What term describes substances in food necessary for body function?

The correct term that describes substances in food necessary for body function is nutrient. Nutrients are vital for various bodily processes, including growth, metabolism, and overall health. They can be categorized into macronutrients (such as carbohydrates, proteins, and fats) and micronutrients (such as vitamins and minerals), each playing specific roles in maintaining bodily functions.

While calories are a measure of energy derived from food, they do not describe the substances themselves. Enzymes are proteins that act as catalysts in biochemical reactions but are not substances that provide nutrition. Minerals are indeed a type of nutrient, but the broader term 'nutrient' includes all types of substances necessary for healthy body function, such as vitamins, carbohydrates, and proteins as well. Therefore, nutrient is the most encompassing and accurate term.