General Description
The term vitamin D is used to describe two substances from two different
sources. Vitamin D-3, cholecalciferol, is formed from cholesterol
and is synthesized in the body during exposure to ultraviolet light
(e.g. sunlight). The other substance is vitamin D-2, ergocalciferol,
which is found in plants and is used to fortify foods such as margarine,
cereals, and milk. Both substances perform the same function in
the body.
Health applications
Functions and uses
Vitamin D (cholecalciferol and ergocalciferol) promotes intestinal
absorption of calcium and phosphate into the blood stream. It also
frees calcium from bones for use in other parts of the body. It
is essential for normal bone growth and development. It also works
in the kidneys to prevent calcium and phosphate loss through urine.
Both forms of vitamin D are converted by the body into an active
form called calcitriol. The liver and kidneys are involved in this
process. For this reason, kidney failure often results in calcium
deficiency symptoms.
Rickets
Rickets is a disease that causes bone deformity and stunted growth
in children. It can be hereditary and often occurs in people who
are vitamin D deficient. Studies show that doses of the activated
form of vitamin D-3, calcitriol, effectively treats most kinds
of rickets.1-6 Increased exposure to the sun
also helps and is sometimes a recommended treatment.5
At times, especially during the winter months, people
do not incur enough ultraviolet stimulation to satisfy their daily
requirements of vitamin D. In such instances, fortified foods
can help prevent rickets and osteomalacia.
Psoriasis
Psoriasis is a skin disease in which areas of skin on the body
become inflamed, turn red, and peel. The disease affects 0.2 -
2% of the population, and usually occurs between the ages of 20
and 60. Genetics seems to play a role in the disorder, as two
psoriatic parents have about a 75% chance of passing it on to
their children. There is no cure for psoriasis, but studies show
that Vitamin D can help to alleviate some symptoms.7-11
Often, treatments are in the form of topical creams that are directly
applied to the affected areas.
Crohn's disease
Crohn's disease is a chronic inflammatory bowel disease that causes
scarring in the intestinal walls, which can subsequently interfere
with the digestive process. Often people with this disease suffer
from malabsorption of vitamin D. This in turn may lead to bone
demineralization and osteomalacia. Studies show that vitamin D
supplementation may help alleviate the possibility of such complications.12-14
Dosage and toxicity
Vitamin D is available in many multivitamin formulas. The RDI
is 400 IU of vitamin D daily. This recommendation does not take
into account the fact that people may be producing sufficient
amounts of the vitamin due to exposure to the sun. It can be toxic
if taken in doses larger than 400 IU. Symptoms of toxicity are
headache, nausea, vomiting, metal taste in the mouth, fatigue,
and muscle and bone pains. In addition, excess vitamin D can lead
to an accumulation of calcium in vital organs, such as the liver
and kidneys, with potentially dangerous consequences.
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