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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. (2)
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. (3) 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 muck 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. (5) 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 (溶解脂肪的) and the
water-soluble (溶解水的) 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.