Sources & Functions Of Vitamins

Vitamins are substances required by the body in minute amounts. A lack of any of the essential vitamins results in characteristic deficiency symptoms that disappear when vitamin intake returns to normal. Some vitamins can have different structures, but the same biological and chemical activity. These forms are referred to as vitamers. There are two main classes of vitamins: those that are soluble in fat and those that are soluble in water.

Fat-Soluble Vitamins

The fat-soluble vitamins are vitamin A, D, E and K. Vitamin A is important for night vision and healthy eyes, is essential for the growth and specialization of cells, promotes a healthy immune system and keeps skin and mucus membranes healthy. Animal sources of vitamin A are liver, milk, and eggs, while plant sources include dark green and orange vegetables such as carrots and kale and orange fruits such as peaches.

Vitamin D is integral in the regulation of calcium levels in the body and thus plays important roles in bone health. It is synthesized under the skin upon exposure to sunlight; however, you also get vitamin D from egg yolks, fish oils and fortified foods such as milk and margarine.

Vitamin E functions as an antioxidant and protects cells from damage caused by free radicals. Sources of this vitamin include vegetable oils, nuts and green leafy vegetables.

The fourth fat-soluble vitamin is vitamin K, and it is essential for blood to clot. Bacteria in the human gut can synthesize some vitamin K and food sources of this vitamin include green leafy vegetables such as spinach and kale, and meat, eggs and dairy.

Vitamin C

Vitamin C is a water-soluble vitamin that is required to form the connective tissue collagen. Hence it is important in the formation of healthy gums, teeth, bones and blood vessels. Vitamin C is an important antioxidant, helps to absorb iron and calcium from foods, and aids wound healing. According to a review in the May 2009 issue of the "Journal of the American Academy of Nurse Practitioners," supplementing with vitamin C may reduce the duration of the common cold; however, it is not effective in preventing its occurrence or in reducing the severity of the symptoms. Foods rich in vitamin C are oranges, grapefruit, kiwi, bell peppers, tomatoes, broccoli and spinach.

Thiamin, Riboflavin and Niacin

Thiamin, riboflavin and niacin, also known as vitamins B1, B2 and B3, respectively, are all involved in the metabolism of foods into energy. Furthermore, thiamine and niacin are important in nerve function, while riboflavin also plays a role in red blood cell production and healthy vision. Thiamin is found in meat, whole grains, potatoes and kale, riboflavin is found in meat, eggs, legumes, nuts, dairy products and broccoli, and niacin is found in meat, poultry, fish and peanuts.

Vitamin B6, B12, Panthothenic Acid, Folate and Biotin

Vitamin B6 is essential for protein metabolism, nervous system function and in red blood cell production and is found in high amounts in whole grains, meat, fish and poultry and bananas.

Vitamin B12 is also important in nervous system function and red blood cell production. Further roles of this vitamin are in the breakdown of fatty acids and in the metabolism of folate. Foods containing B12 include meat, fish, poultry, and dairy products. Plants are not a source of vitamin B12.

Panthothenic acid and biotin are both widespread in foods and thus deficiencies are very rare. Panthothenic acid is used to synthesize coenzyme A which is important in energy metabolism and in the synthesis of acetylcholine and cholesterol. Biotin is involved in the metabolism of fatty acids and amino acid, and in cell growth.

Folate is necessary for normal DNA and RNA synthesis and thus cell division. According to the "Manual of Dietetic Practice," deficiency of folate leads to megaloblastic anemia, and if a mother is not consuming sufficient folate during conception and early pregnancy, the fetus is at an increased risk of suffering for neural tube defects. Important sources of folate include green leafy vegetables, legumes, orange juice, and fortified breakfast cereals.