What is the primary role of B vitamins?

B vitamins play a critical role in energy metabolism primarily by acting as coenzymes in various metabolic pathways. They help convert carbohydrates, fats, and proteins into energy, which is essential for the functioning of all cells in the body. This energizing function is particularly significant during physical activity and exercise, where energy demands are heightened.

Additionally, B vitamins are important for maintaining healthy skin and promoting the proper function of the nervous system. For example, B2 (riboflavin) and B3 (niacin) contribute to skin health, while B12 (cobalamin) is vital for neurological function and red blood cell formation. This dual role in energy metabolism and skin health defines their primary function classically recognized in nutrition science.

The other options refer to functions not primarily associated with B vitamins. Fat storage and digestion are primarily influenced by other nutrients and hormones. Bone strength typically relies more on vitamins such as D and minerals like calcium. Immune system regulation also involves various nutrients, including vitamins A, C, and D, rather than being predominantly linked to B vitamins. Therefore, the emphasis on energy metabolism and skin health solidifies the understanding of B vitamins' primary role within the human body.