B vitamins are a group of water-soluble vitamins that play important roles in cell metabolism. The B vitamins were once thought to be a single vitamin, referred to simply as vitamin B. Later research showed that they are chemically distinct vitamins that often coexist in the same foods.
In general, supplements containing all eight B vitamins are referred to as a vitamin B complex. Individual B vitamin supplements are referred to by the specific name of each vitamin (e.g., B1, B2, B3 etc.).
The following lists all B vitamins:
B vitamins are found in whole unprocessed foods. Processed carbohydrates such as sugar and white flour tend to have lower B vitamin than their unprocessed counterparts. For this reason, it is required by law in most countries that the B vitamins thiamine, riboflavin, niacin, and folic acid be added back to white flour after processing. This is sometimes called "Enriched Flour" on food labels. B vitamins are particularly concentrated in meat such as turkey, tuna and liver. Good sources for B vitamins include whole grains, potatoes, bananas, lentils, chili peppers, tempeh, beans, nutritional yeast, brewer's yeast, and molasses.
The B12 vitamin is of note because it is not available from plant products, making B12 deficiency a legitimate concern for vegans and vegetarians. A popular means of increasing one's vitamin B intake is through the use of dietary supplements.
Because they are soluble in water, excess B vitamins (such as may be ingested via supplements) are generally readily excreted, although individual absorption, use and metabolism may vary…" The elderly and athletes may need to supplement their intake of B12 and other B vitamins due to problems in absorption and increased needs for energy production. In cases of severe deficiency B vitamins, especially B12, may also be delivered by injection to reverse deficiencies. Both type 1 and type 2 diabetics may also be advised to supplement thiamine based on high prevalence of low plasma thiamine concentration and increased thiamine clearance associated with diabetes. Also, Vitamin B9 (folic acid) deficiency in early embryo development has been linked to neural tube defects. Thus, women planning to become pregnant are usually encouraged to increase daily dietary folic acid intake and/or take a supplement.