Iron deficiency is common in vegans: Vegans and vegetarians may be at risk for iron deficiency due to the limited sources of this nutrient in a plant-based diet. Combining biotin with iron in a supplement may help to address this issue. Biotin and iron have complementary roles in the body: Biotin plays a role in the metabolism of fats, carbohydrates, and proteins, while iron is essential for the production of red blood cells and the transport of oxygen throughout the body.