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Is there a point in life when bones peak in density?

Throughout the first few decades of human life, and providing that adequate minerals are provided by diet, the body deposits these minerals into bone in order to strengthen it and also to serve as a future mineral reservoir. Humans typically reach peak bone mass (PBM) or maximal bone density (MBD) by their late twenties to very early thirties. After this time, bone density seems to decrease slowly. From a osteoporosis prevention standpoint, maximizing peak bone mineralization or maximal bone density is crucial!

How much bone is lost as osteoporosis develops?

The decrease in bone density appears to be more substantial in women versus men. It has been estimated that a woman may lose 27 percent or more of her bone mineral from peak bone mass to her seventies. Bone mineral losses of up to 50 percent have been reported in women diagnosed with osteoporosis. The point should again be made that while the focus has largely been on minerals, osteoporosis is a disease resulting from loss of bone material in general. This means that protein as well as minerals are lost, and as mentioned above, some researchers believe that the key to preventing osteoporosis may actually be founded in preserving (and rebuilding) the collagen foundation. Without collagen, the minerals could not stick in bone. Perhaps the analogy of hanging drywall on the wooden frame of a house will help. Here the wooden frame is collagen and the drywall is hydroxyapatite. In fact, hydroxyapatite crystals resemble sheets of drywall (see Collagen and Hydroxapatite Figure).

How is estrogen involved in the loss of bone mineral?

A reduction in blood estrogen levels, as typical after menopause (postmenopausal), is directly associated with a decrease in bone den­sity. Thus, estrogen is a principal factor in the development of osteoporosis. Researchers have reported that osteoblasts (bone makers) have receptors for the hormone estrogen, and estrogen also appears to decrease the activity of osteoclasts (bone destroyers). Despite these findings, the exact mechanisms for how estrogen protects women against excessive bone material losses is not clear. Postmenopausal estrogen replacement therapy (ERT) has proven effective in slowing the rate of postmenopausal bone mineral loss in women however there are other medical concerns and each women should understand these.

What nutritional and behavioral factors are important in preventing osteoporosis?

Beyond reductions in circulating estrogen in postmenopausal women, other factors can increase the loss of bone mineral. These factors include poor calcium and/or vitamin D intake as well as abnormalities in metabolism. Smoking seems to exert a negative influence upon bone mineral content and the rate of bone mineral loss, especially in postmenopausal years.Smokers tend to have lower bone densities than nonsmokers. One reason for this occurrence is that smoking reduces blood estrogen levels. Also, smokers also seem to reach menopause at a younger age.

Additionally, physical activity increases the mechanical stress placed on bone and stimulates a reinforcement of bone strength. Perhaps this effect is most obvious in the absence of any weight-bearing demands upon bone. For instance, astronauts subjected to extended periods of time in space at zero gravity (weightlessness) experience decreases in bone density. On the other hand, regular weight-bearing exercise seems to help strengthen bone and also to slow the gradual loss of bone material as the body ages.

Can osteoporosis occur earlier in life?

Although osteoporosis is most often diagnosed in postmenopausal women, it should be noted that signs of osteoporosis have been observed in younger women as well. Younger female athletes who are excessively lean can reduce or halt their estrogen production and establish the opportunity for bone loss. In addition, the positive effects of weight-bearing exercise are not apparent in excessively lean women. The positive effects of resistance training will not balance out the negative impact of reduced estrogen levels. Anorexia nervosa, which is most common in teenage and younger adult women, is characterized by abnormally low body weight. This state can also reduce estrogen production and invoke bone demineralization.

What are the most conventional ways to prevent osteoporosis?

The best defense against osteoporosis is a good offense. Some weight-bearing exercise and a diet (with supplementation) providing adequate protein, vitamin D, calcium, magnesium, boron, zinc, vitamin C, copper, and iron in the years prior to peak bone mass will optimize bone density. The latter minerals and vitamin C are important for making proper collagen. An early start and a continuation of these practices throughout adulthood in conjunction with regular medical checkups and a periodic X-ray will provide the most benefit. In fact, it seems that one of the most important times for the positive effects of activity on bone density is during the pre-puberty years. Children should be encouraged to be involved in physical activities. Also, discuss menopausal/post­menopausal hormone replacement therapy with a physician; and do not smoke and encourage others to quit as well.

Can soy help prevent osteoporosis?

Some of the most promising nutraceutical substances in the prevention of osteoporosis are isoflavones found mostly in soybeans and soy foods (tofu, tempeh, and miso). There are about twelve forms of isoflavones in soy, including genestein and daidzein. Researchers believe that these factors may have the ability to bind to estrogen receptors and that would include those in bone tissue. At this time scientists are optimistic that a positive link exists between soy or iso­flavoneconsumption and bone health. However, it will probably take time and a few well-performed human studies to draw more specific conclusions. So at this time it would seem wise to include some soy in the diet.

Can caffeine or coffee cause osteoporosis?

The results of a couple of studies revealed a correlation between excessive coffee consumption and a higher hip-fracture rate. However, even if there is a true effect many researchers believe that there is a safe level of consumption. It does seem that one to three cups of coffee a day probably does not factor into the development of osteoporosis.

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