Vitamins are essential to human life. Among their many roles, they are involved in growth, the release of energy from foods, cellular reproduction, the immune system and vision. Without them, the body is unable to process food into energy or pass genetic information to new cells.

The first vitamins were not discovered by scientists until the early 20th century. They were found to be the components of certain foods known to help prevent or cure several diseases (such as limes, which help prevent scurvy). The commonly recognized vitamins include:

• Vitamin A
• B vitamins (e.g., B1, B2, B3, B9, B12)
• Vitamin C
• Vitamin D
• Vitamin E
• Vitamin K

Vitamins are classified by how they are absorbed by the body. Water-soluble vitamins (the B vitamins and vitamin C) can be absorbed directly into the blood from food passing through the alimentary canal. Fat soluble vitamins (vitamins A, D, E and K) need special molecules to escort them into the bile before they can move into the bloodstream and be used or stored in fat cells. The solubility also affects how they are stored in the body and which foods they can be found in.

Consuming a balanced diet will fulfill the body’s vitamin needs. This diet should include fruits and vegetables, whole grains, legumes, meats and dairy products. In addition, enriched foods and fortified foods have vitamins added and can replace many food groups that may be avoided due to medical conditions (e.g., milk intolerance) or ethical concerns (e.g., a vegan diet). When dietary sources are unable to provide sufficient vitamins, supplements are available. The use of supplements should only be done with the guidance of a physician, especially for people who belong to certain population groups, such as pregnant or breastfeeding women.

Vitamin deficiencies are rare in the United States and other industrialized nations. Most tend to occur in conjunction with other conditions (e.g., alcoholism). Resulting diseases include beriberi, scurvy and rickets.