Which vitamin is known for its role in energy metabolism?

B-complex vitamins, particularly B1 (thiamine), B2 (riboflavin), and B3 (niacin), play a crucial role in energy metabolism. These vitamins are essential co-factors in several enzymatic reactions that convert carbohydrates, fats, and proteins into energy.

Thiamine is involved in the decarboxylation of pyruvate, linking glycolysis to the citric acid cycle, while riboflavin is a component of coenzymes that assist in the oxidation-reduction reactions critical to energy production. Niacin is a precursor for NAD and NADP, which are key molecules involved in catabolic reactions that generate ATP. Without sufficient amounts of these B-vitamins, the body would struggle to produce the energy required for various cellular functions and overall metabolism.

Other options, such as vitamin A, vitamin E, and vitamin K, have important roles in vision, antioxidant protection, and blood clotting, respectively, but they do not directly participate in the metabolic pathways that produce energy.