Calcium-Poor
Diets Limit Girls' Bone Strength Potential
Mother
Nature's best efforts to protect growing bones come
up short when girls' diets contain too little calcium,
according to a recent CNRC study.
 "We know a substantial proportion of adolescent
girls have very calcium-poor diets. Yet, little was
known about how well their bodies can adapt to minimize
the effect of this nutritional challenge," said
Dr. Steven Abrams, a Baylor professor of pediatrics
who studies calcium metabolism at the CNRC.
Bone
development peaks during puberty, which is why calcium
recommendations for children over the age of 8 jumps
to 1300 milligrams per day, or the equivalent of about
4 cups of milk, Abrams said. However, dietary surveys
suggest that one in five adolescents consumes one-fourth
that amount -- or less.
For the study, thirty-six 9- to 13-year old Caucasian
and African-American girls followed either a very-low-calcium
or a high-calcium dietary regime for three weeks. The
very-low-calcium regime provided one-third the amount
of calcium recommended for this age group each day;
the high-calcium regime provided the recommended amount.
Changes in calcium retention, which is the amount of
calcium the girls absorbed from the diets minus natural
body loses, was monitored using non-radioactive tracers.
Following a six-week break, the girls switched dietary
regimes and repeated the study.
"Since factors such as ethnicity, age, and
maturity influence calcium metabolism, the study required
that each girl complete both dietary regimes," Abrams
said. Once the study was complete, this enabled the
researchers to use each individual's high-calcium study
results as a baseline, or control, to accurately determine
the effect of the very-low-calcium regime on calcium
retention.
"Although the girls responded to the low-calcium
regime by boosting the percent of calcium they absorbed
by nearly fifty percent and cutting body losses in
half, their calcium retention was still less than half
that achieved on the high-calcium regime," Abrams
said.
Because calcium retention determines how much calcium
the body can deposit into bones during puberty, the
50 percent shortfall in calcium retention with the
very-low-calcium regime is troubling.
According to Abrams, he study results strongly suggest
that following very-low-calcium diets over a prolonged
period of time can put adolescent girls' long-term
skeletal health in jeopardy and increase their risk
of debilitating bone diseases like osteoporosis.
"Teens and parents need to understand that
there are limits to the body's ability to adapt to
a diet that is short on calcium or other key nutrient," Abrams
said.
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