Epidemiology

The Framingham Offspring Study found up to 39% of US adults at risk for vitamin B12 deficiency (defined as serum vitamin B12 <350 picograms/mL).[10] Prevalence increases with advancing age, and ranges from 5% to 35% in older people depending on the population studied and the methods of diagnosis.[11][12][13][14][15][16][17]

In the US and the UK, the prevalence of vitamin B12 deficiency is approximately 6% in persons younger than 60 years, and nearly 20% in those older than 60 years.[18] Marginal vitamin B12 levels are found in approximately 20% of people in the US and UK.[19] Studies in other world regions including Scandinavia and the Middle East have found evidence of low serum vitamin B12 (<200 picograms/mL) in 25% to 70% of the studied population.​[20][21][22][23][24]

The prevalence of vitamin B12 deficiency is expected to rise with the increasing popularity of veganism and vegetarianism. The exact prevalence of deficiency among vegans and strict vegetarians is difficult to estimate due to study method heterogeneity; however, it may range from as low as 11% to as high as 90% depending on age.[25][26]

Rising numbers of gastric bypass procedures have led to an increase in vitamin B12 deficiency. Roux-en-Y gastric bypass surgery may cause deficiency in up to half of patients in the initial postoperative years due to inadequate absorption.[27][28]

Vitamin B12 deficiency may be seen in 20% to 30% of women during pregnancy, and is particularly common if the woman is vegetarian or vegan.[11][29]​ One systematic review found that levels of vitamin B12 decrease from the first to the third trimester.[30]

Use of this content is subject to our disclaimer