Which individuals are at risk for vitamin B12 deficiency, and what signs are typical?

• A. Regular meat eaters with excellent absorption; signs include improved energy
• B. Vegans, older adults with atrophic gastritis, and those with pernicious anemia; signs include fatigue, numbness/tingling, neuropathy, and cognitive changes
• C. Healthy adults with no risk factors; signs include none
• D. Infants exclusively breastfed; signs include iron overload

Answer: (B)

The concept being tested is who is at risk for vitamin B12 deficiency and what symptoms typically appear when it occurs. B12 deficiency tends to show up when intake is low or absorption is impaired, and it affects both red blood cell production and nerve function.

Vegan diets lack animal-derived B12, so individuals who avoid all animal products are at risk because plant foods don’t provide reliable B12. Older adults often have reduced stomach acid and loss of intrinsic factor with aging, or they develop atrophic gastritis, which impairs B12 absorption. Pernicious anemia is an autoimmune condition in which intrinsic factor is destroyed, making it difficult to absorb B12 from the gut. These groups are most likely to develop deficiency.

The hallmark signs reflect the dual impact on blood formation and the nervous system: fatigue from anemia, numbness or tingling in the hands and feet, neuropathy, and cognitive changes such as memory problems or changes in mood or thinking. This constellation of symptoms aligns with the impaired production of healthy red blood cells and the effect of B12 on myelin and nerve integrity.

Other options don’t fit because regular meat eating provides ample B12, so deficiency is unlikely and energy would not be expected to improve in that scenario. A healthy adult with no risk factors would not typically present with deficiency signs. Infants who are exclusively breastfed may be at risk if the mother is deficient, but iron overload is not a sign of B12 deficiency in infants.