Bones are the framework for your body. Bone is living tissue
that changes constantly, with bits of old bone being removed and replaced by
new bone. You can think of bone as a bank account, where you make “deposits”
and “withdrawals” of bone tissue.
During childhood and adolescence, much more bone is deposited
than withdrawn, so the skeleton grows in both size and density. Up to 90
percent of peak bone mass is acquired by age 18 in girls and age 20 in boys,
which makes youth the best time to “invest” in your bone health.
Your bones are alive and constantly growing -- not static, like you see them drawn in books. Bones continually change throughout your life, with some bone cells dissolving and new bone cells growing back in a process called remodeling. With this lifelong turnover of bone cells, you replace most of your skeleton every 10 years.
But for people with osteoporosis -- a thinning of the bones -- bone loss outpaces the growth of new bone. Bones become porous, brittle, and prone to fracture. Look at an...
The amount of bone tissue in the skeleton, known as bone mass,
can keep growing until around age 30. At that point, bones have reached their
maximum strength and density, known as peak bone mass. In women, there tends to
be minimal change in total bone mass between age 30 and menopause. But in the
first few years after menopause, most women experience rapid bone loss, a
“withdrawal” from the bone bank account, which then slows but continues
throughout the postmenopausal years. This loss of bone mass can lead to
osteoporosis. Given the knowledge that high peak bone density reduces
osteoporosis risk later in life, it makes sense to pay more attention to those
factors that affect peak bone mass.
Factors Affecting Peak Bone Mass
Peak bone mass is influenced by a variety of genetic and
environmental factors. It has been suggested that genetic factors (those you
were born with and cannot change, like your gender and race) may account for up
to 75 percent of bone mass, while environmental factors (like your diet and
exercise habits) account for the remaining 25 percent.
Gender: Peak bone mass tends to be higher in
men than in women. Before puberty, boys and girls acquire bone mass at similar
rates. After puberty, however, men tend to acquire greater bone mass than
Race: For reasons still not known, African
American females tend to achieve higher peak bone mass than Caucasian females.
These differences in bone density are seen even during childhood and
Hormonal factors: The hormone estrogen has an
effect on peak bone mass. For example, women who had their first menstrual
cycle at an early age and those who use oral contraceptives - which contain
estrogen - often have high bone mineral density. In contrast, young women whose
menstrual periods stop due to extremely low body weight or excessive exercise,
for example, may lose significant amounts of bone density, which may not be
recovered even after their periods return.
Nutrition: Calcium is an essential nutrient
for bone health. Calcium deficiencies in young people can account for a 5 to 10
percent difference in peak bone mass and can increase the risk for hip fracture
later in life. Surveys indicate that teenage girls in the United States are
less likely than teenage boys to get enough calcium. In fact, less than 10
percent of girls ages 9 to 17 are actually getting the calcium they need each