Vitamin D

What is Vitamin D?

What is Vitamin D and what roles does it play in the body? This vitamin is involved in maintaining normal blood levels of phosphorus and calcium. It is also known to help in the body’s calcium absorption, aiding in the formation and keeping strong bones.

Recent studies have shown that vitamin D provides protection from high blood pressure or hypertension, osteoporosis, cancer, and other numerous autoimmune diseases.

Vitamin D is basically a group of fat-soluble secosteroids that are mostly found in various dietary sources such as eggs, milk, fish and cod liver oil.

The sun is a significant contributor to the daily production of vitamin D, wherein a 10-minute exposure to the sun is already enough to stimulate the production of vitamin D in the body. There are two major forms of essential vitamin D in humans: these are are cholecalciferol, vitamin D3 that is synthesized by the human skin when exposed to ultraviolet-B (UVB) rays from sunlight; and ergocalciferol, vitamin D2 that can only be synthesized by plants.

Ergosterol is synthesized by plants and can be converted to vitamin D2 with the aid of ultraviolet light.

Foods are fortified with either vitamin D2, D3 or both. Adequate intake of vitamin D is vital to one’s health.

Vitamin D Function

By itself, vitamin D is biological inactive, wherein proper processes should be conducted to metabolize it to its biologically active form. Whether synthesized in the epidermis of the skin, or consumed through diet, vitamin D will enter the circulation and will be transported to the liver. Some of the significant functions of vitamin D involve the following:

  1. Calcium balance. The maintenance of the serum calcium levels within a contracted range is essential for the nervous system’s normal functioning, as well as for the maintenance of bone density and bone growth. Vitamin D is vital for the body’s efficient utilization of calcium and when the calcium level drops, the parathyroid glands such changes and will secrete parathyroid hormone (PTH).
  2. Immunity. In the form of 1,25-dihydroxyvitamin D, vitamin D is a potent modulator of the immune system. There are various scientific evidences that shows the variety of effects of 1,25-dihydroxyvitamin D on the function of the immune system, which can inhibit the development of autoimmunity and enhance innate immunity as well.
  3. Cell differentiation. It is known that rapidly dividing cells are proliferating. The specialization of cells for certain functions results in cell differentiation, which leads to a decrease in proliferation. Although this process is vital for wound healing and growth, uncontrolled proliferation of cells together with mutations, can cause diseases such as cancer. The 1,25-dihydroxyvitamin D, which is an active form of vitamin D, prevents proliferation while stimulating the differentiation of cells.

Vitamin D Deficiency

Lack or deficiency of vitamin D can result to certain diseases and health disorders such as:

  1. Rickets. Severe vitamin D deficiency for infants and children results in the failure of the bone to mineralize. Rickets can severely affect rapidly growing bones; although there is a continuous enlargement of the bone’s growth plates, the arms and legs (weight-bearing limbs) become bowed due to the absence of adequate mineralization. Rickets can result to the delayed closure of the skull’s soft spots, known as fontanels, in infants and the rib cage becomes deformed because of the diaphragm’s pulling action.
  2. Osteomalacia. Even though the bones of adults are no longer growing, they are still in a so-called “remodeling” state of turnover. Severe deficiency of vitamin D in adults allows preservation of the collagenous bone matrix yet the bone mineral is progressively lost, which in turn causes osteomalacia or soft bones and bone pain. This is of course also linked to the conditions of osteopenia and osteoporosis.
  3. Muscle pain and weakness. Deficiency of vitamin to adults and children can cause muscle pain and weakness, according to the study of Arab and Danish Moslem women living in Denmark.

Food Sources of Vitamin D

As discussed above the body is able to create vitamin D once the skin is exposed directly to the sun, which is why it is mostly termed as the ‘sunshine vitamin‘. The majority of people all across the globe, meet their body’s vitamin D needs this way.

However it is often the case that some people do not get an adequate supply of sunlight due to bad weather, and bad light at high latitudes. There are a few foods that are known to contain vitamin D naturally. Fortunately several foods nowadays are fortified with vitamin D. This basically means that vitamin D has been artificially added to the food.

Cheese Vitamin D

Cheese, such as this blue Stilton is a good source of Vitamin D

Some of the major food sources of vitamin D are as follows:  Cream, butter, cheese, oysters, dairy products, fortified milk, fatty fish, fortified breakfast cereals, soy milk, and margarine are food sources of vitamin D.

References And Further Reading

Stilton Cheese Photograph by Lisa BrewsterHarvard School of Public Health; Wikipedia; Medline Plus; Linus Pauling Institute; Mayoclinic.