Which vitamin is most commonly deficient in vegan diets?

Vitamin B12 is the nutrient most commonly lacking in vegan diets because it is primarily found in animal products such as meat, dairy, and eggs. Vegans, who avoid all animal-based foods, may struggle to obtain sufficient amounts of this essential vitamin, which plays a crucial role in the production of red blood cells, DNA synthesis, and neurological function.

In contrast, while vitamin D, A, and C are important vitamins, they can often be sourced from plant foods or synthesized in the body. For instance, vitamin D can be obtained through fortified foods or sunlight exposure, vitamin A can be derived from plant sources in the form of provitamin A carotenoids (such as beta-carotene), and vitamin C is abundant in many fruits and vegetables. Thus, the distinct nature of vitamin B12 being exclusive to animal products makes it particularly vulnerable to deficiency in those following a vegan diet.