Vitamin D, a fat-soluble vitamin that is also considered a hormone, is responsible for the proper development of our bones and the good health of our skeleton. In recent years, however, several scientific studies have upgraded the important role of vitamin D in the overall health of the body, as it has been recorded that it helps improve immune function, control sugar and prevent other serious diseases such as various forms of cancer, multiple sclerosis , psychiatric diseases, hypertension, as well as other diseases.

The body absorbs vitamin D mainly through its creation in the skin under the influence of solar radiation (“vitamin of the sun”). Only a small amount can be absorbed from food. Foods that contain vitamin D are certain fatty fish (salmon, mackerel, tuna, cod, trout, sardines), cod liver oil, eggs (yolk), beef liver, shrimp, celery, and whole grains.

The composition of vitamin D in the skin depends on many factors, of which the main ones are listed below:

• Age: the body’s ability to produce vitamin D decreases with age
• The time of year: in winter its production is reduced, because the sunshine is less
• Latitude: latitude greater than 35° is associated with less vitamin D production, because the sun’s rays do not fall perpendicular to the earth.
• The color of the skin: its composition is less in dark skins, as melanin acts as a barrier to ultraviolet radiation.
• The use of sunscreen products, which prevent its composition.
• Other environmental factors such as air pollution and the ozone hole, which have a negative effect.

Vitamin D: Causes of deficiency

However, studies in southern countries have shown that vitamin D levels are very often lower than normal, and vitamin D deficiency is more common than in more northern countries. A recent study of the Greek population revealed that 57.7% have a vitamin D deficiency.

The most important reasons for this phenomenon are the following:

1. The latitude of Greece (34°-41°), which does not allow sufficient UV radiation, especially in the winter months.
2. Darker skin color
3. Possibly genetic predisposition
4. Residents of the northernmost countries of Europe consume larger amounts of fatty fish, rich in vitamin D. Conversely, in Greece, the main source of fat is olive oil, which contains a smaller amount of vitamin D.

Vitamin D: the benefits for the body

Its important contribution to the proper development and promotion of the health of our skeleton has been documented. Its severe deficiency leads to low levels of calcium and phosphorus in the blood, rickets in children (a condition that leads to bone deformation and growth retardation), osteomalacia and osteoporosis – fractures in adults.

Also, people with low vitamin D have an increased incidence of falls. The above has been documented with a number of well-designed studies. 

However, in recent years, a number of scientific studies have highlighted the important role of vitamin D, not only in the skeletal, but also in the overall health of the body, as it helps to reduce inflammation, to regulate and strengthen the immune system, to develop cells and to regulate the metabolism.

There are indications that its deficiency may be associated with an increased risk for several diseases, such as various malignancies (breast, uterus, ovary, bladder), autoimmune diseases (systemic lupus erythematosus, rheumatoid arthritis), inflammatory (Crohn’s disease, tuberculosis) and neurological diseases (Parkinson’s disease, schizophrenia, depression, multiple sclerosis), cardiovascular diseases (hypertension, arteriosclerosis, heart attack), endocrine disorders (diabetes, obesity). However, for the above there are mainly epidemiological data and further studies are needed to fully document the above data.

Addressing the deficiency

It seems that only intake with food is not enough, as very few natural foods contain a sufficient amount of the vitamin, while fortified foods usually cannot by themselves fully cover the daily needs. Thus, exposure to the sun is recommended, with the best time at noon (higher ratio of UVB/UVA radiation).

Exposure of 18% of the body (upper-lower limbs, face) to sunlight, for 10-15 minutes from 10 am to 2 pm, without sunscreen, three times a week is considered a sufficient period of time to provide the body with required amount of vitamin D.

Of course, there are concerns regarding exposure to solar radiation and causing skin cancer. Prolonged exposure to solar radiation should be avoided, especially in childhood. It seems, however, that chronic – not intense – exposure to sunlight is not a risk factor for the appearance of melanoma – on the contrary, it may be protective. In cases where the body’s needs are not met, vitamin D is administered orally.

There are many vitamin D products, in the form of pills or drops, in many dosages. We also find vitamin D in many nutritional supplements, along with other vitamins. There are even vitamin D formulations along with calcium.