Vitamin D - importance, source, deficiency, treatment

Vitamin D (calciferol)

There are several compounds with Vitamin D activity occurring in several forms; this group of related Chemicals is together known as vitamin D. 

So, vitamin D is a collective term for a group of compounds with antirachitic activity and includes ergocalciferol D2, cholecalciferol D3, and Dihydrotachysterol DHT2 and DHT3 together with their biologically active metabolites.

Vitamin D is now believed to be a hormone.

Vitamin D is considered to be a hormone rather than a vitamin because-

1. It is produced in the body from cholesterol, like other steroid hormones (estrogen, progesterone, etc).

2. It has a structure similar to the steroid hormone.

3. It's the mechanism of action that is similar to these hormones as well.

4. It regulates calcium metabolism and bone formation along with parathyroid hormone (PTH) and calcitonin (CT). 

Since both these are hormones and Vitamin D acts synergistically with this it is considered to be a hormone also.

Sources of Vitamin D: Most foods are poor sources of vitamin D. But vitamin D is not only obtained from foods but other sources are also available. Vitamin D sources can be divided into 3 main groups:-

(A) Food sources:- It was earlier believed that only animal sources contain Vitamin D, but it is now known that some plants also have vitamin D. Vitamin D is found in egg yolk, milk, butter, liver of all animals, fish, liver oil, etc. The content of vitamin D in animal foods depends on the exposure of animals to sunlight. The tomato plant is found to possess some amount of Vitamin D.

Vitamin D (IU/100 gm) content of foods:-

Cod liver oil - 10000 

Shrimp - 150 

Liver (lamb) - 120 

Cod - 85 

Butter - 35

Egg Yolk - 25

Cheese - 12

Corn oil - 9

Milk - 0.3-4.0

Spinach - 0.2

Cabbage - 0.2

(B) Cutaneous production: Human being produces vitamin D from sunlight with the help of 7-dehydro cholesterol present in the skin. If a person is a dark skin then vitamin D synthesis is less due to the presence of melanin pigment. Direct rays of the sun are needed for vitamin D production and so production is low in winter. Elder people synthesize less vitamin D than young. The use of sunscreen lotions, dark glass Windows, etc. can prevent vitamin D synthesis.

(C) Other sources: vitamin D is produced in the Placenta and other important issues of the body also chemical and these are not significant sources of this vitamin.

The daily requirement of vitamin D according to ages:-

Vitamin D requirements vary with age and other factors like the rate of production, the demand of the body, etc. In tropical countries, less vitamin D is needed through the diet since production is more.

Infant - 7.5 

Children - 1.0

Men (19-24 years) - 10

Men (25 & over) - 5

Women (19-24 years) - 10

Women (25 & over) - 5

Pregnancy - 10

Lactation - 10

Functions of vitamin D: 

Vitamin D is an important component of any diet and is being treated as a hormone rather than a vitamin. The most important functions of vitamin D are -

(1) Bone formation: Vitamin D helps deposition in the bones, probably of mineralized rather than amorphous (powder form) calcium phosphate by supplying Ca and P in proper concentration to the body matrix. It is believed that vitamin D stimulates the osteoblasts in the production of bones. These osteoblasts are bone forming cells. But the exact role of vitamin D in bone formation is not actively known. Like this teeth formation also takes place. 

(2) Hormonal role of vitamin D: vitamin D is considered a hormone since its functions are similar to that of some, hormone. Vitamin D acts at distant, target organs like the intestine and bones like hormones. It, together with parathyroid hormone and calcitonin, acts in maintaining several metabolic processes. Moreover, like hormones, vitamin D is synthesized in the body.

(3) Maintenance of calcium and phosphorus levels: The plasma Ca level is normally maintained at 9-11 mg/dl and P at 3.5- 5 mg/dl 100ml. This is done by increasing the intestinal calcium absorption, when necessary. If dietary calcium is inadequate vitamin D along with parathyroid hormone (PTH) releases Calcium from the bone. 

This produces loss of bone mass. 

Phosphate levels are also controlled by vitamin D. Phosphate is reabsorbed from the urinary tubule. If vitamin D levels are high then the Phosphorous level is low usually.

(4) Calcium metabolism: Vitamin D helps directly in the intestinal absorption of calcium and increases the synthesis of intestinal calcium-binding protein.

Vitamin D helps in the proper metabolism of calcium in the body, not only as a controller of calcium absorption but also as a regulator in those processes that calcium plays an important role.

Deficiency of Vitamin D: 

Deficiency of vitamin D can be manifested in the following manners:

(1) Ricket: This disease was first described by Glissob in 1650 in England where the disease was common especially among the children in the Smoky industrial areas. It is a Vitamin D and Calcium deficiency disease and this is due to the lack of deposition of calcium phosphate in the bones.

Clinical signs and symptoms of rickets: They are several clinical sign and symptoms commonly seen in rickets.

(a) Head: 

1. Somewhat enlarged, elongated, and flattened on the vertex (box head).

2. Prominent frontal bones.

3. Saif and cranial bones.

4. Excessive sweating on the head.

(b) Ribs:

1. Softening of the ribs.

2. Prominent costochondral junctions rickety Rosary.

3. Depression of the ribs along with the attachment of the diagram.

4. Reduction of the chest (funnel chest).

5. Deformities of the star. 

6. Pigeon breast.

(c) Epiphysis: characteristic swelling of the wrists and ankles due to expansion of epiphysis, ends of long bones.

(d) Deformities of long bones: 

1. Curvature at the junction of the lower and middle portion of the forearms and legs due to bone softening.  

2. The legs may be bent downwards due to pressure.

3. The child who can stand main develop knock-knee ( two Knees of legs come close to each other at the next move apart) or Bow-legs ( bones of legs become soft, the long bone is moved apart leading to a bone formation).

(e) spine: 

1. Kyphosis due to the lacs muscles 

2. Scoliosis

(f) Muscles: There are generalized hypotonia and muscle weakness known as rickety or muscle degeneration.

(g) Dentition: Dentition is delayed and the dental enamel is affected.

Prevention and treatment - Rickets is not a fatal disease but if untreated then the rachitic child may have an increased risk of infection and other problems. The amount of vitamin D required to prevent rickets in infants and children will depend upon their diet and exposure to sunlight. 

Vitamin D enriched milk and Milk products should be given to the child and 1 teaspoon of cod liver oil, which provides 10 mg of vitamin D, is adequate to protect against Rickets.

Usually, children of the Tropical countries have enough sunlight and usually do not require special Vitamin D supplementation.

Vitamin D and Calcium deficiency can be treated by supplying an adequate amount of these components in the diet.

(2) Osteomalacia: It is the adult counterpart of rickets. Osteomalacia refers to bone softening.

Prevalence: Osteomalacia is commonly seen in females among adults. Mainly those women who follow the 'purdah' system or the 'burkha system' or who are confined in their homes have these diseases. Such women are of childbearing age and consume a serial-based diet poor in Vitamin D and Calcium. The first pregnancy is the most common period of occurrence of osteomalacia.

Pathology: The biochemical changes in the blood are essentially the same as those in rickets. The bones become disqualified and these tissues are replaced by soft osteoid tissues.

Cause: 

1. Lack of dietary intake of vitamin D or sunlight. 

2. Malabsorption of vitamin D (due to intestinal problems). 

3. Secretion of milk during lactation. 

4. Excessive demand as in pregnancy. 

5. Impaired 25-hydroxylation in the liver, due to liver disease. 

6. Impaired hydroxylation in the first position, which occurs in the Kidney, due to kidney diseases. 

7. Complete shielding, by the purdah, from exposure to sunlight. 

8. Hyperpigmentation in dark-skinned people leads to less production of Vitamin D. 

9. It is seen in old people who have improper food intake.

Clinical symptoms: 

1. Skeletal pain. 

2. Bony tenderness. 

3. Fractures. 

4. Low density of bone Matrix. 

5. Deformed bones. 

6. Pseudo Fractures (looser zone). 

7. Deformities of ribs, vertebra, pelvis legs, etc. 

8. Muscular weakness.

Treatment: A daily oral dose of 25-125 mg of vitamin D cures osteomalacia. 10 mg of vitamin D regularly can prevent osteomalacia. Sometimes a single massive dose of 50000 IU you can be given intramuscularly which can last for six months after 6 months the patient should consume daily 400 IU of Vitamin D.

The best source of vitamin D and Calcium is milk and these should be consumed in proper amounts to prevent osteomalacia.

(3) Osteoporosis: Osteoporosis is the disease of bone most frequently encountered in old people. It may be a localized disease.

Causes: The cause of osteoporosis can be described as - 

(a) Hormonal deficiency: The frequency with which osteoporosis 

develops in women after Menopause and the fact that it is much more common in women than in men has led to the view that a failure of sex hormone secretion may be one of the factors concerned with the production of this type of osteoporosis. A similar condition in men, often described as senile osteoporosis is thought to be related to diminished androgen formation.

(b) Ca & vitamin D deficiency: are hi facial content of calcium and the low calcium absorption has been reported in osteoporosis by some workers. This suggests that a failure in calcium absorption is due to low intake and less absorption of vitamin D.

(c) Immobilization of insufficient physical activity: Immobilization of a limb for any reason lead rapidly due to the demineralization of the bones. In support of this view is the finding that the incidence of osteoporosis in old people is high in western countries and low in people in underdeveloped countries who have to carry out basic physical activities for survival.

(d) This Occurs due to the absorption of the bones.

Clinical symptoms of osteoporosis: 

1. Skeletal pain is associated with the fracture. 

2. Fractures are very common, which heel normally. 

3. Loss of density of bones is irregular and often most marked in the 

spine. 

4. Bone reduced in quantity but fully mineralized.

Treatment of Osteoporosis: If treatment with sex hormones is advised for women because of pain and frequency of fractures sitosterol is recommended in a dose of 1-3 mg a day for a period of four to five weeks. For senile osteoporosis in males, methyltestosterone may be given continuously in a dose of 25 to 50 milligram a day sublingually for two weeks. It is also essential to make sure the dietary intake of calcium and vitamin D is satisfactory.