A rarer but severe cause of vitamin B-12 deficiency is pernicious anemia which occurs among people who cannot absorb vitamin B-12 because their bodies do not make a substance called intrinsic factor which is needed to absorb vitamin B-12. Unfortunately, vitamin B-12 is also a popular topic for deceptive treatments and questionable products (sublingual sprays, injections, nose drops) to counteract tiredness/fatigue without proper evidence of deficiency.
Older adults -- Many older adults do not have enough hydrochloric acid in their stomach to absorb the complex vitamin B-12 molecules that are naturally present in animal foods such as meats and dairy products. Fortified foods and dietary supplements contain a form of vitamin B-12 that is more easily absorbed. That is why the Dietary Guidelines for Americans recommends that people 50 and older “consume foods fortified with vitamin B12, such as fortified cereals, or dietary supplements.”
Vegetarians – The risk of vitamin B-12 deficiency among vegetarians, especially strict vegetarians or vegans who eat no animal foods, has been a source of controversy and confusion. The Academy of Nutrition and Dietetics (formerly American Dietetic Association) position statement on vegetarian diets recommends that vegans consume fortified foods or supplements because “no unfortified plant food contains any significant amount of active vitamin B-12.” A new review article summarizes published studies on this subject and reports that vegetarians of all ages are at increased risk of B-12 depletion or deficiency and recommends that vegetarians “take preventive measures to ensure adequate intake of this vitamin.”
Pawlak R, Parrott SJ, Raj S, Cullum-Dugan D, Lucus D. How prevalent is vitamin B12 deficiency among vegetarians? Nutrition Reviews. 71(2):110–117.
American Dietetic Association. Vegetarian Diets. J Amer Diet Assoc. 109(7):1266-1282.
Dietary Guidelines for Americans, 2010. Chapter 4 Foods and Nutrients to Increase. http://www.cnpp.usda.gov/Publications/DietaryGuidelines/2010/PolicyDoc/Chapter4.pdf
(pages 34 and 42).
By Susan Nitzke, UW-Extension Nutrition Specialist and UW-Madison Professor Emeritus