Biology

• Carbohydrates- main source of energy (57% engery intake)
• Proteins- essential for growth and repair of muscles and other body tissues (13% emergy intake)
• Fats- essential as a source of energy and also important in cell membranes, waterproofing, absorbtion of fat-soluble vitamins, as well as many other roles (30% engery intake)
• Vitamins- these play important roles in the chemical processes taking place inside cells. Some are water-soluble and some are fat-soluble
• Minerals- these are the inorganic elements occuring in the body that are essential to normal functions
• Water- this is essential for the body to funtion as 60% of the human body is made up of water. Its used in transporting substances around the body
• Fibre/ Roughage- this is the indigestable part of the food which is essential for healthy functioning of the digestive system

HDL's

• Made up of unsaturated fats, cholesterol, and proteins
• Tend to carry cholesterol from the body tissues back to the liver. in the liver it contains receptor sites that allow the HDL's to bind to their cell surface membranes
• In the liver the cholesterol is used in cell metabolism (make bile) or is broken down
• High levels of HDL's = reduced blood cholesteol levels

They reduce the fatty deposits in the artery walls by atherosclerosis and may even help in the removal of them. As HDL's are unsaturated they are said to be benefical to health

LDL's

• made from saturated fats, cholesterol and proteins
• Carry cholesterol from the liver to the tissues. The tissues have cell receptors that allow the LDL's to bind to the cell surface membranes
• If to much cholersterol is consumed in the diet the concentration of LDL's in the blood will rise causing deposits in the artery walls

Different fats affect LDL receptors differently;

• Saturated fats- decrease activity of LDL's
• Polyunsaturated fats- increase LDL's activity
• Monounsaturated fats- remove LDL's from blood