People following plant-based diets can obtain adequate nutrition, but certain groups are at increased risk of vitamin B12 deficiency because dietary sources and absorption vary. Winston J. Craig of Loma Linda University emphasizes that people who avoid all animal products without using reliable fortified foods or supplements are particularly vulnerable. The Office of Dietary Supplements, National Institutes of Health notes that the risk rises further when diet is combined with physiologic or medical factors that reduce B12 absorption.
Causes and who is most vulnerable
The primary cause is the absence of bioavailable vitamin B12, which is naturally found in animal-derived foods. Strict vegans, including adults who avoid all dairy and eggs and those who consume mainly unfortified plant foods, are at heightened risk. Infants breastfed by mothers who follow unfortified vegan diets are especially susceptible because newborn stores depend on maternal status. Pregnant and breastfeeding women need dependable B12 intake to protect fetal and infant neurodevelopment. Older adults face increased risk because age-related decline in stomach acid and intrinsic factor can impair absorption, making dietary intake alone less reliable. People with gastrointestinal conditions such as pernicious anemia, atrophic gastritis, Crohn’s disease, or those who have had bariatric surgery also often cannot absorb B12 efficiently, and medications such as metformin or proton pump inhibitors can further reduce absorption. Socioeconomic and geographic factors matter: access to fortified foods or supplements varies between countries and communities, and cultural dietary patterns that favor whole, unfortified traditional staples can create additional risk.
Consequences and practical considerations
Untreated vitamin B12 deficiency can cause megaloblastic anemia and progressive neurological damage, which in infants and young children may lead to long-term developmental impairment. The Office of Dietary Supplements, National Institutes of Health underlines that neurological consequences can occur even without obvious anemia. Winston J. Craig of Loma Linda University recommends that those on strict plant-based diets use reliable sources such as fortified foods or B12 supplements, and that pregnant or breastfeeding individuals and older adults monitor status with health professionals. Cultural respect for dietary choices and resource-sensitive approaches are important: public health strategies that increase availability of fortified foods and culturally appropriate guidance can reduce risk without undermining the environmental or ethical motivations that lead many to choose plant-based diets.