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Described vitamins: Vitamin A | Vitamin C | Vitamin D | Vitamin E | Vitamin K


Vitamin A

Description vitamin A
Vitamin A is a group of fat-soluble substances that are found in animal products. Vitamin A also includes carotenoids, which are produced by plants. These are transformed to retinal. Fruits and vegetables for example contain beta-carotene, which is converted to vitamin A in the human body.

Functions of vitamin A
Vitamin A is essential for the development of bones, skin and eyesight. It strengthens the immune system, creating resistance to infection and disease.

Vitamin A in food
Food sources that contain retinol and retinal are animal products, including: liver, kidney, oily fish, dairy, eggs and margarine. Carotenoids are found in oranges, yellow, orange and dark green vegetables and fruits (for example carrots, broccoli, spinach and watercress).

Vitamin A as a supplement
Vitamin A is recommended therapeutically for patients experiencing skin conditions (eczema, acne, psoriasis) and night blindness. Vitamin A plays an important role inthe prevention of several types of cancer.

Vitamin A is not recommended for pregnant women. Excess vitamin A may cause birth defects. However, an adequate supply of vitamin A is still required because of its essential role in embryonic development.

Vitamin C

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Description Vitamin C
Vitamin C is also referred to as ascorbic acid. It is essential for normal body functioning. Humans must obtain vitamin C trough their diet. Other mammals have the opportunity to produce their own vitamin C supply.

Functions of Vitamin C
Vitamin C plays a role in the fat transport system of cells and cholesterol metabolism (prevention of gallstones). Vitamin C is a powerful antioxidant that assists the body in contesting viral infection, bacterial infections and toxicity. It protects carbohydrates, fats, proteins and nucleic acids (DNA and RNA) from damage induced by free radicals and other reactive species. Vitamin C produces skin products to enhance skin vitality and it plays a role in wound healing. Vitamin C deficiency causes bruising, bleeding, skin and hair loss.

Vitamin C in food
Vitamin C is present in fresh fruit and vegetables and in fruit juice juices, (kiwi, Brussels sprouts, peppers).

Vitamin C as a supplement
Vitamin C is recommended to those that have skin and hair loss problems, slow-healing wound, infections and colds, congestive heart failure, high cholesterol, bleeding, high blood pressure, atherosclerosis, angina or scurvy. People that smoke, drink or use contraceptive pills may benefits from additional vitamin C. Elderly people and people taking antibiotics may get prescriptions as well. Taking adequate amounts of vitamin C each day by eating sufficient amounts of fruit and vegetables may decrease the risk of cancer.

Cooking may destroy vitamin C pools in fruits and vegetables.


Vitamin D

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Vitamin D is a fat-soluble vitamin that exists in various forms. The form mainly used by humans is cholecalciferol (vitamin D3). This vitamin is formed when cholesterol in the skin is exposed to ultraviolet sunlight. Vitamin D only has physiological effects when it is first modified by the body.

Vitamin D is essential for development bone growth and density and for functioning of the nervous system. Vitamin D is also essential for heart functioning. It also plays a role in calcium metabolism.

Vitamin D in food
Vitamin D is usually obtained from sunlight, but there are some food stuffs that contain the vitamin. Examples include dairy products, fish oil, liver and egg yolk. Margarines may be fortified with vitamin D.

Vitamin D as a supplement
Vitamin D medication is recommended to people on law fat diets, vegans and people that are usually not exposed to bright sunlight or have moved to regions with a colder climate.

People taking heart medication may not take vitamin D.


Vitamin E

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Description Vitamin E
Vitamine E is a name for eight antioxidants, of which the only one active in the human body is referred to as a-tocopherol.

Functions of Vitamin E
Vitamin E is an antioxidant which intercepts free radicals and therefore prevents lipid destruction chain reactions. It maintains the integrity of cell membranes. Vitamin E is essential for the maintenance of the heart function, for functioning of sex organs and for cell protection. It is part of the immune system and protects persons from skin and scar tissue and inflammation.

Vitamin E in food
Vitamin E can be found in vegetable oils, nuts, seeds, soy beans, beans, avocados, margarine, egg yolk, flour, whole grains and green leafy vegetables. All eight forms of vitamin E, including a-tocopherol, occur naturally in food stuffs in varying amounts.

Vitamin E as a supplement
Vitamin E can be used to prevent or aid the treatment of cardiovascular disease, Post Menstrual Syndrome (PMS), menstrual pains, muscle and joint pains, dementia and menopausal troubles. It may also be useful for stroke victims, children with eczema or asthma and premature babies. Extra vitamin E must be taken by people suffering from the flu because a-tocopherol has the ability to enhance antibody formation.

People on blood thinnes should not take vitamin E, because it increases the risk of haemorrhaging. Vitamin E can affect insulin requirements, so it may also be a risk for diabetics.


Vitamin K

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Description Vitamin K
Vitamin K is a fat-soluble vitamin which plays a vital role in blood clotting. There are several forms of vitamin K, one synthesized by plants, one synthesized by animals (including humans) and a large range of types synthesized by bacteria in the small intestine of humans.
Functions of Vitamin K
Vitamin K is essential for the provision of proteins that play a role in blood clotting. Therefore, it is clear that deficiency causes bleeding disorders, such as haemorrhaging (uncontrolled bleeding). This may cause nose bleeds, blood in the urine, or extremely heavy menstrual bleeding. In infants vitamin K deficiency may even result in internal haemorrhaging of the skull. A vitamin K deficiency is fairly uncommon in healthy adults, because bacteria in the intestines synthesize the vitamin. It may however occur in individuals that take medicinal vitamin K antagonists.
Vitamin K in food
Vitamin K is present in cauliflower, soy beans, cottonseed, canola, olives, spinach, Brussels sprouts, broccoli, potatoes, meat, green leafy vegetables and green tea.
Vitamin K as a supplement
Newborns are often vitamin K deficient because they do not have bacteria that produce the vitamin in the gut. This effect is enhanced when the mother takes anti-epileptics.
People that use anti-clotting medication should not take vitamin K. Liver disease results in decreased blood vitamin K levels, which may cause decreased blood clotting resulting in uncontrolled bleeding. Patients that take medication against blood clotting (vitamin K antagonists) must make sure their diets do not contain too much vitamin K. It is advised that vitamin K intake does not exceed 120 µg.

DG01 Project created by Jan Simr (t060084)