Dietary Lipids Sources of Essential Fatty Acids o Omega 6 fatty acids main dietary source is linoleic Most vegetable oils nut and seed oils o Omega 3 fatty acids main dietary source is alpha linolenic Soy oil flaxseed leafy green vegetables Fish have a longer chain omega 3 Associated with reduced heart disease Cis fatty acids have a bend in the carbon chain whereas trans fatty acids do not Vegetable oils are liquid at room temperature because they are high in unsaturated fatty acids The bent chains of these fatty acids prevent tight packing allowing the oil to flow The fat in margarine is solid at room temperature because the trans unsaturated bonds allow the fatty acids in the triglycerides to pack tightly together Phospholipids Oil to hydrophobic core Then hydrophobic portion of lecithin Then hydrophilic portion of lecithin Then 2 fatty acids o o Glycerol o o o Phosphorous containing molecule Properties hydrophobic and hydrophilic ends Functions Helps with fat absorption emulsifier Lecithin bile salts electrolytes bile Helps transport dietary fats in circulation Part of the cell membrane In food emulsifier mayonnaise salad dressing o Liver makes phospholipids so not essential Foods animal cell membranes egg yolks o Emulsification o Lecithin has a hydrophilic and a hydrophobic head o Oil water lecithin plus agitation bubbles of oil in water Sterols water around hydrophilic shell 4 carbon rings Found in food and made in body o o o Cholesterol is the most common dietary sterol only found in animals o High cholesterol increases CHD risk o Plant sterols can reduce CHD risk Cholesterol a sterol Functions o Bile salt precursor Cell membrane structure Hormones glucocorticoids Estrogen testosterone Vitamin D Cholesterol has a very similar structure to Vitamin D3 Sources animal products produced by animals Non essential in the diet Health issue raises LDL C cholesterol General goal 300 mg day 3 oz meat 100mg Essential fatty acid deficiency Lipid digestion and absorption o Essential fatty acids are important for growth skin integrity fertility and the structure and function of cell membranes If adequate amounts of essential fatty acids are not consumed a deficiency can result Symptoms include dry scaly skin liver abnormalities poor wound healing growth failure in infants and impaired hearing and vision o o o A small amount of digestion occurs in the stomach o The liver produces bile which is released into the small intestine to aid in the digestion and absorption of fat o The pancreas produces the enzyme pancreatic lipase which is also released into the small intestine to break down triglycerides into monoglycerides fatty acids and glycerol o o o Since fat absorption in the small intestine is efficient very little fat is normally lost in feces In the small intestine the products of fat digestion and bile acids form micelles which move close enough to the microvilli to allow lipids to diffuse into the mucosal cells Inside the mucosal cells fatty acids and monoglycerides are reassembled into triglycerides and incorporated into lipid transport particles which enter the lymph Enzymes in the digestive tract lipases break down triglyceride and release free fatty acids Lipase action o Mouth not much some in infants Stomach gastric lipase not much o Small intestine o CCK stimulates gall bladder to release bile and pancreatic lipase Lipases break TG into monoacylgyceride and two free fatty acids Enterohepatic Circulation of Bile o Bile made in the liver stored in the gall bladder emulsifies fat in small intestine allowing enzymes to hydrolyze it into smaller units that can be absorbed bile is either reabsorbed into the blood OR in the colon bile that has been trapped by viscous fibers is lost in feces o Greenish fluid containing Bile salts derived from cholesterol Phospholipids e g lecithin Cholesterol Bile pigments o Bile secretion stimulated by CCK Lipid absorption and transport Fatty acids don t mix well with water o o Bile emulsifier o Micelles formed Transport lipid digestion produces into enterocytes Reassembly of the lipid components into a chylomicron o In the enterocyte Short and medium chain fatty acids less than 14 carbon chain enter portal circulation Long chain fatty acids reassembled into TG Combined with cholesterol phospholipids and small protein You now have a lipoprotein called a chylomicron Chylomicrons enter the lymph then the bloodstream Overview of lipid digestion absorption and transport o Lipase from pancreas breaks down fat into fatty acids and monoglycerides o Monoglycerides and fatty acids are absorbed through villi via micelles and then re form into triglycerides o Triglycerides aggregate and are combined with cholesterol protein and phospholipids to form chylomicrons Lipids that are not soluble in water include long chain fatty acids cholesterol and fat soluble vitamins Lipoproteins Lipids in the blood circulation o Lipoproteins transport lipids and cholesterol in the blood o Chylomicrons o Very low density lipoproteins VLDL o Low density lipoproteins LDL CHD risk o High density lipoproteins HDL protective o Types of lipoproteins that transport dietary lipids Protein components adolipoprotiens involved in metabolism and final disposition of lipoprotein Intermediate density lipoprotein IDL less fatty acids than VLDLs deliver fatty acids made by liver o Very low density lipoproteins VLDL deliver fatty acids made by liver o o Low density lipoprotein LDL less fatty acids than IDLs deliver cholesterol o High density lipoprotein HDL pick up scavenge excess cholesterol from cells for delivery back to the liver o Chylomicron delivery of dietary fatty acids Cardiovascular disease CVD o Abnormal condition of the heart and blood vessels o Atherosclerosis narrowing and hardening of blood vessels that supply blood to the heart muscle brain and other parts of the body o Coronary heart disease CHD heart not receiving enough blood o Stroke brain not receiving enough blood Individual nutrients and food components o Factors that increase risk cholesterol saturated fat trans fat sodium excess sugar and excess energy o Factors that reduce risk polyunsaturated fat monosaturated fat fiber B vitamins antioxidants moderate alcohol o High blood pressure age gender blood lipid levels activity genetic background diet smoking overweight obesity Risk factors for heart disease Heart healthy diet Fiber 25 gm daily 10 25g soluble for cholesterol lowering o Nuts fruits and vegetables and whole