Vitamins B6 and B12 are water-soluble vitamins that exist in several forms, but B12 is unique in that it contains the mineral cobalt. A well-balanced diet should provide sufficient amounts of both vitamins, which is important for the roles they play in metabolism, energy and cell growth.
Functions
Vitamins B6 and B12 have essential roles in red blood cell metabolism, fat and protein metabolism, nervous system function and the synthesis of nucleic acids. Vitamin B6 is needed for the conversion of stored carbohydrates to glucose. Vitamin B12 must be present for the production of DNA, RNA and some hormones.
Requirements
The recommended daily allowance for vitamin B6 is 1.3 mg/day for adults ages 50 and younger. Women older than 50 should have 1.5 mg/day and men should consume 1.7 mg/day. Women who are pregnant should increase their recommended daily allowance to 1.9 mg/day and those who are breastfeeding should receive 2.0 mg/day. The recommended daily allowance for vitamin B12 is 2.4 micrograms (mcg)/day for all adults except women who are pregnant (2.6 mcg/day) and breastfeeding (2.8 mcg/day).
Sources
Vitamin B6 is available from a variety of foods, such as fortified cereals. Good fruit and vegetable sources include a baked potato (0.7 mg), a medium banana (0.68 mg), ½ cup spinach (0.14 mg), 6 oz. tomato juice (0.2 mg) and ½ cup lima beans (0.10 mg). Three ounces of chicken, pork or beef provide between 0.42 to 0.52 mg, while salmon and tuna have 0.18 to 0.19 mg.
The only dietary sources of B12 are animal products, such as meat, poultry, fish and milk. Clams are the highest source of B12, with 84 mcg per 3-oz. serving. Some of the best fish and meat sources (a 3-oz portion) include crab (8.8 mcg), salmon (2.4 mcg), beef (2.1 mcg) and chicken (0.3 mcg). One egg provides 0.6 mcg and 8 ounces of milk contain 0.9 mcg.
Deficiency
The National Institute of Health states that B6 deficiency is rare in the United States and usually found only in individuals consuming a diet deficient in many nutrients. However, some antituberculosis and antiparkinsonian medications can interfere with the absorption of B6. Symptoms of B6 deficiency---skin inflammation, sore tongue, depression and confusion---occur only after too little B6 is consumed for a long time. A deficiency in B6 can impact the body's ability to absorb vitamin B12.
Vitamin B12 deficiency occurs in about 10 to 15 percent of adults over the age of 60, according to LPI. Deficiency is typically caused by malabsorption. The stomach must secrete sufficient acids and enzymes to ensure B12 is absorbed from food. Any condition that interferes with the production of stomach acid, such as chronic gastritis and pernicious anemia, decreases its absorption. Fatigue, constipation, weight loss, depression, confusion, and sometimes numbness in hands or feet are symptoms of B12 deficiency.
Considerations
Homocysteine is an amino acid that is needed for metabolism and protein synthesis, but studies indicate that high levels of homocysteine increase the risk of cardiovascular disease, states information from LPI. Three vitamins---folate, vitamin B6 and vitamin B12---regulate the amount of homocysteine found in the blood. If your diet is deficient in these vitamins, or if your body does not absorb them properly, levels of homocysteine will increase. Over time, too much homocysteine damages the blood vessels and increases the risk of blood clots.
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