Which of the following food substances will have little or no calorific value?

Step 1: Analyze the question The question asks which food substance gives little or no energy. Calorific value is the amount of energy released when a food substance is completely oxidised (burned) in the body.

Step 2: Explain the concept Energy values of the main food classes:

• Carbohydrates: about 17 kJ/g (≈ 4 kcal/g)
• Proteins: about 17 kJ/g (≈ 4 kcal/g)
• Lipids (fats and oils): about 37-39 kJ/g (≈ 9 kcal/g), the highest of all
• Water: 0 kJ/g. It is an inorganic substance and cannot be oxidised to release energy.
• Mineral salts and vitamins also provide no energy.

Step 3: Solution

• A. Proteins can be oxidised for energy, so they have calorific value.
• B. Carbohydrates are the body's main energy source, so they have high calorific value.
• C. Lipids give the most energy per gram, so they have very high calorific value.
• D. Water is not oxidised in respiration and releases no energy, so it has little or no calorific value.

Step 4: Answer The correct option is D. Water.

Step 5: Exam tip Remember that only the three organic nutrients (carbohydrates, proteins, lipids) supply energy. Water, mineral salts and vitamins do not. If a question asks about "no calorific value", look for one of those three. Also remember the order of energy content: lipids > carbohydrates ≈ proteins.