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The most important dietary sources of lipophilic vitamins
Šafránková, Simona ; Hejtmánková, Alena (advisor) ; Táborský, Jan (referee)
Basic piece of knowledge about nutrition and its need should be integral to every mans general knowledge. One of the vital nutritions ensuring a full-functioning organism are vitamins. Vitamins are essential ingredients, which play an important role in the human body and also in the processes of absorption and the exchange of substances between the external environment and living organism. They were discovered recently during the 20th century. The researches on their effects on the human body are still ongoing.
The vitamins are divided into two basic groups, water soluble vitamins, the so called hydrophilic (vitamins B and C), and fat soluble vitamins, the so called lipophilic (vitamins A, D, E and K).
The vitamin A is important to ensure good vision and recognizing colors. It support the quality and growth of bones, affects the egg and sperm and is needed for proper fetal development.
Vitamin A is found in foods of animal origin, such as dairy products, milk, meat and liver. In the food of plant origin, the vitamin A is replaced with many provitamins, of which most important is the beta carotene. A very rich source of these provitamins are leafy greens such as spinach or cabbage.
The recommended daily intake of vitamin A is 800 microgram, according to the standards of Czech republic. This need depends on the gender and age of each individual. The lack of vitamins A causes photophobia and impaired vision. The excess of vitamin A may be toxic for the organism. The interesting fact is that the beta carotene is not considered to be toxic.
Vitamin A is one of the labile vitamins. It is sensitive to heat, light and oxygen. At a gentle meal preparation and usual diet, the losses are around 20 %.
The vitamin D is consisted of group of several biologically active substances, of which the most important are vitamin D2, ergokalciferol, to be found in foods of plant origin, and vitamin D3, cholekalciferol, to be found in foods of animal origin.
In the human body, vitamin D acts as a hormone, it is formed at one point of the organism, but affects a different part of the body. The vitamin D ensures the intake and absorption of calcium and phosphorus and maintain their balance. It supports the immune system and may help in the psoriasis treatment.
The recommended daily intake of vitamin D is about 2,5 to 10 microgram. Pregnant and lactating women have a greater need for it, as well as infants and children. The lack of vitamin D disturbs the homeostasis of calcium and phosphate metabolism. The excess of vitamin D causes hypercalcaemia.
The most important foods source of vitamin D are liver, oil from fish liver, oil sea fish, fortified margarine and milk.
Vitamin D is sensitive to oxygen and light, its activity is not significantly affected by food storage or preparation.
Vitamin E is a major antioxidant. It is important to maintain the healthy cell wall and skin, muscles, nerves, erythrocytes, heart, and it is also responsible for the proper function of blood circulation.
The recommended daily intake of vitamin E is 8 to 20 mg. Its need is increased during exposure to sunlight and harmful influences, during increased physical exertion and when receiving large amounts of unsaturated fatty acids. The lack of vitamin E almost does not occur in healthy people, since it is present in nearly all basic kind of foods. The hypervitaminosis of vitamin E occurs only rarely, because there is no risk of overdose when receiving a normal diet.
The most important foods source of vitamin E are vegetal oils (such as sunflower and rapeseed), nuts, corn, pea, corn products, dark green leaf vegetables, eggs, liver and viscera.
Vitamin E is considered the most stable lipophilic vitamin. There is only a minimal loss of tocopherol during food processing, these losses are approximately 10 %.
The vitamin K supports blood clotting in the human body and, along with the vitamin D, is involved in the constant bone development and remodeling.
Both foods of plant and animal origin are sources of vitamin K, such as meat, liver, milk, vegetables and fruit. The recommended daily intake of vitamin K is around 0,01 to 0,14 mg. The infants and children up to three years have lower need of vitamin K intake. The most common cause of vitamin K hypovitaminosis is disruption of intestinal microflora caused by various drugs, e.g. antibiotics. Too high doses of vitamin K can accumulate in the body and lead to the breakdown of erythrocytes, damage the liver and cause jaundice in children.
There is not much information known about the stability of vitamin K yet. It has been found that vitamin K decomposes rapidly in the light, however its losses during food processing are minimal.
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