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Agenda

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  1. Agenda • A cool app • Lecture on Lipids • Hand back/go over the test • Lecture outline • Hidden Fat on Food Labels • Hydrogenation • Lipid Digestion and Absorption • Fatty Acid Function • Cardiovascular Disease

  2. Lecture 8: Lipids Groundhog Day Feb 2, 2012 Will Brown

  3. A Cool App • http://www.fooducate.com/ • Allows you to scan the bar code of a product • Gives it a grade: A-F • Allows you to find better alternatives in the same product category • Also makes shopping lists based on the products you have scanned • Fair warning: it will turn a 30 min shopping trip into a hour one

  4. Lipid: A Quick Review of Last Time • Lipids are hydrophobic • 3 main types in the body; Triglycerides, Phospholipids, and Cholesterol • Fatty acids are long chains of carbon • Saturated • Unsaturated – mono or polyunsaturated • Unsaturated named by where the first double bond is located; ie: omega-3 has first double bond on the 3rd carbon from methyl end • Trans fat is unsaturated but acts like a saturated

  5. Hidden Fat on Food Labels

  6. Hidden Fat on Food Labels • No Cholesterol! Except it is not made of animal product • Calories: 70 kcal • Calories from Fat: 25 kcal • 70/25 * 100 = 35.7% of calories come from fat

  7. Hidden Fats on Food Labels • Ingredients on labels are listed in order by weight • Second thing on the list is Soybean Oil with TBHQ • Third thing is sugar The first three ingredients are: processed carbs, processed fat, and processed carbs

  8. What about the “Reduced Fat” version? • Same amount of Calories: 70 • Reduced Fat from 3g to 2g • Calories from fat down from 25 to 20 • 20/70 * 100 = 28.5% • That is only 7.2% less than the full fat version

  9. What are you really gaining by reducing the fat?

  10. What else the label isn’t telling you. • Fat free does not mean free of all fat. • FDA definition of fat free is less than 0.5g of fat per serving • Make a serving small enough and anything could be considered “Fat Free” • Same goes for Saturated Fat Free - <0.5g/serving • Low Fat – <3g/serving unless serving is smaller than 30g or 2 Tbsp; then it is <3g/50g of food • 2% milk can no longer be labeled as “Low Fat”

  11. What else the label isn’t telling you. • Reduced or Less fat and saturated fat: <25% from reference food • Cholesterol free: >2mg and 2g sat fat/serving • Low Cholesterol: <20mg and <2g of sat fat/serving • Reduced Cholesterol: at least 25% less than reference food

  12. Things to remember about fat choices • Check the labels: Reduced fat or fat free does not mean reduced calorie • To really change fat intake you might have to switch to a different food intake – switch to leaner cuts of meat, increase plant based fats and proteins • Fat free does not mean there is no fat

  13. A quick word on “Hydrogenation” • Process to increase the number of hydrogens on a fatty acid chain • Bubble hydrogen gas through vegetable oil under pressure • Results in high number of trans fat • Considered bad for your health; FDA recommends minimal intake • Required to be listed on food labels but sometimes difficult to find • Check the label for “partially hydrogenated” or “hydrogenated” oils

  14. Lipid Digestion • Stomach – little digestion of fat but not much; Lipase activity • Liver – produces bile; helps to emulsify and breakdown fat • Pancreas – produces more lipase and other enzymes • Small Intestine – Primary digestion site; absorption of long chain fatty acids into lymph; short chain directly into circulation • Large Intestine – less than 5% excreted

  15. Lipid Absorption

  16. Lipoproteins are vehicles for fat • Because oil and water don’t mix; fat must be carried in the blood by transport molecules called lipoprotein • 4 different types

  17. Chylomicrons • Derived from the intestinal cells • Carry dietary fat • Composed of inner droplet of fat surrounded by a single layer of phospholipid • Also contain embedded protein • Contains lipoprotein lipase that breaks down triglycerides inside • Fatty acids diffuse out and used by other tissues; muscle • Glycerol and chylomicron remnants recycled by liver Xvasquez, 2008

  18. Lipoproteins Lipids collected or produced by liver Cholesterol from dying cells or LP metabolism Fats from a meal Package derived from intestine Package derived from iLiver HDL picks up and transfers to other LP or liver VLDL deliver FA to cells Chylomicron delivers FA to cells LDL derived from VLDL as FA are removed LDL deliver cholesterol to cells

  19. The Good, The Bad, and The Ugly • The Good - HDL • Not actually cholesterol • Carries cholesterol back to liver which clears the blood of extra cholesterol • The Bad – LDL • LDL taken up by various receptors on cell surface • If extra LDL is present it is taken up by scavenger cells lining the blood vessels • The Ugly – Atherosclerosis • Causes hardening and narrowing of vessel wall • Can lead to cardiovascular disease

  20. Fatty Acid Function • Only certain polyunsaturated fats are essential in the diet – we lack the enzymes to make them • Linoleic acid – omega-6 fatty acid • Alpha-linoleic acid – omega-3 fatty acid • Omega-3 are shown to ↓ blood clotting; omega-6 ↑ blood clotting • Fatty fish high in good omega-3 so reduce the chance for stoke; however to much of a good thing = hemmorhagic stroke

  21. Roles for Fatty Acids • Help with certain vitamin absorption • Energy • Stored fat is higher in calories than carbohydrates and take up less space and weight • Adipose cells can grow up to 50 times • Triglycerides are stable compounds • Triglycerides don’t store water with them whereas carbs do • Primary source of energy during rest and light activity • Insulation and protection • Thin layer of subcutaneous fat • Layer of adipose tissue that surrounds various organs for protection

  22. Phospholipid Functions • Many types are present in the body • Form plasma and nuclear membranes in every cell • In food, acts as emulsifiers • Remember the eggs in mayo? • Also act as emulsifiers in small intestine to aid in digestion

  23. Cholesterol • Forms backbone structure for hormones, such as estrogen and testosterone, and vitamin-D • Forms part of the bile componants • Embedded in plasma membrane to help keep fluidity in cells • ~875mg of cholesterol is needed by the body • 400 mg goes to bile acid • 50 mg for hormones • Increased consumption can lead to increased LDL and increased risk of cardiovascular disease

  24. How much fat should you eat? • There is no RDA for adults • Remember, you can make all that you need and plants supply what is necessary in the diet • There are guidelines • Should be limited to 20-35% of total calories; 44-78 g for a 2000 kcal diet • AHA focuses on the ratio of types of cholesterol in the blood • ≤7% total calories from sat fat and ≤ 1% from trans fat • Maximum dietary cholesterol is 300mg/day

  25. Take home message for fat consumption • Limit the amount of Saturated fat • Remove as much trans fat from the diet as possible • Limit cholesterol to 300 mg/ day • Increase omega-3 and omega-6 fatty acids • Can be done with a fish oil pill • Or, eat more fish • Do not exceed 30% total calories from fat

  26. Why worry about Cardiovascular disease? • The major killer in north America • ~500,000 people die annually from coronary heart disease – 60% more than cancer! • When expanded to all cardiovascular disease • 1 million die annually • 1.5 million suffer heart attack • Men at a 2:1 ration to women, but eventually women catch up later in life • Kills twice as many women as cancer • Considered one of the most preventable diseases

  27. Progression • Plaque formation can begin early in childhood • Autopsies have shown plaques in people as young as 20 • As the plaque grows it can lead to a narrowing of the vessel causing reduced blood flow • Low blood flow results in irregular heart beat and eventually to myocardial infarction (heart attack) • In the brain it leads to cerebrovascular accident (Stroke).

  28. Atherosclerosis • Most likely begins as part of the normal healing process • Blood vessels can suffer damage • Blood clot forms to help repair • In plaque areas the clot does not break down as fast • In some cases it does not go away at all • Chronic inflammation is considered a contributing factor

  29. Plaque Formation • Initial damage occurs • LDL taken up by scavenger cells – oxidized LDL is preferentially taken up • This is why all the buzz surrounds antioxidants • Primary sources are fruits and vegetable – not only provide antioxidants but also less fat • As plaque grows, causes narrowing and hardening – reduced elasticity further damages vessel • Also, not just restricted blood flow causes problems – plaque pieces can break off and float into other parts of the body; can cause thrombosis

  30. Risk Factors for Heart Disease • Total blood cholesterol >200mg/dL of blood • Especially high when over 240 mg/dL and LDL exceeds 130 mg/dL • Smoking • Increases risk of CV event by 20% • Hypertension – Systolic pressure over 139 ml of mercury and diastolic pressure over 89. • Diabetes – pretty much guarantees a CV event • Remember insulin ↑ cholesterol synthesis in the liver, thus elevating LDL

  31. How to mitigate risk • QUIT SMOKING • Overhaul diet and lifestyle • Switch to low-fat diet • Increase exercise • Medications for more aggressive treatment • Statins – reduce liver production of cholesterol • ~$1600 annual • Bile binders/inhibitors – block the emulsifying effects of bile reducing the cholesterol consumed • Triglyceride production inhibitors – aim to reduce triglyceride production in the liver • Overall goal of therapy is to get blood LDL < 70mg/dL

  32. The Test!

  33. The Test! • Mean = 80 • Median = 78 • Mode = none • Distribution

  34. Extra Credit Opportunity • Do lab 7 at home • I will provide you with necessary lab consumables • You do the lab and answer the questions at the end • Any points that you get I will apply directly to your test score