FSHN 220 Chapter 6-Lipids Pt 2

Part 2 of Lipids Slideshows

Fat Intake

• North America fat intake has doubled in the last century

• Omega 6 intakes are plentiful

• Omega 3 intakes are usually low: food sources, supplements, cautions

Fat Digestion Places

• Mouth: Lingual lipase

• Stomach: Gastric lipase

• Small Intestine:

  • CCK triggers bile

  • Bile emulsifies fat→ micelles are formed→ acted upon by pancreatic lipase and colipase

Fat Digestion in the Small Intestine

• Triglycerides are broken down into monoglycerides and free fatty acids

• Phospholipids are broken down into free fatty acids, glycerol, and phosphoric acid

• Cholesterol esters are broken down into cholesterol and free fatty acids

Fat Digestion Course- Mouth

Lingual lipase is secreted. Little or no fat is digested.

Fat Digestion Course- Stomach

Gastric lipase is secreted. Little fat is digested.

Fat Digestion Course- Liver

The liver produces bile, which is stored and released by the gallbladder into the common bile duct, which empties into the small intestine. Bile emulsifies fat.

Fat Digestion Course- Pancreas

The pancreas secretes pancreatic lipase, phospholipase, and cholesterol esterase into the common bile duct, which empties into the small intestine. Pancreatic lipase digests triglycerides. Phospholipase digests phospholipids. Cholesterol esterase digests cholesterol.

Fat Digestion Course- Small Intestine

Fat is digested and absorbed in the duodenum and jejunum. Bile is reabsorbed in the ileum.

Fat Digestion Course- Large Intestine

Less than 5% of fat passes through the large intestine and is excreted.

Fat Absorption

• Short- and medium-chain fatty acids are absorbed via the portal vein (to LIVER)

• Long chain fatty acids are re-esterified and enter the LYMPHATIC SYSTEM

• Bile is recycled via enterohepatic circulation (to LIVER, recycled)

Transporting Fat in the Blood

Fat is transported as lipoproteins with a lipid core and a shell composed of proteins, phospholipids, and cholesterol.

Lipoproteins

• Chylomicrons: transport of dietary triglycerides

• Very Low-Density Lipoprotein (VLDLs): produced by liver; release triglycerides

• Intermediate-Density Lipoprotein (ISLs): formed from the VLDL

• Low-Density Lipoprotein (LDLs): formed from IDL; contain mostly cholesterol

• High Density Lipoprotein (HDLs): pick up and recycle or dispose of cholesterol

Density (Protein & Lipid)

Related to the proportion of protein and lipid

• high density→ more proteins than lipids

Composition and Roles of the Major Lipoproteins in the Blood- Chylomicron

Primary Component: Triglyceride

Key Role: carries dietary fat from the small intestine to cells

Composition and Roles of the Major Lipoproteins in the Blood- VLDL

Primary Component: Triglyceride

Key Role: carries lipids both taken up and made by the liver to cells

Composition and Roles of the Major Lipoproteins in the Blood- LDL

Primary Component: Cholesterol

Key Role: carries cholesterol made by the liver and from other sources to cells

Composition and Roles of the Major Lipoproteins in the Blood- HDL

Primary Component: Protein

Key Role: helps remove cholesterol from cells and, in turn, excretion of cholesterol from the body; pick up cholesterol throughout the body

Lipoprotein Receptor Pathway

LDLs taken up by cells, broken down, and components utilized→ excess in blood become oxidized

Lipoprotein Scavenger Pathway

white blood cells remove oxidized LDLs; cholesterol can build up in these cells and kill them, resulting in plaque (atherosclerosis)

Properties of Fat in Foods

• Satiety

• Flavor

• Texture

• Absorption of fat-soluble vitamins

Hydrogenation of Fatty Acids

• Process used to solidify an oil

• Addition of H to C=C double bonds

• Formation of trans fatty acids

Cis Fatty Acid

causes the backbone of molecule to bend

Health Dangers of Excessive Trans Fatty Acids

• In 2015, the FDA ruled to restrict trans fatty acids from the diet

• Increases risk for heart disease

  • raises LDL

  • lowers HDL

  • increases inflammation

• FDA now requires on food labels

Rancidity

• Decomposed oils

• Breakdown of the C=C double bonds by ultraviolet rays, O₂

• Yields unpleasant odor, flavor, and sickness when consumed

• PUFA more susceptible

• Limits shelf life

Prevention of Rancidity

• Hydrogenation

• Addition of Vitamin E- reduced oxidation

• Addition of Butylated hydroxyanisol (BHA) and Butylated hyroxytolune (BHT)

Emulsifiers

Added to foods to improve texture

• Lecithins

• Monoglycerides

• Diglycerides

• Polysorbate 60

Recommendation for Fat Intake

• No RDA

• AI for Omega-6 is 17 g/day for men & 12 g/day for women

• AI for Omega-3 is 1.6 g/day for men & 1.1 g/day for women

American Heart Association’s Recommendations

• Limit total fat intake to 20-30% of total energy intake

  • NCEP liberalizes this recommendation to 35% of total energy if saturated and trans fats are limited

• Limit combined saturated and trans fat to 7-10% of total energy

• Limit cholesterol intake to 200-300 mg/d

Fat Replacement Strategies

• Water

• Starch derivatives

• Fiber

• Protein

• Engineered fats

Olestra (Olean)

• engineered fat

• fatty acids linked to sucrose

• not digested by enzymes or bacteria

• yields no calories

• addition of fat-soluble vitamins to structure

• over-consumption may cause cramping and loose stool

• may bind to carotenoids in the meal

Uses for Fat Substitutes

• use in moderation

• use in place of high fat option

• avoid over-eating

• treat it as you would a full-fat food

Cardiovascular Disease

• Leading cause of death in North America

• Symptoms take years to develop

• Plaque build-up can begin in childhood

• Myocardial infarction (heart attack)

• Cerebrovascular accident (stroke)

Plaque Formation

• Cardiovascular disease begins with the formation of plaques on blood vessel walls

• Contributors:

  • Smoking

  • Diabetes

  • Hypertension

  • Homocysteine

  • LDL

  • Blood vessel inflammation

Antioxidants Decrease LDL Oxidation

• Reduce LDL oxidation, thus slowing uptake by scavenger cells

• Food sources: fruits, vegetables, plant oils, nuts

• Controversy over supplementation

Progression of Atherosclerosis

• Plaque thickens as LDL, connective tissue, smooth muscle, and calcium are deposited in arteries

• Arteries harden and narrow

• Blood pressure affected by reduced elasticity of blood vessels

Terminal Phase of Atherosclerosis

Clot or spasm in blood vessel leads to heart attack or stroke

Risk Factors for Heart Disease

• Family history

• Smoking

• High blood pressure

• Total cholesterol >200 mg/dl

• HDL <40 mg/dl

• Diabetes

• Advanced age

• Lack of regular exercise and obesity

Lifestyle Interventions to Prevent Heart Disease

• Reduce dietary fat, trans fat, and cholesterol

• Increase MUFA and PUFA to recommended amounts

• Increase dietary fiber

• Increase activity; develop an exercise routine

• Adequate caloric intake to maintain healthy weight

Ratings of Blood Lipoprotein Levels (mg/dl)- Lipoprotein

< 200 = desirable

200-239 = borderline high

>/=240 = high

Ratings of Blood Lipoprotein Levels (mg/dl)- LDL Cholesterol

<100 = optimal

100-129 = near optimal

130-159 = borderline high

160-189 = high

>/=190 = very high

Ratings of Blood Lipoprotein Levels (mg/dl)- HDL Cholesterol

<30 = low

>/=50 = high

Ratings of Blood Lipoprotein Levels (mg/dl)- Triglycerides

<100 = optimal

100-149 = near optimal

150-199 = borderline high

200-499 = high

>/=500 = very high

Preventing CVD

• Total fat 20-35% total calories

• Saturated fat <7% total calories

• Trans fat low

• Polyunsaturated <10% total calories

• Monounsaturated <20% total calories

• Cholesterol <200 mg daily

• Include 2 g plant stanols/sterols daily

• Soluble fiber intake of 20-30g

• Keep body weight at a healthy level

• Increase physical activity