An adult who is following a vegan diet, should take this vitamin as a supplement.

• A. Vitamin C
• B. Vitamin B12
• C. Vitamin D
• D. Vitamin A

Answer: (B)

Vitamin B12 is the nutrient vegans most need to supplement because it is not reliably found in plant-based foods. B12 comes from bacterial sources and is accumulated in animal tissues, so avoiding animal products makes dietary B12 intake unreliable unless you use fortified foods or a supplement. A deficiency can develop gradually and lead to fatigue, anemia, and neurological problems due to impaired nerve myelination. For this reason, adults on a vegan diet are advised to take a B12 supplement, commonly as cyanocobalamin or methylcobalamin, in a small daily dose or an appropriate weekly dose. Other vitamins may be a concern for some individuals, but B12 deficiency risk is the standout issue with a vegan diet because plant-based eating does not provide a dependable B12 source. Vitamin C is abundant in fruits and vegetables; vitamin D needs depend on sun exposure and may require supplementation in some people; and vitamin A can be obtained from plant carotenoids.