Whole Food Nutrition
Vitamin D
Vitamin D plays an important role in the maintenance of an
intact and strong skeleton. Its primary task seems today to be
to regulate the amount of calcium and phosphorus in the blood by
ensuring correct intake from intestines and secretion. However,
other related tasks are still under investigation
Several studies show that vitamin D also regulates the growth of
skin cells. Psoriasis gives shell-like skin as a result of
uncontrolled cell growth. A synthetic vitamin D analogue called
calcipotriene is used in the treatment of this disease.
The human body produces its own vitamin D in the skin - this is
done by activating some chemicals in the body. This process is
dependent on ultraviolet radiation from sunlight. However,
vitamin D should not be excluded from the diet, especially for
people who do not receive sufficient exposure to UVB sunlight.
Vitamin D is best known for its role in the development and
maintenance of healthy teeth, bones, and cartilage in children
and adults. Vitamin D helps the body keep bones and teeth strong
by increasing absorption of calcium and phosphorus from the
small intestine.
Vitamin D is one of those vitamins for which a deficiency can
cause severe effects. Children that do not get enough vitamin D
in their diets are at increased risk of developing rickets, a
disease that causes malformations of bones and teeth in
children. Adults with low levels of vitamin D are more likely to
develop osteomalacia (similar to rickets) and to suffer from
osteoporosis, a bone-weakening disease. Vitamin D also regulates
the nervous system, aiding in the treatment of insomnia. A glass
of warm milk before bed may indeed help you sleep soundly!
Vitamin D deficiency has also been linked to the development of
other illnesses, including type I diabetes, muscle and bone
pain, and cancer.
There are two forms of Vitamin D: ergocalciferol, which is found
in such foods as fortified milk, herring, mackerel, tuna,
salmon, sardines, eggs, fortified cereals and baked goods; and
cholecalciferol, which is manufactured when the body is exposed
to sun.
Vitamin D is fat-soluble. This means that excess amounts of it
are stored in the body tissues. Long-term high doses may be
deposited in the soft tissues, irreversibly damage the kidneys
and cardiovascular system. Like other fat-soluble vitamins,
vitamin D can be toxic. Symptoms of too much vitamin D include
nausea, weakness, constipation, irregular heartbeat, weight
loss, seizures, and irritability.
Sunlight is the best source of vitamin D, because sunlight
exposure does not cause vitamin D toxicity, and 10 minutes of
sun on your hands and face provides enough vitamin D to reach
the daily value. However, getting the necessary amount of
vitamin D from the sun is not as simple as it sounds. For one
thing, people in northern hemisphere may have difficulty getting
vitamin D from sun in the winter due to infrequent exposure to
direct sunlight (light coming through a glass window of a car or
building doesn’t count, because it filters out vitamin D). Also,
the recent explosion in the number of skin cancer cases has
caused the public to use more and stronger sunscreen, which
inhibits the body’s ability to manufacture its own vitamin D
from sunlight. In his book, The UV Advantage, Dr. Michael Holick,
one of the world's most respected authorities on vitamin D,
discusses the health benefits of natural sunlight. However, if
you have a history of skin cancer, or are simply trying to avoid
anything that could cause more wrinkles, it is probably best to
try to get the vitamin D needed from your diet instead rather
than the sun.
The major source of vitamin D in our diet is fortified milk, but
it would take one quart of fortified milk to provide the Daily
Value. Because there are relatively few foods that contain
vitamin D, you may wish to rely on a vitamin supplement to meet
your daily needs.
The Recommended Dietary Allowance (RDA) of vitamin D is 800
International Units (IU) for children 18 and under, 600 IU for
adults 19-22, and 400 IU for anyone over 23 years. Healthy
infants are born with enough vitamin D to last them three
months.
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