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.

Vitamin D: A Developing Story

Ten years ago, it is unlikely that vitamin D was on your list of things to worry about.  Now you probably know someone who is vitamin D – deficient and taking a vitamin pill every day – or at least during the winter months when the sun is low in the sky. Finding a magazine or newspaper that hasn’t published stories warning about deficiencies in the “sun vitamin” is difficult. What happened?  Do we have a new problem, or have we just learned more about an old one?

The magic ingredient in cod liver oil

The old part of the Vitamin D story is about a childhood disease called rickets and an adult version of rickets called osteomalacia. Both afflictions became common when urbanization crowded people into the sooty cities of northern Europe in the 1700s. Affected children had bowed legs, malformed chests and teeth, weak muscles and easily fractured bones. In adults, whose bones had stopped growing, the symptoms were bone pain, fractures, and muscle weakness. Though folklore from coastal cities had long described cod liver oil as a remedy for these problems and for other rheumatic complaints, it wasn’t until the early 20th C that scientists discovered that the magic ingredient in cod liver oil was one of the newly described vitamins- special compounds the body can’t make but needs to get in small amounts from specific foods. Vitamin D was the fourth one named, after Vitamins A, B, and C.

Further research demonstrated that Vitamin D is present in many animal fats, and is necessary for the transport of calcium from the intestine into the blood. The rampant rickets and osteomalacia of the early industrial revolution years seemed accounted for by poor diet, but the concentration of these problems in northern climates prompted more questions.  The answers started a new chapter in the story of Vitamin D—its relationship to the sun and its reclassification as a hormone rather than a vitamin.

Vitamin D is actually a hormone, not a vitamin

Vitamin D, as demonstrated by an elegant series of experiments in the 1920s, can be made by the body, in the skin —as long as the skin is exposed to sufficient sunlight. By the time of this discovery though, the vitamin label was too well established to be removed. What started out being known as the bone vitamin became the sunshine vitamin, and more research into its biochemistry placed the “vitamin” firmly in the camp of the  hormones, which are made in the body’s glands and and which act on many different and distant parts of the body to signal changes in cellular functions. Chemically , Vitamin  D most resembles steroid hormones such as testosterone and cortisol and estradiol.

The discovery of Vitamin D receptors

Vitamin D research took its next leap when hormones were discovered to have receptors in the tissues where they were active. Sure enough, Vitamin D had receptors too, in virtually all tissues. By the 1990s researchers were busy trying to find out why. They observed that vitamin D suppressed the growth of cancer cells – at least in the laboratory. Statistical studies showed lower cardiac death rates in the people with the highest vitamin D levels. The bone vitamin suddenly had many possible functions.

In the last decade thousands of studies have attempted to relate hosts of medical problems to vitamin D deficiency, including autism, depression, dementia and other neurodegenerative diseases, many varieties of musculoskeletal pain and arthritis, and autoimmune diseases like multiple sclerosis. So far, most of the research implies that vitamin D exerts its effects in a variety of tissues over the long term, altering the way genes are expressed rather than acting rapidly and directly as it does in intestinal transport of calcium.

Deciding who is deficient in D

Nevertheless, the race is on to see whether or not vitamin D might help many of the ailments that plague us. The first step is trying to decide who is deficient. Measurements of vitamin D, which is a general term applied to a number of different forms of the vitamin, were not standardized until 2006. There is still sometimes contentious debate about which form of the vitamin to measure and what constitutes a normal level.  The general consensus is that vitamin D3 (1-hydroxycholecalciferol) is the best measure of the body’s stores of vitamin D.  The range of normal values of vitamin D3 comes from studies of healthy Hawaiian surfers, who rarely have levels below 30 nanograms (ng)/ml and rarely above 60 ng/ml.  Different laboratories sometimes cite different values, but generally a value in the 20-30 range or lower indicates deficiency.

Requirements change with age

Requirements for vitamin D vary and change over life. As people age, skin produces less. Darker skinned people make less vitamin D. The recommended dose of vitamin D supplements is 200 IU/day (5 micrograms), 400 IU after age fifty, and 600 IU after age 70. Research enthusiasts suggest more.  Sun exposure is by far the most efficient route to adequate vitamin D. Twenty minutes of face and arm exposure produces as much as 10,000 IU vitamin D, which is stored efficiently for weeks. Most supplements are made from the skin of animals or derived from plants chemicals exposed to UV light. (Plant derived vitamin D is known as vitamin D2.)

Rickets makes a comeback

Are we more in need of vitamin D now than previously? In the past, we looked for vitamin D deficiency only in obvious cases of bone disease and kidney failure (the kidney converts vitamin D3 to its most active form). But now, with the best of intentions, we may have created another version of the sunlight deficient, dietary-restricted cities where rickets once thrived. We assiduously shun fat, meat, dairy products and eggs to avoid cardiac disease.  We apply sunscreen liberally to avoid skin cancer. Rickets is on the rise, there are more pediatric bone fractures than in there were a few decades ago, and general arthritic complaints abound. And we now suspect vitamin D may be required for basic cell functions in all organs.

What to do?

A little unprotected sun exposure every few days, and judicious intake of eggs, milk, fatty fish – even a little cod liver oil now and then –  are reasonable tactics to increase the body’s Vitamin D production . Or you could ask your doctor to check a vitamin D blood level and consider taking a supplement if the level is low, especially if you spend the winter above the latitudes of Boston and the California/Oregon border.

 

                                                    Food Sources of Vitamin D

                                      (From NIH Office of Dietary Supplements)

                                                                                                                                                                                                                                                                                                                                                                       IU         %RDA

Cod liver oil*, 1 tablespoon                                            1,360         340

Salmon (sockeye), cooked, 3 ounces                             794         199

Mackerel, cooked, 3 ounces                                              388           97

Tuna fish, canned in water, drained, 3 ounces            154           39

Milk, vitamin D-fortified, 1 cup                                  115-124    29-31

Yogurt, fortified, 6 ounces                                                  80            20

Margarine, fortified, 1 tablespoon                                    60             15

Sardines, canned in oil, drained, 2 sardines                  46             12

Beef liver, 3.5 ounces                                                             46             12

Fortified ready-to-eat cereal, 0.75-1 cup                        40            10

Egg, 1 whole (vitamin D is in yolk)                                     25              6

*The problem with cod liver oil as a source is that Vitamin A tags along and Vitamin A can be toxic in high doses, producing brain swelling. Check the source information and composition.

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