1. 1 Lecture 4 Ch. 5 Lipids

2. 2 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

3. 3 Fatty Acids Fig. 5-2, common to most lipids –long chains of carbon (C) and hydrogen (H) linked together –large variety of fatty acids –most fats are a mixture of fatty acids fig 5-3 Saturated all carbons full of Hydrogen animal fats, solid at room temp. Unsaturated –missing some H, has double bonds between some carbon atoms –Monounsaturated - one double bond –Polyunsaturated - two or more double bonds The location of the first double bond also names the type of unsaturated fatty acid –Omega-3(alpha linoleic acid-C18:3  3) –Omega-6 (linoleic acid -C18:2  6)

4. 4 Triglycerides Main form of fats in body Fig 5-1 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

5. 5 Other Fats Phospholipids (lecithins) –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 –Table 5.1 - cholesterol content in foods

6. 6 High Fat Foods Fig 5-5 Salad oils, butter, margarine, mayonnaise - close to 100% of calories from fat Avocados, bologna, bacon, cheese, peanut butter - about 80% of calories from fat Animal fats –very high in saturated fat –only source of cholesterol tropical oils –higher in saturated fats –Coconut and palm oil Reduced fat foods vary - many have same caloric value as original

7. 7 Fat Replacements Five types of replacements currently available to manufacturers Water Starch - binds water to form gel - feels a bit like fat in the mouth Gum Fiber - thickener, replaces bulk of food lost when fat removed Protein derived - microscopic globules - fees like fat Engineered fats - olestra (olean) –Chemical bond of FFA and surcose –Can not be digested by our enzymes or the bacteria in our GI –Binds fat soluble vitamins (ADEK) - added by manufacturers to compensate Replacements not having much impact –Not used in most high fat foods –Many will increase servings of low cal options

8. 8 Fat Digestion Initiated in stomach, primarily in small intestine - fig 5-7 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 binds and eliminates some bile, may reduce cholesterol

9. 9 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 - fig 5-8

10. 10 Fats in the Blood Fat and water do not mix Fat must be associated with lipoproteins to circulate in the blood TG broken down into FA and glycerol by enzymes (lipoprotein lipase) on wall of blood vessels –Fatty Acids absorbed into muscle and adipose cells –burned as fuel or reforms TG for storage

11. 11 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 with delivery of fat, forming LDL (low density lipoprotein) which is mainly cholesterol

12. 12 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), this fat then builds up on the inner walls of blood vessels, Over years of build up, this forms plaques which lead to atherosclerosis antioxidants - carotenoids, vit C and E –donate electrons reducing damage of oxidizing compounds

13. 13 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

14. 14 Cardiovascular Disease Fig 5-10 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 - heart attack disruption of plaque leads to clot formation and blockage plaque builds with cholesterol, protein, smooth muscle and calcium

15. 15 Risk Factors for CVD High cholesterol - over 200mg/dl –(dl = 100ml) high LDL - 130 - 160 mg/dl low HDL (high density lipoprotein) –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

16. 16 What you can do to reduce risk Diet changes for LDL –reduce sat fats and cholesterol –inc monounsaturated fats –inc dietary fiber (soluble) Blood triglycerides –do not overeat, limit alcohol and sugar –spread out meals Raise HDL –increase activity level –Reduce BP and TG

17. 17 Functions of Lipids Very diverse functions only some required in diet Essential Fatty Acids –humans can not make these –Important for body structures, immune system and vision, form cell membranes and hormone-like compounds Required in diet –Omega 3 - alpha linolenic acid –Omega 6 - linoleic acid –1 tbls of veg oil per day –fish twice a week (DHA -  3) –Soybean oil, canola oil, flax seed oil(keep in fridge) Moderation

18. 18 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) Texture and flavor

19. 19 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)

20. 20 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 –creates trans-fatty acids (fig 5.13) raises blood cholesterol and LDL avoid deep fried foods, non-dairy creamers, veg. Shortening FDA now requires labeling for trans fatty acid content in USA

21. 21 Recommendations No RDA, 4 % of calories from plant oils and eat fish twice a week upper limit of 30 % of caloric intake 10 : 10 : 10 (sat, mono, poly) Table 5-8- recommendations –polyunsaturates - LDL oxidation –reducing sat fats - clears LDL Max recommendations easily reached - fries - 30g of fat (mostly trans) recommendations do not apply to children under 2 years