Final answer:
The correct answer is Vitamin B3, which is essential for metabolism and found in a variety of foods such as beef, eggs, milk, legumes, and enriched grains.
Step-by-step explanation:
The nutrient being described in the question processes carbohydrates, proteins, and fats, and is found in beef, eggs, milk, legumes, and enriched grain products. This describes Vitamin B3, also known as niacin. Niacin is involved in many metabolic processes within the body and is essential for the conversion of food into energy.
Food sources of niacin include cereals, nuts, oil seeds, eggs, liver, wheat grain, legumes, rice polishing, milk, meat, fish, and certain vegetables like potatoes. Adequate intake of niacin is important, as it plays a crucial role in the functioning of the digestive system, skin, and nerves, and in maintaining a healthy appetite.