Encyclopedia of Health and Medicine

200 Nutrition and Diet
ticipate in these chemical changes. In combination
with PARATHYROID HORMONE, calcitriol maintains a
steady level of calcium in the BLOOD circulation.
This balance allows the gastrointestinal tract to
absorb calcium from dietary sources and the bones
to accept calcium from the supply circulating in
the blood.
Rickets develops when a long-term deficiency
of vitamin D results in decreased dietary absorption
of calcium. To meet its extensive needs for
calcium, an important ion for numerous cellular
functions, including proper contraction of the
MUSCLE cells of the HEART, the body draws calcium
from the bones. The bones demineralize and
weaken. The long bones, notably those in the legs,
bow. Doctors generally use the term rickets to refer
to this disease process in children and the term
OSTEOMALACIA to refer to this disease process in
adults.
Symptoms and Diagnostic Path
The primary symptoms of rickets are bowed legs
and a protruding belly (the result of weakened
abdominal muscles). Deformities may develop at
the epiphyses, or growth plates, of the bones,
forming characteristic knobs and bumps. The diagnostic
path includes X-rays to assess the density
and mineralization of the bones and blood tests to
measure the levels of calcium, phosphorus, and
parathyroid hormone in the blood circulation. The
doctor will also take a thorough PERSONAL HEALTH
HISTORY including EATING HABITS.
Treatment Options and Outlook
Prompt vitamin D supplementation generally
reverses most circumstances of mild to moderate
rickets with little residual damage. Moderate to
severe rickets, which is fairly uncommon in the
United States, may result in consequential deformities
of the pelvis, rib joints, and knee and ankle
joints. Proper nutrition usually maintains adequate
vitamin D intake.
Risk Factors and Preventive Measures
Most people will synthesize (make) all the vitamin
D their bodies require with regular modest sun
exposure, about 20 minutes to the face and arms
four or five days a week. The farther from the
equator a person lives, the longer sun exposure is
necessary because the intensity of the sun’s ultraviolet
radiation diminishes. The ideal exposure is
that which is just less than what results in mild
SUNBURN. Doctors recommend multiple short exposures
(5 to 15 minutes several times a day) to
reduce the risk for sunburn. Applying sunscreen
before going in the sun, though a prudent and
recommended measure to prevent sun-related
skin damage when engaging outdoor activities,
prevents ultraviolet rays from penetrating the
skin. People who have dark skin require longer
periods of sun exposure.
Some health experts recommend that people
who live in regions where the hours of sunlight
drop below 12 hours a day (such as above 40
degrees latitude in the Northern Hemisphere,
which includes locations north of the US cities San
Francisco, Denver, St. Louis, Indianapolis,
Philadelphia, and New York City) take vitamin D
supplement. It is important to remain within the
recommended dosage guidelines, however,
because vitamin D is a fat-soluble vitamin that can
accumulate in the body to reach toxic levels.
The antiseizure medication phenytoin increases
the body’s METABOLISM of calcidiol, one of the
intermediary vitamin D forms. People who take
this medication may need therapeutic vitamin D
supplementation, particularly if they do not spend
much time outdoors. Young children who live in
inner city areas where smog is a problem have
increased risk for rickets even when they spend
time outdoors because the smog acts to filter the
sun’s ultraviolet rays.
See also ANEMIA; BERIBERI; FANCONI’S SYNDROME;
MALNUTRITION; NUTRITIONAL DEFICIENCY; NUTRITIONAL
NEEDS; PELLAGRA; SCURVY; VITAMINS AND HEALTH.