Which of the following is NOT one of the six classes of nutrients?

• A. Vitamins
• B. Lipids
• C. Probiotics
• D. Proteins

Answer: (C)

The six nutrient classes cover what the body uses for energy, growth, and all its functions: carbohydrates for energy, proteins for tissues and enzymes, lipids (fats) for energy and cell function, vitamins to regulate metabolism, minerals for structure and regulation, and water for hydration and biochemical reactions. Probiotics, while they can support digestion and gut health, are live microorganisms and not a standard nutrient category. They don't fit into the six classes the body relies on for energy and building blocks, so they are the one that does not belong.