Vitamins
Vitamins are organic compounds which are present in certain foods and are essential to the health of men and other animals.
1
Without these substances, the breakdown and absorption of foods could not occur. Certain vitamins participate in the formation of blood cells, hormones, nervous system chemicals, and genetic materials.
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Fat-soluble vitamins include vitamins A, D, E and K. The water-soluble vitamins include Vitamin C and the B-vitamin complex.
Fat-soluble vitamins are usually absorbed with foods that contain fat. Excessive amounts of these vitamins are stored in the body"s fat, the liver and kidneys. Because fat-soluble vitamins can be stored, they do not have to be consumed every day.
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A deficiency of Vitamin A leads to skin changes and night blindness, or failure of the eye to adapt to the dark. Vitamin A can be obtained directly from foods of animal origin such as milk, eggs, and liver.
4
Vitamin D acts much like a hormone and regulates calcium and phosphorus absorption and metabolism. Some Vitamin D is obtained from such foods as eggs, fish, liver, butter, and milk. But humans get most of their Vitamin D from exposure of the skin to sunlight. A deficiency of Vitamin D leads to bone problems.
The role of Vitamin E in the human body has not been established.
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Vitamin E is found in seed oil and wheat.
Vitamin K is necessary for the clotting of blood. It is produced in sufficient quantities by bacteria in the intestine, but is also provided by leafy green vegetables and eggs.
The water-soluble vitamins, C and B complex, cannot be stored and therefore need to be consumed daily to satisfy the body"s needs. Vitamin C is important in the formation and maintenance of connective tissue. It protects gums, skin, and mucous membranes. It is mainly found in fruits like oranges.
B-complex vitamins serve a wide range of important metabolic functions and prevent some diseases. They are found mostly in the liver.
A. Vitamins are classified into two groups, that is, the fat-soluble (脂溶性的) and the water-soluble (水溶性的) vitamins.
B. Their functions are mainly to enhance the metabolism (新陈代谢) of proteins and fats.
C. It is necessary for a healthy life.
D. Vitamin A is essential for normal growth and for the health of epithelial cells.
E. It has been popularly advocated for a great variety of diseases, but no clear evidence exists that it eases any specific disease.
F. Vitamin A can also be obtained through eating green and yellow fruits and vegetables.