Vitamins are organic compounds that are required for life. There are thirteen "essential vitamins", meaning those the body cannot synthesize. These vitamins can either be obtained through eating certain foods, made by exposure to sunlight, or produced by bacteria. They can be found naturally in a large majority of foods such as: grains, fruits, beans, fish, beef, and a large variety of other foods. In addition to naturally occurring vitamins, scientist have been able to create synthetic forms. This means that someone can go to the store and buy vitamins in their pure form.  The essential vitamins are:
- Vitamin A
- B vitamins (thiamine, riboflavin, niacin, pantothenic acid, biotin, vitamin B-6, vitamin B-12 and folate)
- Vitamin C
- Vitamin D
- Vitamin E
- Vitamin K
The word vitamin "vitamine", coined by Polish scientist Cashmir Funk in 1912, comes from the words "vita", meaning life in Italian, and "amine". from thiamine where vitamins were first discovered. However, over the next century the word "vitamine" was shortened to vitamin. If a human did not take any vitamins at all, they would die within a month. This is because vitamins are used by the body to: help clot the blood, assist in chemical reactions, maintain proper health, and perform many other tasks that the body requires.
Since the middle ages, people have known that there were factors in different foods that influenced people's health. However, they did not know what they were or how they worked, they just knew that certain foods would prevent certain diseases. One of the most well known example was aboard ocean going ships. Since ancient times, scurvy was a major hazard on long sea voyages, and nobody knew how to stop the disease. However, in 1747 James Lind began to issue oranges and lemons to sailors, and scurvy was dramatically reduced. However, although his work stopped scurvy on ships it did noting to explain why it worked.
Beginning in 1905, Doctor William Fletcher reached the conclusion that certain factors can prevent people from getting sick. He arrived at this conclusion while trying to find a cure for the disease Beriberi. In his study, he found that when someone eats unpolished rice it prevents the disease, but people who ate polished rice were infected with the disease. He reached the conclusion that a factor is present in the unpolished rice which is essential for good health. Then, in 1906 Sir Frederick Gowland Hopkins, an English biochemist, discovered that certain factors present in food were necessary for good health. Following up on their work, Polish scientist Cashmir Funk named the factors vitamins in 1912.
Over the next fifty years, various scientists discovered that the body requires thirteen vitamins that are essential for life. The last vitamin to be discovered was vitamin B12 in 1948. However, scientists knew about vitamin B12 they just could not discover its chemical structure, as it is the largest vitamin
In addition to discovering the vitamins, scientists began to work on synthesizing them. The majority of the vitamins were created before, or during, the 1950's. However, because of its complex chemical structure, vitamin B12 was not discovered until 1964.
The four fat soluble vitamins are:A, D, E and K. Fat soluble vitamins are dissolved through a layer of fat before they enter the bloodstream. After being transported through the bloodstream the vitamins end up in the liver where they can be stored for long time periods. Because the body stores these vitamins, megadoses of fat soluble vitamins can lead to complications such as: muscle weakness, vomiting, excessive bleeding, dehydration, and other problems. These problems result because the body stores the vitamins rather than eliminating them, which happens to water soluble vitamins. In addition to remaining in the body, the average human requires no extra vitamin supplements because the doses they need are already in a normal diet. Also, the body does not require these vitamins every day and will use the vitamins is has stored in the fat tissues until they need to be used.
Another important difference between the two types of vitamins is the durability of fat soluble vitamins. When the foods that contain vitamins A, D, E and K are washed or cooked the vitamins remain in the food. This factor remains with the vitamins even when they are ingested, because the vitamins will stay in the body for long periods of time, rather than being expelled after one day, as water soluble vitamins are.
Water soluble vitamins include: B-complex and Vitamin C. Vitamins in the B-complex contain eight of the nine water soluble vitamins. These vitamins are fairly easy to destroy, even washing the food that contains them will remove them. In addition to being easily destroyed, these vitamins are not stored in the body. This means that if someone takes a megadose of vitamins the body will excrete them. Water soluble vitamins must be taken each day, because the body will excrete them from the body rather than storing them.
Water soluble, as their name suggests, dissolve in water. After they dissolve, they are immediately used by the body, or are filtered out and placed in urine. While taking a megadose of water soluble vitamins is not recommended, it will not be fatal. However, a lack of water soluble vitamins can quickly kill the individual. This is because water soluble vitamins are essential for life, while fat soluble vitamins are to keep someone healthy.
- Vitamin A-- Improves vision adaption to darkness, regulates gene expression, strengthens immunity, aids growth and embryonic development, and improves red blood cell production. Deficiency results in poor night vision, susceptibility to infections, and possible birth defects.
- Vitamin B6-- Improves nervous system function, red blood cell formation and function, hormone function, and nucleic acid synthesis. Deficiency can result in seizures, abnormal EEG patterns, neurological symptoms (such as irritability, depression, and confusion), inflammation of the tongue, and sores and ulcers of the mouth. 
- Vitamin B12-- Required for the function of the enzyme Methionine Synthase, and the enzyme that catalyzes the biochemical reaction which aids in the production of energy from fats and proteins. Deficiency results in the impairment of these enzymes. 
- Vitamin C-- Required for the synthesis of collagen, helps in the synthesis of the neurotransmitter norepinephrine (critical to brain function and affects mood), required for the synthesis of carnitine, which transports fat to mitochondria, involved in the metabolism of cholesterol, and is a highly effective antioxidant. Deficiency results in scurvy, the symptoms of which include bleeding and bruising easily, hair and tooth loss, joint pain and swelling. 
- Vitamin D-- Necessary for maintaining normal calcium metabolism, immunity, insulin secretion, and blood pressure regulation. Deficiency results in increased risk for osteoporosis and other bone health problems, rickets, and muscle weakness and pain. 
- Vitamin E-- Main function is as an antioxidant, protecting the body from free radicals. Deficiency results in increased risk for cardiovascular disease, cataracts, and cancers thought to result from damage to DNA caused by free radicals. 
- Vitamin K-- Essential for proteins involved in blood clotting, bone mineralization, and cell growth. Deficiency results in impaired blood clotting, usually involving easy bruising or bleeding. 
- Biotin-- Essential for enzymes involved in the synthesis of fatty acids and the formation of glucose from sources other than carbohydrates, and aids in regulation DNA replication and transcription. 
- Folic Acid-- Important for the metabolism of nucleic acids and amino acids. Deficiency results in megaloblastic anemia, which causes a decreased oxygen carrying capacity of the blood, fatigue, weakness, and shortness of breath. 
- Niacin-- Required by 200 enzymes for energy producing oxidation-reduction reactions, and appears to aid in DNA repair and stress responses. Deficiency results in a condition called pellagra, the symptoms of which are a dark, scaly skin rash, a bright red tongue, vomiting, diarrhea, apathy, depression, disorientation, and memory loss. 
- Pantothenic Acid-- Necessary for chemical reactions that generate energy from food (fat, carbohydrates, and proteins), the synthesis of essential fats, cholesterol, and steroid hormones, and metabolism of a number of drugs and toxins by the liver. Some symptoms of deficiency are headache, fatigue, insomnia, intestinal disturbances, and numbness and tingling of their hands and feet. 
- Riboflavin-- Necessary for energy producing redox reactions, and acts as an antioxidant. Symptoms of deficiency are sore throat, redness and swelling of the lining of the mouth and throat, cracks or sores on the outsides of the lips and at the corners of the mouth, inflammation and redness of the tongue, a moist, scaly skin inflammation, the formation of blood vessels in the clear covering of the eye, and decreased red blood cell count. 
- Thiamin-- A required coenzyme for a few important enzymes involved in the production of energy from food and the synthesis of nucleic acids, DNA, and RNA. Deficiency can result in Dry Beriberi, which involves peripheral neuropathy, "burning feet syndrome", and weakness in arms and legs, or Wet Beriberi, which involves rapid heart rate, enlargement of the heart, and difficulty breathing. 
- Vitamin A is found in: cod liver oil, sweet potato, pumpkin, carrot, cantaloupe, spinach, kale, collard, and butternut squash. The body requires from 300 mcg/day in children to 900 mcg/day in adult men and 700 mcg/day in adult women.
- Vitamin B6 is found in: fortified cereal, banana, wild salmon, turkey without skin, chicken (light meat), potato, and spinach. The body requires from 0.1 mg/day in children to 1.7 mg/day in adult men and 1.5 mg/day in adult women.
- Vitamin B12 is found in: clams, mussels, crab, salmon, rockfish, beef, egg, milk, and Brie cheese. The body requires from 0.4 mg/day in children to 2.4 mg/day in adults.
- Vitamin C is found in: oranges, grapefruit, strawberries, tomato, sweet red pepper, broccoli, and potato. The body requires from 15 mg/day in children to 90 mcg/day in adult men and 75 mcg/day in adult women. Smokers should take about 35% more Vitamin C than the average adult.
- Vitamin D is found in: salmon, sardines, mackerel, fortified milk, fortified soy milk, and egg yolk. The body requires from 5 mcg/day in children to 10 mcg/day in adults men, 15 mcg/day for the elderly.
- Vitamin E is found in: olive oil, soybean oil, corn oil, canola oil, safflower oil, sunflower oil, almonds, hazelnuts, peanuts, and avocado. The body requires from 4 mg/day in children to 15 mg/day in adults.
- Vitamin K is found in: soybean oil, canola oil, broccoli, kale, spinach, leaf lettuce, Swiss chard, watercress, and parsley. The body requires from 30 mcg/day in children to 120 mcg/day in adult men and 90 mcg/day in adult women.
- Biotin is found in: yeast, egg, cheddar cheese, liver, pork, salmon, and avocado. The body requires from 5 mcg/day in children to 30 mcg/day in adults.
- Folic Acid is found in: orange juice, spinach, asparagus, lentils, garbanzo beans, lima beans, bread, pasta, and rice. The body requires from 65 mcg/day in children to 400 mcg/day in adults.
- Niacin is found in: chicken (light meat), turkey (dark meat), beef, salmon, tuna, bread, cereal, pasta, peanuts, lentils, and lima beans. The body requires from 2 mg/day in children to 16 mg/day in adult men and 14 mg/day in adult women.
- Pantothenic Acid is found in: chicken, egg, milk, yogurt, broccoli, lentils, split peas, avocado, sweet potato, raw mushrooms, and lobster. The body requires from 1.7 mg/day in children to 5 mg/day in adults.
- Riboflavin is found in: fortified cereal, milk, cheddar cheese, eggs, almonds, salmon, chicken (dark meat), beef, broccoli, asparagus, and spinach. The body requires from 0.3 mg/day in children to 1.3 mg/day in adult men and 1.1 mg/day in adult women.
- Thiamin is found in: lentils, peas, long grain brown rice, long grain white rice, whole wheat bread, fortified breakfast cereal, pork, Brazil nuts, pecans, orange, cantaloupe, and milk. The body requires from 0.2 mg/day in children to 1.2 mg/day in adult men and 1.1 mg/day in adult women.
The amount of daily vitamins needed increases significantly in females who are pregnant or nursing. 
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