Get the facts on: bone health basics; risk factors for bone loss and fractures; bone density "DXA" scans; exercise and nutrition; vitamin D; prescription medicines; controversial "hot topics"; complementary and alternative approaches; and common health problems and medicines affecting your bones.
Designed to be practical and user-friendly, each chapter ends with a bottom-line summary, "The Bare Bones," allowing you to easily reference issues of interest. This book is a clear, accurate, and up-to-date guide to improving bone health and contributing to a healthier life.
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About the Author
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
By DIANE L. SCHNEIDER
Prometheus BooksCopyright © 2011 Diane L. Schneider
All right reserved.
Chapter OneBuilding Perfect Bones: Timing Is Everything
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.
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 between thirteen and fifteen for boys. However, changes follow maturity levels rather than exact chronological age. Bone mass approximately doubles between the onset of puberty and young adulthood, and it increases more in boys than in girls. The larger bone size in boys is probably a result of boys having a longer period of accelerated growth.
The increase in bone mass is primarily due to an increase in bone size with little or no change to the amount of bone tissue within the bones. This is what creates the increased risk of fracture during the puberty years.
These preteen and teenage years represent a critically important window of opportunity to build bones that are as strong and dense as possible. Illness in prepuberty or puberty may interrupt growth. The end result will be lower bone mass.
At the end of bone growth, individuals of the same age, same sex, and same height can have large differences in the amount of bone. Those differences can vary by up to a factor of two. For example, one girl may have 10 grams of bone mineral in one lumbar vertebra while another physically similar girl of the same age may have 20 grams. What accounts for this variation? Many factors influence bone mass accumulation, and these factors together account for the differences in peak bone mass among individuals.
Even kids and teens who appear healthy might not reach their optimal peak bone mass. Blame their unhealthy lifestyles. As one parent expressed it, "Just when those hormones become supercharged we lose control over what our teenagers are going to do, eat, or say."
Most youths do not come close to meeting their daily recommended amounts of vitamin D or calcium. According to the latest figures, preteen and teen girls have the most serious deficiency, just at the time when more calcium is needed for growth. Only 15 percent of 9- to 13-year-old girls and 10 percent of 14- to 18-year-old girls met their daily requirements of calcium from diet alone. Meanwhile, 22 percent of 9- to 13-year-old boys and 42 percent of 14- to 18-year-old boys, met their daily recommended intake of calcium from foods. But still, the majority of boys consumed less than the recommended daily intake of 1,300 mg of calcium.
More time spent on the computer, playing video games, and watching television is usually at the expense of physical activity. Only about half of teenagers exercise on a regular basis. Inactivity is highest among girls, and Hispanic and African American teens.
Cigarette smoking continues to be adopted by teenagers. According to the Center for Disease Control (CDC), 20 percent of high school students smoke. The rate is about equal between boys and girls. Teen smokers often have other poor health habits, such as bad diets and lack of regular exercise.
Unhealthy lifestyle may also result in suboptimal peak bone mass. Proper nutrition with sufficient calcium, vitamin D, physical activity, and hormonal support is essential to maximize peak bone mass within genetically determined bounds. These are the absolute requirements for bone accumulation during growth as well as throughout adult life.
Misspent youth can make a big difference to future fracture risk. Optimizing bone health in childhood and teenage years results in stronger, denser bones in adulthood. More immediate benefit may result in fewer fractures as a preteen or teen.
THE THIRD DECADE: YOUR TWENTIES
A little more bone density may be added during your twenties. Gains of 5 to 12 percent in bone mineral density have been observed during the decade. This time period is referred to as consolidation.
The potential for bone gain in the third decade should not be ignored. For example, a student-initiated class project at the University of California, San Diego, looked at young college women, ages eighteen to twenty-five. We were astonished to find lower than average bone density by DXA scan in many of the students. From the information on their questionnaires, it was apparent that their diets were practically devoid of calcium. They had stopped drinking milk and were subsisting on low calorie, nutrient-poor diets. We provided a year's supply of calcium supplements to all of the young women. Those who had been calcium deficient showed increases in their bone density after one year.
This finding, as well as other reports, suggests that young women of college age might be able to reduce the risk of fractures in their later years by being attuned to their bone health and by making simple changes earlier in life.
THE THIRTIES AND FORTIES: WHAT GOES UP MUST COME DOWN
After reaching the maximum bone mass by age thirty, there is no nice plateau during middle age. Bone loss starts happening slowly with the process called remodeling, which is a little like climbing a mountain: You reach the summit, take some pictures to document your achievement, then slowly start to work your way down the other side.
Just as in growing your bone mass, the same supplies are essential to supporting bone remodeling, which is happening all the time. However, the bone remodeling process tends to result in a small net loss of bone.
If we go back to the 401(k) analogy, at retirement age you have no choice and you must make mandatory withdrawals. You try to be miserly by only making small withdrawals, and if you continue to provide all the essential supplies, it won't be too costly. But if you don't do your part in maintaining a healthy lifestyle, your savings may be raided: You might run out of money and end up bankrupt with a fracture.
For women, the natural course of events means that the supply of estrogen ends as you transition into menopause. Bone loss will accelerate before you even stop having menstrual periods. Bone remodeling speeds up and the bone formation side of the remodeling process can no longer keep up with the breaking down of bone. You end up with a net loss that can be rapid in the first four to five years of menopause, followed by the slower loss of bone that is more associated with aging.
Women who are heavier and have more body fat tend to lose less bone mass. The fat produces a weak estrogen, called estrone, which provides some extra support for the bone. But there is a downside: Obese women are still at risk for suffering fractures of the upper arm, ankle, and lower leg.
AGE-RELATED BONE LOSS
Adult bone mass is a reflection of peak bone mass, age at menopause for women, and rate of bone loss. Those who acquire a greater bone mass balance during the first thirty years of life will be at lower risk for fractures later in life. Although osteoporosis is primarily a disease of older adults, building a strong, dense skeleton during the growing years may be the best way to prevent osteoporosis.
If bone mass can be maximized during growth and development, you will begin adulthood with optimal bone mass and will be less likely to develop osteoporosis in later years. The more bone mass you "bank" in childhood and adolescence, the better you will withstand the inevitable bone loss that comes with aging and the better protected you will be from osteoporosis and bone fractures.
Now you should understand why osteoporosis is truly a childhood disease that manifests in later life. Increasing awareness and education about bone health in our children, grandchildren, and loved ones' lives is vital to prevention of fractures with aging. Improving modifiable factors of diet, physical activity, and calcium and vitamin D intake will result in maximizing bone growth. Achieving a high peak bone mass will lessen the impact of age-related bone loss and menopausal bone loss in women. A healthy lifestyle in childhood may have immediate beneficial effects by decreasing childhood fractures and by establishing healthy habits for one's lifetime.
The Bare Bones
Low birth weight is associated with osteoporosis as an adult.
Puberty starts the most important time for bone mass acquisition.
Bone mass approximately doubles between the onset of puberty and young adulthood.
Bone loss begins after achieving peak bone mass in the early thirties.
In women, bone loss accelerates at menopause with loss of estrogen.
Gradual and steady bone loss occurs with aging.
Excerpted from THE COMPLETE BOOK OF BONE HEALTH by DIANE L. SCHNEIDER Copyright © 2011 by Diane L. Schneider. Excerpted by permission of Prometheus Books. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.
Table of Contents
ContentsForeword by Sally Ride, PhD....................11
Introduction: To Your Bone-Healthy Life....................13
Drugs in Development....................255
Complementary and Alternative Medicine....................268
After a Major Fracture....................294