Vitamin B12 Intakes and Status
Most children and adults in the United States consume recommended amounts of vitamin B12, according to analyses of data from the 1988–1994 National Health and Nutrition Examination Survey (NHANES III) and the 1994–1996 Continuing Survey of Food Intakes by Individuals. Data from the 1999–2000 NHANES indicate that the median daily intake of vitamin B12 for the U.S. population is 3.4 mcg.
Some people—particularly older adults, those with pernicious anemia, and those with reduced levels of stomach acidity (hypochlorhydria or achlorhydria) or intestinal disorders—have difficulty absorbing vitamin B12 from food and, in some cases, oral supplements. As a result, vitamin B12 deficiency is common, affecting between 1.5% and 15% of the general population. In many of these cases, the cause of the vitamin B12 deficiency is unknown.
Evidence from the Framingham Offspring Study suggests that the prevalence of vitamin B12 deficiency in young adults might be greater than previously assumed. This study found that the percentage of participants in three age groups (26–49 years, 50–64 years, and 65 years and older) with deficient blood levels of vitamin B12 was similar. The study also found that individuals who took a supplement containing vitamin B12 or consumed fortified cereal more than four times per week were much less likely to have a vitamin B12 deficiency.
Individuals who have trouble absorbing vitamin B12 from foods, as well as vegetarians who consume no animal foods, might benefit from vitamin B12-fortified foods, oral vitamin B12 supplements, or vitamin B12 injections.