A water-soluble vitamin that's naturally present in some foods, vitamin B-12 is needed for the formation of red blood cells, the synthesis of DNA and proper neurological function. Vitamin B-12 contains the mineral cobalt, resulting in the term cobalamin used to refer to several B-12 compounds. The best way to ensure you have a healthy level of vitamin B-12 is to obtain enough in your diet.
Recommended Intake
Healthy levels of vitamin B-12 can be maintained by consuming the recommended dietary allowance, or RDI, which is the daily amount needed to meet the requirements of 98 percent of all healthy individuals, according to the National Institutes of Health Office of Dietary Supplements. The RDI for ages 4 to 8 is 1.2 mcg. Nine- to 13-year-olds should have 1.8 mcg, and everyone over the age of 14 should have 2.4 mcg of vitamin B-12 daily. Women who are pregnant or breast-feeding should increase their daily intake to 2.6 and 2.8 mcg, respectively.
Absorption
Whether the source of vitamin B-12 is food or a supplement, healthy levels in your body depend on proper absorption during digestion. This process depends on a protein secreted in the stomach called intrinsic factor. Insufficient intrinsic factor results in a deficiency of vitamin B-12. Even in healthy individuals, only about 10 mcg of a 500 mcg oral supplement is typically absorbed, according to the Office of Dietary Supplements.
Deficiency
Low levels of vitamin B-12 are usually due to pernicious anemia or malabsorption. Other causes include gastritis, surgical resection of the stomach or small intestine, diseases of the pancreas and acquired immunodeficiency syndrome. Symptoms differ depending on the cause but may appear as diarrhea or constipation, fatigue, decreased appetite, bleeding gums, shortness of breath, numbness or tingling in the arms or legs, weakness, loss of balance, confusion or poor memory. The only way to be sure you have a healthy level of vitamin B-12 is to ask your health professional to check your blood levels. A normal blood level is 200 to 900 picograms per milliliter, according to the Office of Dietary Supplements.
Sources
In addition to supplements, vitamin B-12 is obtained from animal food sources such as fish, meat, poultry, eggs and milk. According to the USDA Nutrient Database, the foods with the highest sources of vitamin B-12 are clams, beef liver and sirloin, turkey giblets, trout, salmon, haddock, tuna and fortified cereals. If you ate one 3-oz. hamburger, you'd get about 40 percent of the daily value of vitamin B12, compared to 3-oz of beef liver that provide over 1,000 percent. One bowl of fortified ready-to-eat breakfast cereal may deliver anywhere from 30 to 100 percent.
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