Which statement best describes the primary function of vitamin B12 and which populations are at risk for deficiency?

• A. Important for calcium absorption and bone health.
• B. Helps in digestion of fats.
• C. Essential for red blood cell formation and nerve function; at risk include older adults, vegans/vegetarians, and those with malabsorption.
• D. Maintains immune function.

Answer: (C)

Vitamin B12’s main role is in forming red blood cells and maintaining nerve function. It’s essential for DNA synthesis in bone marrow, which supports healthy, properly sized red blood cells, and it helps keep the myelin sheath around nerves intact, ensuring smooth nerve signaling. When B12 is deficient, red blood cells can’t develop normally, leading to megaloblastic anemia, and nerves can become damaged, causing tingling, numbness, and balance problems. Populations at risk for deficiency include older adults, who often have reduced stomach acid or conditions that limit absorption; vegans or vegetarians, who may not get enough B12 because it is primarily found in animal products unless fortified foods are used; and people with malabsorption issues such as pernicious anemia, Crohn’s disease, celiac disease, pancreas problems, or those who have had certain intestinal surgeries. Some medications, like certain acid-reducing drugs or metformin, can also impair absorption. Others choices point to roles better explained by other nutrients (for example, calcium and bone health relate to vitamin D and minerals; fat digestion involves bile and lipases; immune function is supported by several nutrients but isn’t the primary hallmark of B12).