Über die Autorin bzw. den Autor

Diane L. Schneider, MD, MSc, FACP (La Jolla, CA) is one of the country’s leading experts on bone health, at the forefront of important advances in this field. Her research has been published in the Journal of the American Medical Association (JAMA), Archives of Internal Medicine, and other prestigious medical journals. A former associate professor of clinical medicine at the University of California, San Diego School of Medicine, she is the co-founder of 4BoneHealth, a nonprofit organization focused on bone health awareness and education for the whole family.

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THE COMPLETE BOOK OF BONE HEALTH

Prometheus Books

Contents

Foreword by Sally Ride, PhD........................................................11Introduction: To Your Bone-Healthy Life............................................13FDA-Approved Medicines.............................................................171Drugs in Development...............................................................255Complementary and Alternative Medicine.............................................268After a Major Fracture.............................................................294Other Concerns.....................................................................311Acknowledgments....................................................................439References.........................................................................441Index..............................................................................481

Chapter One

Osteoporosis is truly a childhood disease. The problem with osteoporosis and fractures is that these do not occur until you are older. A misspent youth may place you at high risk for not only future fractures but for fractures as a preteen or teen. The window of opportunity to build the strongest bones begins during your mother's pregnancy and ends in your early adulthood.

You reach your skeletal maturity, called peak bone mass, by your late twenties to early thirties. Actually, the action occurs much earlier. For women, 90 to 95 percent of your peak bone mass is attained by age eighteen. This bears repeating: the majority of your bone mass is acquired by age eighteen. Men usually take a year or two longer to reach that level.

Think of your bones as your bank account or 401(k). You want to build up the balance as high as possible before you start making withdrawals. By age thirty you stop making deposits. Unlike a 401(k), the withdrawals start at a much earlier age. Penalties are accrued if you don't provide the supplies needed for bone maintenance.

The biggest drawback to reading this information now is that you are probably already older than thirty. But it is never too late to get on track with a bone-healthy lifestyle. Your bones require essential support every day. The basic tenets of bone health are true for your entire lifetime.

IT'S IN THE GENES

Building perfect bones begins with your mother and father: Your genes account for 60 to 80 percent of your potential adult bone mass. Lifestyle factors and sex hormones that kick in during puberty contribute the remaining 20 to 40 percent. While those percentages might sound discouraging, the good news is that you can make a difference of as much as 40 percent.

In addition, lifestyle factors may be underestimated when calculating the role of genetics. Environmental influences may affect the behavior of genes without altering DNA. Therefore, lifestyle choices play an important part in the way genes behave. This offers hope for people with a strong family history of osteoporosis. You should not hold a fatalistic attitude if you feel "doomed" by your family history.

IN THE BEGINNING: IS IT ALL OVER BEFORE IT BEGINS?

Growth of the skeleton is a complex process that begins in the womb and continues into early adulthood. Any problems during these years may result in reduced bone development leading to an increased risk of fracture later in life. Simply having poor vitamin D and calcium intake, or not maintaining a healthy weight during growth, can spell trouble in your golden years—or even earlier.

The first nine months, in your mother's womb, may shape the rest of your life, not just for your bone health but for your overall health. Calcium and vitamin D are required for development of the growing baby's bones. Addition of calcium starts midterm and increases in the third trimester, when the bones are growing rapidly. This corresponds to a daily calcium demand of about 250 to 300 milligrams (mg) during the third trimester. It is important that the mother's supply of nutrients is sufficient to match the baby's needs. The mother's absorption of calcium increases to meet the needs of the calcium transfer to her growing baby. Expectant mothers' calcium requirement is 1,000 mg a day. Higher levels of vitamin D supplementation may be required beyond the daily prenatal vitamins.

In one study, researchers found that low vitamin D levels in expectant mothers, measured in the third trimester of pregnancy, were associated with lower knee-to-heel lengths measured in their newborns at birth. In another study that followed about two hundred children from birth, lower bone mass at age nine was associated with their mothers' low levels of vitamin D in late pregnancy.

Low birth weight is associated with a higher risk of osteoporosis and other diseases, including heart disease. My patients were always surprised when I asked them for their birth weight. They thought it was a strange question. However, birth weight is correlated with the risk of fracture in later life. If you were a premature baby, you may have ended up with a smaller body size and smaller, less dense bones.

CHILDHOOD GROWTH

Immediately after birth, the rate of bone growth is high. Rapid growth occurs from birth to twelve months. Body mass generally triples and the growth in bone mass is similar. In the years between infancy and puberty, the most rapid growth in bone mass occurs from about ages one to four years. More rapid growth occurs in the bones of the arms and legs than in the trunk. Until puberty, bone mass is about the same in boys as in girls.

Genetic differences may have a role during this time period that explains much of the variability among different racial or ethnic groups. Some studies of Caucasian and African American children have found that bone mass is greater in African American children before puberty. Others observed that differences emerge in adolescence when African Americans gain more bone mass than Caucasians. Limited data from Asian and Hispanic youth show that their bone mass is similar to Caucasians or is intermediate between Caucasians and African Americans.

In the preteen years, the body begins revving up all of its systems for the rapid growth phase associated with puberty. At this stage, the skeleton of a preteen is more responsive to calcium, protein, and exercise than in later years. Young bones respond more to exercise than adult bones. Weight-bearing exercises are the most effective, particularly jumping and running.

PUBERTY: GROWTH SPURT

Growth hormones and sex hormones that kick in between childhood and puberty significantly alter bone mineral buildup. Peak bone growth lags behind peak height growth by approximately one year. Early prepuberty is the beginning of rapid bone growth. At puberty, with the secretion of sex hormones, growth of the trunk accelerates; the growth of the long bones of the arms and legs slows down until the growth plates fuse and linear growth stops.

Generally the growth spurt occurs between ages eleven and fourteen for girls and between thirteen and seventeen for boys. Forty percent of total adult bone mass is accumulated during these three to four years of rapid bone mass growth. The two years of peak skeletal growth occur approximately between the ages of eleven and a half and thirteen and a half for girls and...