’s co-star in milk. Researchers are finding evidence that this essential hormone may also be linked to cancer, immune function, heart disease, and diabetes, as well as cognitive impairment. The possibility that vitamin D is even more important than once thought has many medical experts concerned; some studies suggest that half of the world’s population has inadequate blood levels of vitamin D. LESS

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