What is the primary role of B vitamins in relation to bodily functions?

B vitamins play a crucial role in the body's metabolic processes by acting as coenzymes in the conversion of food into energy. They are essential for breaking down macronutrients such as carbohydrates, fats, and proteins, enabling the body to utilize these nutrients effectively. This energy production is vital for numerous bodily functions, including those that support overall health and well-being.

While the other options highlight important health aspects, they are not the primary functions of B vitamins. For instance, supporting immune health and promoting healthy hair growth are influenced by various nutrients and factors, but they are not the principal role of B vitamins. Similarly, hormonal balance involves a complex interaction of multiple hormones and nutrients, rather than being solely reliant on B vitamins. Thus, the correct option underscores the fundamental biochemical role that B vitamins play in nutrient metabolism.