Principles of Nutrition

  1. Digestion – process by which food substances are changed into forms that can be absorbed through cell membranes
  2. Absorption – the taking in of substance by cells or membranes
  3. Metabolism – sum of all physical and chemical processes by which a living organism is formed and maintained and by which energy is made available
  4. Storage – some nutrients are stored when not used to provide energy; e.g. carbohydrates are stored either as glycogen or as fat
  5. Elimination – process of discarding unnecessary substances through evaporation, excretion

1. Carbohydrates – the primary sources are plant foods

Types of Carbohydrates

  1. Simple (sugars) such as glucose, galactose, and fructose
  2. Complex such as starches (which are polysaccharides) and fibers (supplies bulk or roughage to the diet)

2. Proteins – organic substances made up of amino acids

3. Lipids – organic substances that are insoluble in water but soluble in alcohol and ether.

    • Fatty acids – the basic structural units of all lipids and are either saturated (all the carbon atoms are filled with hydrogen) or unsaturated (could accommodate more hydrogen than it presently contains)
    • Food sources of lipids are animal products (milk, egg yolks and meat) and plants and plant products (seeds, nuts,oils)

4. Vitamins – organic compounds not manufactured in the body and needed in small quantities to catalyze metabolic processes.

  1. Water-soluble vitamins include C and B-complex vitamins
  2. Fat-soluble vitamins include A, D, E, and K and these can be stored in limited amounts in the body

5. Minerals – compounds that work with other nutrients in maintaining structure and function of the body

  1. Macronutrients – calcium, phosphate, sodium, potassium, chloride, magnesium and sulfur
  2. Micronutrients (trace elements) – iron, iodine, copper, zinc, manganese and fluoride The best sources are vegetables, legumes, milk and some meats

6. Water – the body’s most basic nutrient need; it serves as a medium for metabolic reactions within cells and a transporter fro nutrients, waste products and other substances