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The B vitamins are involved in chemical processes that take place throughout the body. All are involved directly or indirectly in energy metabolism and growth. The nine B vitamins and their functions are:

• B1 (thiamine). Found on the myelin sheath of nerve cells and aids communication between nerves and muscles, including the heart. Each cell depends on B1 to help convert carbohydrates to energy. B1 also plays a role in the production of hydrochloric acid, making chemical digestion of food possible.
  
  
• B2 (riboflavin). Like vitamin B1, B2 helps release energy from carbohydrates. It is also involved in breaking down fats and proteins. B2 is necessary for cell development and function, and may also play a role in producing red blood cells.
  
  
• B3 (niacin, niacinamide, nicotinic acid or nicotinamide). Helps metabolize glucose, fat and alcohol. B3 is also needed by the body to make new cells and create fatty acids and steroids. The forms found naturally in food are nicotinic acid and nicotinamide. Niacin and niacinamide are used in dietary supplements, which may be prescribed in large doses to reduce low density lipoproteins (the “bad cholesterol”) and increase high density lipoproteins (the “good cholesterol”). B3 is one of the few B vitamins that the body can produce (from the amino acid tryptophan), although in smaller amounts than it needs.
  
  
• B5 (pantothenic acid). Involved in more than 100 metabolic pathways for the conversion of carbohydrates, proteins and fats. B5 is also necessary to make lipids, neurotransmitters and hemoglobin. The body produces some B5 itself, but not enough to meet its needs.
  
  
• B6 (pyridoxine, pyridoxal or pyridoxamine). Involved in many body processes, including making amino acids, converting tryptophan to B3 and maintaining blood glucose levels. In the nervous system, it is necessary for the synthesis of the neurotransmitters serotonin, dopamine, and norepinephrine, which influence mood and appetite. Within the circulatory system, B6 is required to make hemoglobin.
  
  
• B9 (folate or folic acid). Necessary to create and maintain cells because of its involvement in the synthesis of proteins and DNA (which controls cell function and transfers genetic information to the next generation of cells). B9 is essential in the earliest stages of pregnancy for fetal health due to its role in preventing neural tube defects in infants. Folic acid is the synthetic form of the vitamin and is more easily absorbed than the natural form. Folate can be produced by the body, but not in amounts large enough to meet the body’s needs.
  
  
• B12 (cobalamin). The only B vitamin that requires a specific chemical (intrinsic factor [IF]) to be absorbed into bloodstream. B12 is essential for the nervous system, creation of red blood cells and making DNA. It is also part of a coenzyme involved in the metabolism of amino acids and fatty acids.
  
  
• Biotin (sometimes called vitamin B7). Involved in metabolism of some fatty acids and amino acids. It is also involved in the synthesis of glucose. Biotin is made by bacteria in the gastrointestinal tract, but not enough is produced to meet the body’s needs.
  
  
• Choline. Involved in fat metabolism and transport. It is also necessary for the synthesis of several neurotransmitters. The human body is able to make this compound, but it is not known whether the body makes enough to meet its needs. While it may actually be a nonessential vitamin, it is most typically classed with other B-complex vitamins as essential.

The National Academy of Sciences (NAS) established dietary reference intakes (DRIs) to maintain a healthy body. The recommendations are categorized by gender and age. The suggestions for women also incorporate pregnancy and breastfeeding. For some age groups and vitamins there is scientific uncertainty as to what intake is necessary for daily function. For these groups, the NAS provides adequate intakes (AIs). AIs provide the mean intake of breastfed infants (children younger than 12 months) and the minimum to prevent deficiency of the vitamins B5, biotin and choline.

For the B vitamins, the recommendations are measured in either milligrams per day (mg/d) or micrograms per day (¼g/day).

Vitamin B DRI Recommendations: Males

Vitamin B DRI Recommendations: Females

Vitamin B DRI Recommendations: Children