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The B vitamins are available from a variety of dietary sources. Therefore, a balanced diet usually provides sufficient vitamin B to satisfy the needs of the human body.

Natural Sources of B Vitamins

In addition to naturally occurring nutrients, some foods have them added during processing. Such products are called enriched foods or fortified foods, and the process frequently includes many of the B vitamins. These foods include many bread, rice, cereal and yeast products. Such foods are often critical in a vegetarian or vegan diet to provide non-animal sources of B vitamins that are naturally found only in animal products.

While many foods are good sources of B vitamins, the way those foods are prepared can affect their nutrient content. B vitamins can be destroyed during food preparation and processing, including:

• Boiling. B vitamins are water-soluble. Therefore many leach out of foods and into cooking water when boiled.
  
  
• Overcooking. Vitamins B1, B5, B6 and folate are vulnerable to heat and may be destroyed if cooked at too high a temperature or for too long.
  
  
• Exposure to oxygen. Folate is vulnerable to air exposure and it may be lost when cut vegetables are allowed to sit long periods.
  
  
• Exposure to light. Light destroys vitamin B2, part of the reason milk is often sold in semi-translucent plastic bottles or cardboard boxes.
  
  
• Freezing, canning and refining. These processes can destroy vitamin B5.
  
  
• Microwave cooking. Aside from issues of heat and water leaching, B12 is unique among the B vitamins because it can be destroyed by microwave cooking.

In most industrialized nations, the average diet contains sufficient B vitamins to meet the body’s needs. Under certain conditions, a physician may recommend vitamin supplements if the patient’s system is unable to use or absorb the nutrients from food sources. The B vitamins are often grouped together in one dose in B complex supplements, which may also contain other compounds that may be of benefit. Most widely available multivitamins also include sufficient quantities of the B complex.

Oral supplements are also available for some individual B vitamins, including B3, B6, folic acid and B12. Other forms of B12 are also available for patients unable to absorb the nutrient through the stomach (e.g., injection, nasal gel).

Differences in the body’s ability to absorb or synthesize some B vitamins from foods and supplements make measuring their vitamin content complex. Nutritional scientists have developed ways to compare the quantities available. These include:

• Niacin equivalents (NE). Nutritional information for foods expresses the amount of B3 available as niacin equivalents. This is the total B3 available directly plus the amount the body can make from the amino acid tryptophan. Each NE equals one milligram (mg) of niacin or 60 mg of tryptophan.
  
  
• Dietary folate equivalents (DFEs). Dietary supplement labels include the amount of folate as dietary folate equivalents. This is because the body is able to use synthetic folic acid more efficiently than folate from food. The DFE is determined by multiplying the micrograms (µg) of synthetic folic acid present, then adding the (µg) of food folate.