Preserving bone density
After puberty, bone growth ends but bone density increases
until roughly age 30. Absorption and retention of calcium
decreases while calcium losses increase, leaving a requirement
that is estimated to be 1000 mg/day.
The drainage of calcium from bone occurs in all humans
at a steady pace, but women are clearly more at risk
for losses. Variability in calcium loss is best seen
in pregnancy when calcium is taken from the mother’s
stores for deposition in the fetus. Also, lactation
creates an ongoing need for further calcium supplementation
in women.
While most expectant mothers are able to replenish
their needs by taking prenatal vitamins, some teens
are not able to comprehend the necessity of increased
calcium intake and comply. Vitamin D is also supplemented
during this period in the prenatal pills, but even men
and non-pregnant women should maintain adequate intake
of this vitamin.
Exercise
A very important means of preserving bone density is
exercise. Adults have been made aware of the benefits
of exercise, especially in the elderly, for many reasons,
including the preservation of bone mineral content.
It is also well accepted that increased activity will
create forces on the bone that trigger increased bone
density - a natural response to protect highly used
bones by making them sturdier. Hence, it makes sense
that kids who get more exercise will also have stronger
bones.
Summary
To maximize the beneficial effects of increased bone
density in adults, we need to enhance the consumption,
storage, and preservation of calcium in kids and teens.
This starts with adequate and appropriate intake of
milk or substitute drinks, plenty of exercise, replacement
as needed for pregnancy and lactation, and the minimizing
of carbonated beverages.
Any dietary source of calcium will count toward the
child’s daily intake, but low-fat milk is clearly
the most efficient and readily available. Lactose-free
milk, soy and rice drinks have recently become more
easily obtainable and less expensive.
Parents should contact their child’s pediatrician
for specific details about calcium consumption or questions
regarding supplements in a chewable form.
By:
Julian Huang, MD
January 16, 2003
References:
- Food and Nutrition Board, Institute of Medicine.
Dietary Reference Intakes for Calcium, Phosphorus,
Magnesium, Vitamin D, and Fluoride. Washington,
DC. National Academy Press; 1997.
- National Institutes of Health, Consensus Development
Conference Statement, June 6-8, 1994.
USDA 1994 Continuing Survey of Food Intakes by Individuals
- Third National Health and Nutrition Examination
Survey – NHANES III.
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