FRACTURED HEALTH: SEX DIFFERENCES IN BONE HEALTH

Jennifer Wider, MD
SWHR, Contributing Writer
October 11, 2012

By the age of 18, roughly 85 to 90 percent of bone mass is acquired, also known as peak bone mass, and bone formation is almost complete. In order to maximize bone health, it is critical for girls to get enough calcium and vitamin D in their diets at an early age.

Bones make up the support structure of the body. For women, bone health begins at an early age due to peak bone mass. According to information from the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), bone tissue in the skeleton can continue growing until the age of 30. Women experience marginal changes in total bone mass between age 30 and menopause. In the first few years after menopause, however, many women experience rapid bone loss which can place them at risk for osteoporosis and bone fractures.

“Women are more at risk for osteoporosis based on sex,” said Kimberly Templeton, MD, professor of Orthopaedic Surgery and Health Policy and Management at the University of Kansas Medical Center in Kansas City. “Although if you looked at bone under the microscope, the bone in young women and men looks the same, women lose bone earlier than men. Estrogen keeps osteoclasts (cells that remove bone) under control.”

Hormonal changes also increase bone risk for older women. “With menopause (either naturally or medically induced), that control is lost and more bone is lost than is made,” said Dr. Templeton. “Men tend to lose bone later, as a result of loss of testosterone (that supports new bone formation) and aging. Men will lose bone earlier only if other health conditions intervene - the most common being loss of testosterone, continued use of systemic corticosteroids, and alcoholism.” Women are also more likely to experience a bone break or fracture, explains Dr. Templeton because “their bones are smaller. Bone strength depends on the size, quality, and quantity of bone.”

After the body's skeleton forms and grows to its adult size, it completely regenerates itself about every 10 years, through a process called remodeling. Remodeling removes old pieces of bone and replaces them with new, fresh bone. This keeps the bone and its cells healthy and strong, and allows the bones to supply calcium to the body.

Keeping the skeleton in good repair requires a balance between the removal and replacement of bone tissue. In young healthy adults, the amount of bone removed and replaced is about the same. This is called balanced bone remodeling and is controlled by your bone metabolism. As we age, the remodeling process may shift out of balance, resulting in loss of bone structure and strength, and lead to bone disease, such as osteoporosis.

According to data from NIAMS, a range of genetic and environmental factors seem to influence peak bone mass, including:
 •Gender: Before puberty, boys and girls acquire bone mass at similar rates. After puberty, men tend to acquire greater bone mass than women.
 •Race: African American women tend to have higher peak bone mass than Caucasian women, even during childhood and adolescence, for reasons not yet fully understood.
•Hormones: Estrogen plays an important role in peak bone mass. Studies show girls who menstruate at an early age often have higher bone mineral density than girls who begin menstruating later.
 •Lifestyle: Smoking has been linked to lower bone mineral density. Chronic smoking has a negative influence on peak bone mass, placing older smokers at risk for bone loss and fracture. A sedentary lifestyle is another risk factor for poor bone health. Girls and boys who exercise regularly often have a higher peak bone mass than those who do not.
 •Diet: Calcium is an important nutrient for bone health and it is essential women receive enough calcium in their diet to prevent bone loss.

Brittle bones and fractures are not an inevitable part of aging. There are ways to safeguard your bone health. Women ages 19-50 need 1,000 mg of calcium and 600 IU of vitamin D3 (cholecalciferol) every day. After 50, women need 1,200 mg of calcium and 600 IU of vitamin D3. Performing weight-bearing exercises on a regular basis is also an important part of maintaining good bone health. Jogging, gardening, and working out with weights are all great ways to keep your bones healthy. If osteoporosis or other bone diseases run in your family, speak to your health care provider about ways to screen for and prevent these conditions.

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For more information on the Society for Women’s Health Research please contact Rachel Griffith at  202-496-5001  or Rachel@swhr.org.

Jennifer Wider, M.D.,is a medical advisor for the Society for Women’s Health Research (SWHR), a national non-profit organization based in Washington D.C., widely recognized as the thought leader in research on sex differences and dedicated to improving women’s health through advocacy, education, and research.

Dr. Wider is a graduate of Princeton University and received her medical degree in 1999 from the Mount Sinai School of Medicine in New York City. She is frequently published in newspapers, magazines, and websites and has been a guest on the Today Show, CBS News, Fox News, Good Day New York, and a variety of cable channels. Dr. Wider hosts “Paging Dr. Wider,” a weekly segment on Sirius satellite radio for the Cosmopolitan magazine channel.

Dr. Wider is a past managing editor of the health channel at iVillage.com. She writes a monthly news service article for SWHR and is the author of the consumer health booklet “Just the Facts: What Women Need to Know about Sex Differences in Health” and the book “The Doctor’s Complete College Girls’ Health Guide: From Sex to Drugs to the Freshman Fifteen.”