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B vitamins are a group of related vitamins that are essential to body function. Each acts both independently and together with other B vitamins to assist chemical reactions in the body. Due to their interdependence, B vitamins are often discussed as a group. In fact, when first discovered, they were thought to be one vitamin.

Vitamins are organic compounds obtained from dietary sources and necessary for good health. Their existence was first recognized in the early 20th century and their letter names correspond to the order in which they were discovered. When individual B vitamins were discovered, they were assigned numbers. Later names were given for each that relate to their chemical formulas.

B vitamins come from many sources and a balanced diet will typically fulfill the body’s needs. They are also available as supplements, both as individual vitamins and as the entire B-complex group.

Vitamins are water-soluble or fat-soluble molecules, which determines how they travel through the body and how they are stored. Being water-soluble, most B vitamins move freely through the body and cells. They are not stored in tissues and must be consumed or manufactured by the body regularly.

Inside cells, B vitamins act as coenzymes, compounds that make many chemical reactions within the body possible. Some of the reactions utilizing B vitamins are necessary for growth and the metabolism of carbohydrates, fats and proteins. In addition to their involvement in chemical reactions, some B vitamins are structural components of cells, such as B1 in the myelin sheath of nerve cells.

B vitamins are essential, meaning that the body either does not produce them itself or does not produce enough to meet its needs. The body is able to produce small amounts of B3, B5, folate (B9), biotin and choline. Most B vitamins are used and quickly eliminated from the body. The exception is vitamin B12, which the body is able to recycle and reuse.

The body’s ability to absorb several of the B vitamins through the gastrointestinal tract diminishes with age. Therefore, physicians often recommend supplements or fortified foods for patients over age 50. Vitamins in these products are in forms that are often easier to absorb than those that occur naturally. Supplements may also be recommended for vegetarians or vegans to replace those B vitamins that are naturally available only in animal products.

Because B vitamins work in complex interrelationships, a deficiency of one may impact the function of others. While this may initially cause only mild symptoms, it can frequently progress to serious or even life-threatening conditions. In industrialized nations, vitamin B deficiencies are rare because adequate intakes are easily achieved with a balanced diet.