Which B vitamin is essential for carbohydrate metabolism and is found in whole grains and cereals?

Thiamin, also known as Vitamin B1, plays a crucial role in carbohydrate metabolism. It acts as a coenzyme in the conversion of carbohydrates into energy, helping the body utilize glucose effectively. Thiamin is essential for the proper functioning of enzymes involved in this metabolic pathway. The presence of thiamin in whole grains and cereals makes these foods important dietary sources of this vitamin, contributing to overall energy production and metabolic health.

While the other B vitamins listed are also important for various metabolic processes, they have different specific roles that do not directly focus on carbohydrate metabolism in the same way as thiamin. For example, riboflavin is more involved in the metabolism of fats and proteins, niacin plays a key role in the conversion of carbohydrates and fats into energy but is not as directly tied to carbohydrate metabolism specifically, and pantothenic acid is involved in the synthesis of coenzyme A, which is crucial for various metabolic functions but does not specifically address carbohydrate metabolism. Thus, thiamin's specific role in carbohydrate metabolism distinctly positions it as the correct answer.