The utility of vitamins for vital activity was researched from the beginning of the 20th century. Scientists discovered one vitamin after another. It was noticed that different groups of vitamins were responsible for different vital processes in our organisms. Normal vital activity is not possible without a certain portions of vitamins that we usually receive with the variety of foods and products.
Vitamins are divided into two main parts including fat-solvent and water-solvent vitamins. Water-solvent vitamins are not collected in the body and are easily removed by means of natural liquid. That is why it is obligatory for a human being to receive them with daily diet. Fat-solvent vitamins are not removed from the organism very quickly, they are collected, and overdose as well as deficiency may lead to serious consequences. Among them there are vitamins of the group A, O, E, K and D.
Fat-solvent vitamin D is received from the ultra-violet light. Especially in the sunny seasons from May to September when we expose our skin to the sunlight and our organism obtains the required quantity of this vitamin and is kept in the fatty layer of our skin, and later is penetrated in the body. But the sources can also include vitamin D foods.
Foods rich in vitamin D are the following: fat oils, fatty fish, such as salmon, mackerel, sardines, eel, etc., also vitamin D foods are beef liver and milk. Vitamin D milk is a special fortified milk that is produced especially for those who have vitamin D deficiency. But everyone should not forget that overdose is no less harmful than deficiency. For adult people it is normal for sunbathing every day in order to maintain the balance of the vitamin D in the body. Physicians do not advice to take vitamin D supplements if it is not required. It would be enough to walk in the sun and eat vitamin D foods. Toxic effects of the vitamin D overdose are not very pleasant: excessive thirst, eye inflammation, emesis, skin itch, diarrhea, etc.
The liver of the adult human is able to collect the necessary amount of the vitamin D required for one year. Everyday diet should not exceed 1 microgram of the vitamin. But for children, new-born infants and some older people vitamin D is prescribed additionally. Older people, who do not have the opportunity to walk everyday in the sun, can feel the vitamin D deficiency that may lead to serious problems with bones. Children need vitamin D supplements because their bones just grow, and the properties of the vitamin D foods and supplements help them to grow correctly to avoid rackets.
There are other categories of adult people who are recommended to eat more vitamin D foods or take extra supplements: night shift workers, monks, etc.
Vitamin D plays an important role in the utilization of calcium and phosphorus that are required for bones and teeth to be stronger. It maintains the required calcium and phosphorus level in the blood. It is strongly recommended for preventing rickets, osteomalacia, high blood pressure, chronic fatigue, autoimmune disease, osteoporosis and many other diseases.