Principles of Nutrition
- Digestion – process by which food substances are changed into forms that can be absorbed through cell membranes
- Absorption – the taking in of substance by cells or membranes
- Metabolism – sum of all physical and chemical processes by which a living organism is formed and maintained and by which energy is made available
- Storage – some nutrients are stored when not used to provide energy; e.g. carbohydrates are stored either as glycogen or as fat
- Elimination – process of discarding unnecessary substances through evaporation, excretion
Nutrients
1. Carbohydrates – the primary sources are plant foods
Types of Carbohydrates
- Simple (sugars) such as glucose, galactose, and fructose
- 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.
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- 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.
- Water-soluble vitamins include C and B-complex vitamins
- 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
- Macronutrients – calcium, phosphate, sodium, potassium, chloride, magnesium and sulfur
- 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