Which vitamin may be lacking in a vegan diet because it does not naturally occur in plants?

Vitamin B12 is essential for the body's proper functioning, particularly for nerve function and the production of red blood cells. This vitamin is unique among the B vitamins because it is primarily found in animal products such as meat, dairy, and eggs. While fortified foods and supplements can provide adequate amounts of B12 for those following a vegan diet, it is not naturally present in plant-based foods. Therefore, individuals adhering to a vegan diet may be at risk of vitamin B12 deficiency unless they take specific dietary measures to include it.

Vitamins such as A, C, and D can be obtained from various plant sources or through fortified foods. For instance, vitamin A can be found in plant foods in the form of carotenoids, vitamin C is abundant in fruits and vegetables, and vitamin D can be synthesized in the skin from sunlight or obtained through fortified foods. Thus, the lack of naturally occurring sources of vitamin B12 in plant-based diets emphasizes its significance and potential deficiency risk for vegans.