Thin Bones

Osteoporosis is an equal opportunity disease. Everyone is at some risk for age- related thinning of the bones. Prevention is the best treatment, and understanding how osteoporosis happens is the key to prevention.

Bone is alive

Bone may resemble concrete, but it is vibrant, living tissue that is perpetually under reconstruction. From the time of birth, when bones are composed mostly of soft, pliable cartilage, they shape and reshape themselves. Cells called osteoblasts appear in the cartilage and begin to lay down a protein matrix, spinning it into flexible tendrils like fine rope. A mixture of minerals, mostly calcium and phosphorus, hardens the matrix, creating the blend of strength and flexibility needed for the forces the skeleton has to bear. Throughout life the bones restore, remodel and repair themselves in response to the stresses of life on a planet governed by gravity.

Bones are storage depots for calcium

The bones also store calcium for the rest of the body and respond to its constant demands for the mineral. Cells called osteoclasts break bone down to free calcium for use elsewhere, and to remodel bone where changes are needed. So there is a constant interplay of bone construction and bone destruction throughout life, with the material of you skeleton renewing itself completely every ten years or so.

Bones build, remodel and breakdown

In youth, bone construction goes full blast. Once maturity hits, the process evens out. In older age, breakdown begins to exceed construction. Just another sign of inevitable decline? Yes, but don’t give up hope. You control some things that influence how fast bone loss occurs, and science is making strides to help.

You are the general contractor

You are in charge of the building material that your bones use. A healthy balance of food, including protein, fat, calcium and Vitamin D makes healthy, well-mineralized bones. You need 1200 milligrams of calcium a day, the amount in about three glasses of milk, and 400 IU of Vitamin D, which is made in the skin when it is exposed to sunlight (10-15 minutes of sun on hands arms and face, or back, twice a week). Vitamin D deficiency is common in the elderly because of indoor lifestyles, and in northern climates. Many foods are fortified with Vitamin D, and cod liver oil and fish are excellent natural sources.

Childhood habits matter

The bone density that you achieve in youth is important because it is the starting point for the gradual losses that come later. Maximal bone density for life is achieved in the early twenties The generations of children that have opted for pop over milk are at a disadvantage, arriving at adulthood with less calcium than past generations have.  and pediatricians are already seeing more children with fractures than in the past. The cost of neglecting childhood nutrition is bound to rise as time passes.

Gravity and exercise matter

You are also in charge of the activity that stimulates bone formation. When you are upright and fighting gravity, the osteoblasts lay down more bone matrix where it is needed to bear weight, particularly in the pelvis, lower spine and hip. But as soon as the stresses diminish, the osteoclasts start their breakdown work. Just a few days of bed rest sets them in motion. Astronauts in the space lab, under minimal gravity, lose as much bone in a month as a post- menopausal woman loses in a year. Even the impaired movement of a bone under a cast causes localized osteoporosis.

The more you exercise against gravity – as in walking, running, doing yoga or calisthenics, or weight lifting – the more you will call osteoblasts into action. Sit out life, and your osteoclasts will dominate.

Who does osteoporosis affect?

Youth compensates for deficits in diet and activity, but as growth-related hormones fall with age, the cost comes due.  Genetic makeup counts too. Women lose more bone than men, smaller-framed people more than larger-framed people, and Caucasians,and Asians more than dark-skinned people. Smokers and heavy drinkers are also at higher risk for osteoporosis, as are people who are confined to bed or taking steroid medications.

The cost of thin bones

Thin bones break and fractures are costly, about $10 billion for the 1.5 million fractures a year in the USA. Spinal fractures, the most common breaks, are very painful and cause spinal deformity and loss of height. Of all the people who fracture hips, 50% are permanently disabled, and twenty percent are dead within a year, from the consequences of immobility. This mortality rate is even greater in men, who are 20% of the 44 million people who have or are at risk for osteoporosis.

Prevention of  osteoporosis and fractures

The best treatment for osteoporosis is prevention, starting in childhood. Prevention means solid diet and habitual weight bearing exercise throughout life, and, as the risk of falling increases, exercises to maintain speed and balance. Canes, walkers, hip protectors (padded garments worn over the hips), and attention to the living environment (clear walkways, even surfaces, handrails, etc.) are forms of external prevention.

The role – and the problems – of pharmacologic attempts at prevention

Doctors often recommend bone density tests and sometimes they prescribe drugs to slow the loss of bone. At menopause, bone loss accelerates, and estrogen supplements for a few years have been common practice. Newer drugs such as Evista mimic estrogen’s effects on bone alone and may be safer than the older hormone supplements, which are associated with increased risks of strokes and some cancers, especially when used for many years. The biphosphanates, like Fosamax, slow the work of the osteoclasts by attaching to bone to block breakdown. But they bond to the bone and cannot be released. Some unusual and serious side effects such as sudden, unprovoked leg bone fractures and death of jaw bone after dental procedures. Fortunately these have been fairly rare occurrences.   Calcium and Vitamin D supplements improve bone-building supplies, but calcium absorption is not as good from pills as it is from whole foods, and sunlight exposure produces much more Vitamin D than pills can provide. More severe osteoporosis warrants more unusual treatments like shots of calcium-regulating hormones.

You job

Your skeleton will outlast you. Your job is to do your best to make sure it supports you while you are here, and to pass the word to the younger generations who are still building their bones.

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