Vitamin d is the General name given to a group of liposoluble compounds
that are essential to maintain balance mineral in the body. It is also known as
calciferol and vitamin Dentiraquitica. The main forms are known as vitamin D2
(ergocalciferol: vegetable) and vitamin D3 (cholecalciferol: animal).
Since the cholecalciferol is synthesized in the skin through the action
of ultraviolet light in 7-dehidrocolesterol, a derivative of cholesterol that
is distributed widely in animal fat, vitamin D is not according to the
classical definition of vitamin.
In any event, given the number of factors influencing the synthesis,
such as latitude, season, air pollution, the area of exposed skin,
pigmentation, age, etc., vitamin d is recognized as an essential nutrient diet.
Main sources in nature
The richest natural sources of vitamin d are fish-liver oils and
saltwater fish such as sardines, herring, salmon and mackerel. Eggs, meat, milk
and butter also contain small quantities. The plants are weak sources and fruit
and dried fruit have no vitamin d. The amount of vitamin d in human milk is
insufficient to cover the needs for children.
Vitamin d is relatively stable in food; storage, processing and cooking
have little effect on their activities, although in fortified milk, might be
missed until about 40% of vitamin D added, as a result of exposure to light.
The cholestyramine (a resin used to stop the reabsorption of bile salts)
and mineral oil based laxatives inhibit the absorption of vitamin D from the
gut. The corticosteroid hormones, medicines anticonvulsivos and alcohol can
affect the absorption of calcium, reducing the response to vitamin d. animal
studies also suggest that medicines anticonvulsivos stimulate liver enzymes,
resulting in increased vitamin decomposition and excretion.
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Patients in treatment with thiazide diuretics or based antacids
containing magnesium should avoid taking high doses of vitamin d, due to
increased risk of hypercalcemia or hipermagnesemia respectively. Also found
that women taking oral contraceptives have blood levels of calcitriol slightly
Vitamin d is essential for homeostasis. Classically, it is necessary for
the absorption of calcium and phosphorus in the intestine, to its mobilization
from the bones and for the reabsorption kidneys. Through these three functions,
vitamin D plays an important role in ensuring the proper functioning of
muscles, nerves, blood clotting, cell growth and energy use. It is thought that
the depositing of minerals in the skeleton is the result of high concentrations
of calcium and phosphorus in the blood, thus only indirectly due only to the
action of vitamin d.
To run their biological functions, the calcitriol, like other hormones,
connects to target specific receptors in cells. Such receivers have been found
in a wide variety of fabrics. Has been proposed that vitamin d is also
important for the secretion of insulin and prolactin levels, and antibody
response to stress, synthesis of melanin and differentiation of skin cells and
Among the first symptoms of vitamin d deficiency are reduced serum
levels of calcium and phosphorus and increased alkaline phosphatase activity.
This may be accompanied by muscle weakness and tetany, as well as by increased
risks of infection. Children can show non-specific symptoms such as
restlessness, irritability, excessive sweating excessive and decreased appetite.
The marginal hipovitaminose D can contribute to brittle bones in the elderly.
The most widely recognized manifestations of vitamin d deficiency
rickets are (in children) and osteomalacia (in adults). Both are characterized
by mineral loss from bones, resulting in skeletal deformities, such as arched
legs in children. The ends of long bones in her arms as both legs are involved
and growth can be slowed. Rickets also results in inadequate mineralization of
enamel and dentin.
Have been identified some rare forms of rickets as occurring despite an
adequate intake of vitamin d. These are inherited forms in which the training
or use of calcitriol is committed. Osteoporosis, a disease of old age in which
bone loss occurs and not just demineralization, has also been associated with a
disturbance of the metabolism of vitamin d, but the results are controversial.
Groups at risk of disability
The risk of vitamin d deficiency is higher among children and the
elderly, especially those with low exposure to sunlight. In preterm infants and
infants with low birth weight, liver and kidney functions may be inappropriate
for an optimal vitamin d metabolism and the human milk is a poor source of
vitamin d. elderly food restrictions are an additional risk factor.
People with diseases that affect the liver, kidneys and thyroid gland or
absorption of fats, vegetarians, alcoholics and hypnotic therapy long-term
anticonvulsionantes, as well as people who are stuck at home, have a higher
risk of disability.
A specific risk group, which attracted attention in recent years, is the
population of India Western United Kingdom.
The recommended daily allowance (RDA)
It is difficult to establish a DDR for vitamin D, given the influence of
sun exposure. healthy people, with regular exposure to the Sun and under
appropriate conditions do not have needs for vitamin d in the diet. Given that
this is rarely the case in temperate zones, it is necessary a food supplement.
The Committee on food and nutrition research American National Council,
recommend a daily intake of 5 mg (200 IU) for adults, 7.5 mg (300 IU) for
infants under 6 months and 10 mg (400 IU) for children over 6 months pregnant
and breast-feeding mothers. A daily supplement of 5-7.5 mg (200-300 IU) is
recommended for infants fed with breast milk that does not have exposure to the
Elsewhere, the recommendation for adults ranges from 2.5 mg (100 IU)
11.5 mg (450 IU). The highest recommendation exists in France (20-30 mg per day
for children of black).
Monopreparacoes vitamin d and related compounds are available in
tablets, capsules, oily solutions and injections. Vitamin d also incorporates
in combinations with vitamin d, calcium and multivitamins.
In the treatment of rickets, a daily dose of 25 mg (1,000 UI)
cholecalciferol or ergocalciferol has with normal plasma concentrations result
of calcium and phosphorus within 10 days. Alternatively, doses of 75-100 mg
(3,000-4,000 IU) can produce faster results. However, the dosage should be
adjusted individually and calcium levels in plasma monitored regularly.
For the dependent rickets and vitamin d for hipocalcemia related
hipoparatiroidismo, may be required doses 1.25 mg (50,000 IU) or more. In
patients with osteoarthritis renal, may be preferable to use the calcitriol or
his analago alfacalcidol. With calcitriol, initial dosage is 0.25-2.0 mg (10-80
IU) per day.
The hypervitaminosis d is a potentially serious problem given that can
cause permanent damage kidneys, growth retardation, soft tissue calcification
and death. Lightweight poisoning symptoms are nausea, weakness, constipation
and irritability. In General a toxic dose for an adult is about 2.5 mg (100,000
IU) daily for 1-2 months; for children the toxic dose is between 0.5 mg (20,000
IU) and 1.0 mg (40,000 IU). However, certain individuals have a high
sensitivity to vitamin D and experience symptoms of toxicity only after 50 mg
(2,000 IU). The hypervitaminosis is not associated with a burning and the Sun.
Foods with Vitamin A