Essential to the proper functioning of the human body, vitamins are accountable for maintaining a normal metabolism as well as proper cellular growth and development. Vitamins are divided into two categories: fat-soluble and water-soluble. Vitamins A, D, E, and K are the four fat-soluble vitamins with the others falling into the water-soluble category. If a vitamin is fat soluble, that means it can be stored in fat and used at a later date. Water-soluble vitamins must be used immediately (excess is expelled via urine).

Each vitamin serves a specific purpose within the human body. A deficiency in vitamins may lead to various health issues while possibly increasing your risk for conditions like heart disease, various cancers, and osteoporosis (weak bone density).

A list of vitamins:

Commonly known as retinol or carotenoids, vitamin A is responsible for a variety of bodily functions and process ranging from healthy skin to bone growth to various cellular functions. It is found in a variety of foods ranging from animal based sources like eggs, meat, and cheese to vegetable based sources like carrots, sweet potatoes and broccoli.
Used primarily to create energy in the body, vitamin B1 (thiamin) is essential for metabolic processes. Located mainly in whole grains and enriched bread/flour products, it is usually quite rare for one to be deficient in this vitamin.
Working together with vitamin B9, vitamin B12 (cobalamin) supports red blood cell formation, healthy nerve cells, aids in the production of DNA and RNA, and is commonly found in animal products such as fish, dairy, eggs, beef, and pork.
Partially responsible for releasing energy from carbohydrates as well as healthy skin and hair, riboflavin is found in a range of foods including milk, eggs, nuts, green veggies, and enriched flour/bread products.
Playing a role in energy production in addition to normal digestion, healthy skin, hair, eyes, and the liver, vitamin B3 (niacin) is found in a variety of foods while improving circulation. It also aids the body in producing hormones related to sex and stress.
Required to synthesize cholesterol, vitamin B5 (pantothenic acid) is a water soluble vitamin that is also used to produce hormones and found in foods such as avocado, broccoli, beans, meats, and whole-grain breads and flours.
One of the more important B vitamins, vitamin B6 (pyridoxine) is used in making antibodies to fight disease as well as maintain normal nerve function among other bodily functions. Found often foods such as avocado, banana, legumes, meats, whole grains, and enriched bread/flour products.
Required for bodily growth, this water-soluble vitamin is often found in cereal, chocolate, egg yolk, milk, nuts, and meat products.
Immensely responsible for proper brain function and the production of DNA and RNA, vitamin B9 (folic acid) is known to greatly reduce potential birth defects. This vitamin is found a large variety of foods.
Vital in the healing of wounds and boosting the immune system, vitamin C (ascorbic acid) is a water-soluble vitamin that is most often found in oranges and other citrus foods.