B vitamins
Water-soluble vitamins essential for metabolism and red blood cells.
B vitamins are a class of water-soluble vitamins that play important roles in cell metabolism and synthesis of red blood cells. They are a chemically diverse class of compounds. Dietary supplements containing all eight are referred to as a vitamin B complex. Individual B vitamins are referred to by B-number or by chemical name, such as B1 for thiamine, B2 for riboflavin, and B3 for niacin, while some are more commonly recognized by name than by number, such as pantothenic acid (B5), biotin (B7), and folate (B9).
- field
- Nutrition, Biochemistry
- known_for
- Essential cofactors and precursors for key metabolic processes and red blood cell synthesis
- key_fact
- Each B vitamin is either a cofactor (generally a coenzyme) for key metabolic processes or is a precursor needed to make one.
- deficiency_risk
- B12 deficiency is a legitimate concern for those maintaining a vegan diet.
Lore & Background
B vitamins are found in abundance in meat, eggs, and dairy products. Processed carbohydrates such as sugar and white flour tend to have lower B vitamin content than their unprocessed counterparts. For this reason, it is common in many countries (including the United States) that the B vitamins thiamine, riboflavin, niacin, and folic acid are added back to white flour after processing, referred to as 'enriched flour' on food labels. B vitamins are particularly concentrated in meat such as turkey, tuna and liver. Sources also include spinach, legumes, whole grains, asparagus, potatoes, bananas, chili peppers, and breakfast cereals.
Reader's Guide
B vitamins are significant because they serve as cofactors or precursors for essential biochemical reactions, including the catabolic release of free energy to power cellular activity. FAD, NAD+, and coenzyme A are essential for catabolism; tetrahydrofolate is necessary for synthesizing amino acids like glycine; and heme B holds iron in hemoglobin for oxygen transport. Deficiencies can lead to named vitamin deficiency diseases or other symptoms. Because B vitamins are water-soluble, excess is generally excreted, though absorption and metabolism vary. The elderly and athletes may need supplementation due to absorption problems or increased energy needs. Severe deficiencies, especially B12, may be treated by injection. Folate deficiency in early embryo development has been linked to neural tube defects, so women planning pregnancy are encouraged to increase folate intake. Many substances once assigned B-numbers (e.g., B4, B8, B10, B11) are no longer considered vitamins, either because they are synthesized by the body or are not essential for life.
Did You Know?
- The B12 vitamin is not abundantly available from plant products, making B12 deficiency a concern for vegans.
- Standard USP method for measuring B12 content measures bacterial response, not B12 directly, which can over-report B12 in plant sources.
- Folate deficiency in early embryo development has been linked to neural tube defects.
- Substances once thought to be vitamins, such as choline (B4) and amygdalin (B17), were disqualified as vitamins.
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