Vitamins

Vitamins are organic compounds that the body needs for the maintenance of good health and for growth. By convention, the name vitamin is reserved for certain nutrients that the body cannot manufacture and therefore must get from food.

Vitamins contain no useful energy for the body but they do link and regulate the sequence of metabolic reactions that release energy within the food we consume. Vitamins cannot be made in the body and must be obtained in our diet. A well balanced diet provides an adequate quantity of all vitamins regardless of age and level of physical activity.

The two types of vitamins are classified by the materials in which they will dissolve. Fat-soluble vitamins -- vitamins A, D, E and K -- dissolve in fat before they are absorbed in the blood stream to carry out their functions. Excesses of these vitamins are stored in the liver. Because they are stored, they are not needed every day in the diet.

By contrast, water-soluble vitamins dissolve in water and are not stored; they are eliminated in urine. We need a continuous supply of them in our diets. The water-soluble vitamins are the B-complex group and vitamin C. In contrast to the fat-soluble vitamins, the water-soluble vitamins are not easily stored by the body. They are often lost from foods during cooking or are eliminated from the body.

Fat soluble vitamins should not be consumed in excess as they are stored in the body and an excess can result in side effects. An excess of vitamin A may result in irritability, weight loss, dry itchy skin in children and nausea, headache, diarrhea in adults.

An excess of water soluble vitamins should not result in any side effects as they will disperse in the body fluids and voided in the urine.

Water Soluble Vitamins

B-complex vitamins and vitamin C are water-soluble vitamins that are not stored in the body and must be replaced each day. There are eight of them, namely; B1 (thiamine), B2 (riboflavin), B6 (pyridoxine), niacin (nicotinic acid), B12, folic acid, pantothenic acid, and biotin. The water-soluble vitamins, inactive in their so-called free states, must be activated to their coenzyme forms.

The water-soluble vitamins are absorbed in our intestine, pass directly to the blood, and are carried to the tissues in which they will be utilized. Vitamin B12 requires a substance known as “intrinsic factor for absorption".

Water-soluble vitamins usually are excreted in the urine on a daily basis. Thiamine (B1), riboflavin (B2), pyridoxine (B6), ascorbic acid (C), pantothenic acid, and biotin appear in urine as free vitamins Tissue storage capacity of water soluble vitamins is limited and, as the tissues become saturated, the rate of excretion increases sharply. This keeps us from overdosing but this is also why we need to take these vitamins daily. Unlike the other water-soluble vitamins, however, vitamin B12 is excreted solely in the feces. Some folic acid and biotin is also normally excreted in this way. Although fecal excretion of water-soluble vitamins (other than vitamin B12, folic acid, and biotin) occurs, their source probably is the intestinal bacteria, which synthesize the vitamins, rather than vitamins that we have eaten and used.

The effects of the water-soluble vitamins are obvious in many parts of the body. They act as coenzymes to help the body obtain energy from food. They also are important for normal appetite, good vision, healthy skin, healthy nervous system and red blood cell formation.
We need a continuous supply of them in our diets to ensure proper health and nutrition.

Fat Soluble Vitamins

Fat-soluble vitamins are absorbed, together with fat from the intestine, into the circulation. Once absorbed into the circulation these vitamins are carried to the liver where they are stored.
Vitamins A, D, E and K make up the fat soluble vitamins. Vitamins A, D and K are stored in the liver and vitamin E is distributed throughout the body's fatty tissues.

This storage capability makes the fat-soluble vitamins potentially toxins. Care should be exercised when taking the fat-soluble vitamins. The fat-soluble vitamins, especially vitamin A, should be consumed with care because of their storage capabilities. They have the potential of building up to harmful levels.

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