Lecture 4 Ch. 5 Lipids

Lipids Overview Variety of compounds that do not dissolve in water Fats - solid at room temperature saturated fats - animal Oils - liquid at room temp. unsaturated fats - plants Triglycerides - storage form Phospholipids - polar and non-polar, form cell membranes Lipoproteins - carriers for fats in blood

Fatty Acids Fig. 5-1, common to most lipids long chains of carbon (C) and hydrogen (H) linked together large variety of fatty acids most fats are a mixture Saturated all carbons full of Hydrogen animal fats, solid at room temp. Unsaturated missing some H, has double bonds many d. bonds, polyunsaturated

Triglycerides Main form of fats in body 3 carbon glycerol with three fatty acids attached diglyceride - two F acids monoglyceride - one F acid fats become mono before absorption into SI, then reform triglycerides

Other Fats Phospholipids (lecithin) Sterols built on glycerol within body FA is replaced by phosphorous and nitrogen compounds becomes bipolar - can interact with fat and water - emulsification component of cell membranes Sterols multi ringed structure cholesterol - made in liver forms hormones, bile, cell membranes

High Fat Foods Salad oils, butter, margarine, mayonnaise Avocados, bologna, bacon, cheese, peanut butter Animal fats very high in saturated fat only source of cholesterol tropical oils higher in saturated fats Fat reduction not calorie reduction

Functions of Lipids Very diverse functions only some required in diet Essential Fatty Acids - humans can not make these Omega 3 - alpha linolenic acid Omega 6 - linoleic acid 1 tbls of veg oil, fish twice a week Moderation

Other roles of Lipids Energy storage - Adipose tissue very high density, limitless, low water content (light) energy - rest and light exercise 50% insulation - subcutaneous transport of vitamins - ADEK Satiety - needed for feeling of fullness (calorie reduced diet)

Other roles of Lipids Phospholipids - required in many components of body cells can be manufactured in body emulsifiers (lecithins) allow water and fat to mix, due to both water and fat soluble ends Cholesterol -components of hormones - estrogen, testosterone, vitamin D bile acids - fat digestion manufactured in liver - 100mg intake 200-300 mg (1/2 absorbed)

Hydrogenation For some baking, solid fat is more appropriate Polyunsaturated vegetable oils require hydrogenation to become more solid (similar to saturation) addition of hydrogen to double bonds also creates trans-fatty acids raises blood cholesterol (LDL) avoid deep fried foods, non-dairy creamers, veg. Shortening

Recommendations No RDA, 4 % of calories from plant oils and fish twice a week upper limit of 30 % of caloric intake 10 : 10 : 10 Table 5-2 polyunsaturated - LDL oxidation reducing saturated - clears LDL recommendations easily reached - fires - 30g of fat (mostly trans) Fig 5-4 recommendations do not apply to children under 2 years

Fat Digestion Initiated in stomach, primarily in small intestine TG broken into mono and di bile aids in emulsification formation of small micelle improves digestion and absorption by increasing surface area Enterohepatic circulation 98 % of bile re-circulated soluble fiber

Fat Absorption Passively absorbed into SI cells short chain FA (< 12) into portal circulation long chain (>14) into lymph circulation bind with cholesterol, phospholipids and protein coat to make lipoproteins

Fats in the Blood Must be lipoproteins to float in blood TG broken down into FA and glycerol by enzymes on wall of blood vessels absorbed into muscle and adipose cells burned or reform TG

Transport of Fats Liver produces fat and cholesterol from dietary intake coats cholesterol and TG in protein and phospholipids VLDL - very low density lipoprotein circulate and TG are broken down and absorbed by cells density increases, forming LDL which is mainly cholesterol

Low Density Lipoprotein LDL absorbed by liver and broken down to make bile ... process is inhibited by high saturated fat and cholesterol in diet If LDL is not taken up by liver, scavenger cells will oxidize fat (take an electron), fat builds up on inner walls of blood vessels, form plaques which lead to atherosclerosis antioxidant - donates electrons - fruits and veg - reduce damage of oxidizing compounds

High Density Lipoprotein High protein content (increases density) picks up cholesterol in blood stream transport back to liver, may prevent oxidation of LDL good versus bad cholesterol is dependant on carrier HDL versus LDL

Cardiovascular Disease Major killer in America symptoms develop slowly over many years - beginning in childhood associated with inadequate circulation to heart or brain (stroke) myocardial infarction - death of part of the heart fig 5-2 disruption of plaque leads to clot formation and blockage plaque builds with cholesterol, protein, smooth muscle and calcium

Risk Factors High cholesterol - over 200mg/dl (dl = 100ml) high LDL - 130 - 160 mg/dl low HDL - under 35 mg/dl Age - men over 45 women over 55 family history smoking High blood pressure diabetes lack of physical activity and obesity several factors compound risk

What you can do Diet changes for LDL Blood triglycerides Raise HDL reduce sat fats and cholesterol inc mono and polyunsaturated inc dietary fiber (soluble) Blood triglycerides do not overeat, limit alcohol and sugar, spread out meals Raise HDL increase activity BP, TG,