Vitamins are non-caloric organic compounds required in very small quantities by the body for healthy growth and development. Vitamins aid in nutrient digestion, absorption, metabolism and utilization, and when missing from a diet, deficiency diseases develop. Each vitamin has unique functions to perform, both individually and in concert with other vitamins. Vitamins are classified as either water- or fat-soluble.
Classification
Vitamins are classified on the basis of solubility, either water- or fat soluble. Vitamin precursors are also found in food. These precursors are chemicals that are turned into active vitamins once inside the body. Water soluble vitamins travel extensively throughout the body via the bloodstream. Because they are not stored to any great extent, excesses are excreted in the urine. Vitamins C and the B vitamins are examples of water-soluble vitamins. The fat-soluble vitamins, including A, D, E and K, can be stored in body tissues, however.
Water Soluble B-Vitamins
B vitamins are constituents of coenzymes, chemicals in the body that activate enzymes. The B vitamins help to convert carbohydrates, proteins and fats from food into usable energy. Thiamine, riboflavin, niacin, folate, vitamin B-6, vitamin B-12, pantothenic acid and biotin are all examples of B vitamins. Thiamine plays a critical role in nerve transmission. Riboflavin functions in eye and skin health. Niacin is a precursor for tryptophan, an amino acid that is a building block of protein molecules. Folate is critical for nervous system health, as is vitamin B-12. Vitamin B-6 is involved in protein and serotonin synthesis and red blood cell formation. Pantothenic acid plays a part in lipid, steroid, neurotransmitter and hemoglobin manufacture. Biotin is needed for fat synthesis.
Water Soluble Vitamin C
Vitamin C functions as an antioxidant and is essential for forming the connective tissues of tendons, ligaments, bones, skin and teeth. Vitamin C also aids in iron absorption, hormone synthesis and vitamin E activation.
Fat Soluble Vitamins
Vitamins A, D, E and K are fat-soluble vitamins. Found in the fat and oily portion of food, they are initially absorbed and then stored in the liver and body fat tissues until needed. At excessive intake levels, toxicities can develop. Deficiencies can occur when dietary fat intake is very low.
Vitamin A is integral to proper vision, immunity, reproduction and protein synthesis. Vitamin D is unique because in addition to being found in food, it is synthesized by the body when in direct sunlight. Vitamin D maintains proper blood calcium and phosphorus levels, supporting healthy bone growth. Vitamin E is an antioxidant that protects lipids from harmful oxidation. Vitamin K plays a role in synthesizing blood clotting proteins as well as important bone proteins.
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