Which of the following is NOT a macronutrient?

Vitamins are classified as micronutrients, not macronutrients. While macronutrients include fats, carbohydrates, and protein, which are essential for energy production and overall bodily function, micronutrients like vitamins and minerals are required in smaller amounts for various physiological functions, including immune response and bone health.

Macronutrients serve as the primary sources of energy and are crucial for growth, metabolism, and other bodily functions. Fats provide energy and support cell growth, carbohydrates are the body's main energy source, and protein is essential for tissue repair and growth. In contrast, vitamins play supportive roles, aiding in biochemical reactions and helping to maintain good health, but they do not provide energy like macronutrients. Therefore, identifying vitamins as the option that is NOT a macronutrient is correct within the context of nutrition classification.