Final answer:
Proteins and carbohydrates both provide about 4 Calories per gram, which are the lowest caloric values among the macronutrients listed, with fats providing 9 Calories per gram.
Step-by-step explanation:
When comparing which macronutrient has the lowest caloric value, it's essential to look at the calories provided per gram by each. Proteins offer about 4 Calories per gram, a number matched by carbohydrates. However, fats stand out by providing roughly 9 Calories per gram. Conversely, vitamins do not provide energy, as they are micronutrients essential for other body functions but not caloric content.
Therefore, proteins and carbohydrates tie for having the lowest caloric value amongst the choices given, both yielding 4 Calories per gram.