Nutritions - The Introduction Nutrients are substances obtained from outside for maintaining the living process, which occurred in the organisms. Nutrients, briefly classified as essential or non-essential. Essential nutrients are not constructed by our bodies, but obtained from food. Nutrition can also be grouped mainly into two categories, inorganic substances and organic substances. Properties list as follows: Inorganic substances Organic substances Natural, small and simple molecules Large and complex molecules Mostly without carbon (except carbon dioxide) Containing carbon, thus with higher chemical energy Naturally produced Produced by living things e.g. Water, minerals, salt, iron and carbon dioxide e.g. Carbohydrate, protein, fat and vitamins