Lipids

Triglycerides

(AKA: triacylglycerols) Consist of: Three fatty acid chains attached to One glycerol backbone Majority of lipids in the diet (95%) and the storage form of fat in the body.

Medium-chain fatty acids

6-12 carbon atoms in length. It can travel in the portal bloodstream bound to either the transport protein albumin or a phospholipid.

long-chain fatty acids

14 or more carbon atoms in length

Short-chain fatty acids

< 6 carbon atoms in length. It can travel in the portal bloodstream bound to either the transport protein albumin or a phospholipid.

lipoproteins

A spherical compound in which fat clusters in the center and phospholipids and proteins form the outside of the sphere.

What are the recommendations for fat?

AMDR: 20-35% of total calories AMDR for High Activity Levels: 20-25% of total calories Saturated Fat: <7% of total calories Trans Fat: Absolute minimum Linoleic Acid: 5 - 10% of total calories Alpha-linolenic Acid: 0.6 - 1.2% of total calories Linoleic : alpha-linolenic acid: ≤3:1, 5:1 - 10:1

Types of Fat and Stability

All fats spoil when exposed to oxygen, light and heat, but the degree of saturated impacts their stability and susceptibility to rancidity Saturated fats: the tightly packed fatty acids chains result in a more stable fat that is more resistant to oxidation The slower oxidation of saturated fat means that it is more shelf stable for processed foods. The more unsaturated a fatty acid is, the more quickly is spoils when exposed to air, heat and light. Polyunsaturated fatty acids are more susceptible to spoilage because of the greater number of C-C double bonds.

Risk factors for cardiovascular disease

Being overweight, Elevated blood cholesterol levels, Physical inactivity, Smoking, High blood pressure, Diabetes mellitus, and Inflammation

Hormone involvement of lipid digestion

CCK and Secretin: both produced by the small intestine; they act on the gallbladder, causing it to contract. CCK also stimulates the contraction of digestion enzymes from the pancreas

Diets high in saturated fats

Decrease the removal of LDLs from the blood which leads to high blood cholesterol levels. Contribute to the formation of plaques that can block arteries. 1% increase in dietary saturated fatty acids, 2% increase in LDL cholesterol, and 2% increase in heart disease risk.

In food supply

Calorie source (most nutrient dense macronutrient), provides nutrients (Vitamins and omega 6 and 3), acts as an emulsifier (helps diverse fat evenly in foods), provides texture and flavor to foods, helps keep food moist, helps us feel satiated for longer (protein --> fats --> carbs) Source of essential fatty acids and fat-soluble vitamins

Diets high in trans fatty acids

Can raise blood levels of LDL-cholesterol as much as saturated fat. 1% decrease in dietary saturated fatty acids, 2% decrease in LDL cholesterol, and 2% decrease in heart disease risk.

Plant sterol

Certain foods have been fortified with plant sterols. Interfere with absorption of animal cholesterol. May help lower blood cholesterol levels because of their apparent ability to interfere with animal cholesterol absorption. FDA health claim for plan sterols; need 0.65 grams twice daily to see an effect. Most commonly fortified in butter, also milk, cheese and some meal replacement products.

Low Density Lipoprotein (LDL)

Composed mainly of cholesterol, transports endogenous fats (esp. Triglycerides) from liver into the tissue, involved in regulating endogenous cholesterol production. Comes from VLDL (bad cholesterol)

Bile

Composition: bile salts (from cholesterol), lecithins, and other phospholipids and electrolytes (NA,K, Mg, Ca) Produced by the liver and stored in the gallbladder Function: breaks fats down into smaller pieces Fates: Reabsorbed into ileum/blood or trapped in fibers and excreted.

Blood Lipid profile

Concentration of lipids in the blood. Blood cholesterol after a meal. Total Cholesterol: < 200 mg/dL LDL: <100 mg/dL HDL: ≥ 60 mg/dL Triglycerides: <150 mg/dL

What is the relationship between fat intake and obesity? Are low fat foods necessarily better?

Consequence of high-fat, high-kcalorie diets in excess of energy needs. Low-fat or fat-free foods not always healthier options

Trans-Fatty Acids

Dietary Sources: Naturally occurring trans fats are found in full fat dairy products (like milk) and red meat (EX: Conjugated Linoleic Acid) Most occurs during hydrogenation. FDA requires labeling for conventional foods and some dietary supplements *Taken off of GRAS* and *decrease HDL cholesterol.* Plan is to remove artificially created trans fats from the food supply, although companies can apply and provide justification why their product(s) should include trans fat. Don't forget to check the ingredients list to see if it is hydrogenated or partially hydrogenated to see if it really has trans fats. Effects of health has lead to "trans fat ban"

Cardiovascular disease

Dysfunction of the heart or blood vessels. Heart Cath

Medicines help reduce risk

Endogenous cholesterol synthesis inhibitors: statins Bile acid sequestrants Nicotinic acid

In the body

Energy: both immediate and stored energy; fat is a major fuel source at rest. We can store unlimited amounts of fat unlike CHO and protein Structural component: phospholipids which provide flexibility and integrity Insulation and shock protection: protects organs such as the heart and kidneys from temperature extremes. Mechanism for absorption of phytochemicals and fat-soluble vitamins. Keeps skin and hair healthy

Simple vs mixed triglycerides

Exists as solids or oils according to fatty acid structure (Anima fat: 40%-60% saturated; 30%-50% MUFA and PUFA Plant: 10%-20% saturated, 80%-90% MUFA and PUFA) (MUFA: Monounsaturated fatty acids; PUFA: Polyunsaturated Fatty acids)

Lipid

Fats don't make you fat like peas don't make you pea. Insoluble in water which make it difficult for digestion, by generally soluble in organic solvents. Classes: Triglycerides, phospholipids, sterols, and Vitamins A,D,E, K. (Organic solvents include acetone, ether, chloroform)

Invisible fats

Fats hidden within foods. They occur naturally or are added during processing (EX: Baked goods, dairy, meats, fast foods)

Visible fat

Fats we add to foods; we can see how much fat (Ex: Butter, cream, mayonnaise, salad dressings)

Phospholipids

Glycerol backbone+2 fatty acids chains+ phosphate group (hydrophilic head) Manufactured by our bodies. Lecithin: *Major cell membrane constituent *

Lipids absorption

Happens in brush border

Lifestyle Changes to Lower cvd risk

Maintain normal blood glucose level, Eat throughout the day, Moderate alcohol intake, Maintain an active lifestyle, Maintain a healthful body weight, and Decrease salt intake (DASH diet)

Saturated

Hydrogen atoms surround every carbon in the chain. Saturated with hydrogen atoms (max number of hydrogen atoms; no carbon-carbon double bonds) Solid at room temp because the are packed tightly together. *mostly from animal sources* (EX: animal fats, butter, lard are all high in saturated fatty acids). More resistant to oxidation. Decreased rancid food likelihood so it increases shelf time (EX: palmitic acid and stearic acid). Since saturated fats do not have C-C double bonds, they don't have to worry about the kink in the chain formed for a cis- arrangement.

Digestion Challenges

Hydrophobic lipids and Hydrophilic enzymes

Enteroheptic Circulation

In the lever, bile's make from cholesterol, in the gallbladder bile's stored, the small intestine bile emulsifies fats and then it meets its fate (see above)

Essential Nutrients

Key word: essential. Linoleic acid (omega 6) Forms arachidonic acid that is found by Counting from the methyl end, the C-C double bond is found on the 6th carbon. Conditionally essential fatty acids (Found in veggies and nut oils). Can increase inflammation. Alpha linoleic acid (omega-3 fatty acid): EPA and DHA (found in veggies, soy, fatty cold water fish, flaxseeds, and walnuts) that has the C-C double bond on the 3rd carbon. They are separated by the placement of their double bond. EFAs cannot be made by the body because the body is unable to synthesize c-c double bonds before the 9th carbon. EFAs must come from the diet

Monounsaturated and polyunsaturated fatty acids

Lack of hydrogen atoms. Have at least one carbon-carbon double bond. 1 carbon-carbon (Double = the point of saturation.) 2 Types: Monounsaturated Oleic Acid (olive and canola oil) (mono = 1 carbon-carbon double bond) and Polyunsaturated (poly = > 1 carbon-carbon double bond) Linoleic acid and alpha-Linolenic acid

Dietary cholesterol

Less effect on blood cholesterol than saturated and trans fat. Many foods high in cholesterol are also high in saturated fat. Food sources: Egg yolks, milk products, meat, poultry and shellfish

Unsaturated Fatty acids

Liquid at room temperature because they are not stocked together well, they are long and straight. Hydrogen atoms at the unsaturated point can be arranged in different position. Cis: same side of carbon chain (liquid at room temperature). Arrangements result in a *kink* in the fatty acid chain at the carbon-carbon site, preventing the chains from stacking tightly together. Trans: opposite sides of the chain (looks like saturated acids with long straight chain). Plays role in structure and function (EX: flaxweed). Slightly less susceptible to spoilage.

Lipoprotein Lipase (LPL)

Location: located in surface of muscles and adipose tissue (circulatory system) Function: disassembles triglycerides on the chylomicrons from muscles and adipose tissue to pull fats for use. Fate: Used for Energy, storage, or turned into compounds. Become smaller and denser as TG move off the chylomicron and into the cell, eventually turning into the chylomicron remnant. When it reaches this certain size it goes back to the liver (chylomicron remnant contains 20% of fat it had in the beginning) Remnant is eventually taken up by the liver. Chylomicrons are cleared fairly rapidly; a meal containing a moderate amount of fat will be cleared from the blood within 6-8 hours after consumption

Eicosanoids

Made from omega 6 and 3 fatty acids. Reduce inflammation, plaque build up, blood clotting and plasma triglycerides. Prostaglandins, thromboxjnes, and leukotrienes that reduce inflammatory responses. May reduce risk of heart disease: Reduce blood clotting and plansma triglycerides

Very low density VLDL

Made primarily by the liver, transports triglycerides (mostly), cholesterol, and phospholipids (contains most fat in center) to the tissues and blood in the system

Dietary cholesterol

Main type of sterol. (exogenous) Found ONLY in animal foods. (EX: meat, eggs, fish, poultry, and dairy products. Made in our bodies in sufficient amounts so its non-essential. Liver produces 800-1500 mg/day, used for production of sex hormones, vitamin D, and bile; can't live without it. When you add a fatty acid chain it becomes a cholesterol ester. Many cells make cholesterol, but the liver is the major producer of cholesterol

Small intestine

Majority of digestion. Secreted by bile and pancreatic lipases: brakes triglycerides into 2 free fatty acids and a monoglyceride. Hormone: CCK and secretin, other lipids: phospholipids, cholesterol, and cholesterol esters (loosing fatty acid chains). Making fats smaller. Majority of lipid digestions takes place Bile: emulsifies fat = brings the hydrophobic fats and the hydrophilic enzymes together.

Triglyceride Products of digestion

Monoglyceride + 3 fatty acid chains (broken down by lipoprotein)

Sterols

Multiple carbon atoms rings. Plays major role in sex hormones. Sterols are found in both plant and animal foods

Beneficial fats

Omega-3 fatty acids acids may reduce inflammation and blood triglycerides but may be low in diets. Good sources include fish, walnuts, soy, canola and flaxseed. Recommendation: Switch to more healthful fats without increasing total fat intake. Use olive or canola oil in place of butter or margarine Select low-fat or nonfat dairy product

Short and medium chain fatty acids absorption

Packaged onto micelles, diffuse into enterocyte and micelles are broken down, SCFA and MCFA are then absorbed directly into blood stream

Chylomicrons

Part of the lipoprotein family that are Produced primarily in the small intestine. It's the group of transporters responsible for transporting lipids through the body Purpose: transports exogenous (dietary) fat to the muscles and adipose fat (Composition) Outer shell: contains proteins and phospholipids, both water soluble, that allows transportation of fat through the body Inner core: reformed triglycerides and cholesterol esters

lecithins

Primary emulsifiers in bile. Hydrophobic tails attract lipid droplets, dispersing the fat into smaller molecules of fat that repel one another This allows the fat to be exposed to lipase enzymes for digestion

Fat replacers

Purpose: to lower the fat content of foods while duplicating the taste and texture of fats Found in chips, cakes, cookies, ice cream, etc. Type of fat replacer used depends on the product. May cause GI side effects in large amounts

Micelles

Purpose: transportation of lipid products out of the intestinal lumen and into the enterocyte. Contains a hydrophobic core and a hydrophilic surface to allow the transportation of lipids through the watery gut environment. Composition: bile salts + digested lipid products (including free fatty acids, free cholesterol and the monoglycerides).

hydrogenation

Reduces oxidation, resits rancidity = more shelf life, makes oils more solid and more saturated creates trans fatty acids (straight rigid compounds) By adding the hydrogen you straighten out the bend making them more stable. Hydrogen atoms are added to unsaturated fatty acids under high temperatures and pressures Trans fats occurs when hydrogenation changes the hydrogen next to carbon-carbon double bond from cis to trans configuration Artificial trans fatty acids occur when only some of the C-C double bonds are broken

High Density Lipoprotein

Reverse cholesterol transporter (muscles -->liver) to be excreted. Composed primarily of protein. Removes free cholesterol from extra hepatic tissues and returns them to the liver (good cholesterol)

Protection from rancidity

Sealing in airtight containers (expensive and not done very often), add Antioxidants (which compete for oxygen, which decreases the exposure of oxygen molecules to the fatty acid chain) and hydrgenation

How does the level of saturation of a fatty acid affect its shape and the form it takes at room temperature?

Shape is determined by the saturation of the carbon chains Saturated fats are packed tightly together, meaning they are more likely to be solid at room temperature Examples of saturated fats: animal fats, butter, lard are all high in saturated fatty acids Unsaturated fatty acids: don't stack together well = liquid at room temp

Phospholipids role In body

Soluble in water due to a *hydrophilic head* and fat due to a *hydrophobic tail*. Keep fat suspended in blood and other body fluids. Enable lipid transport across the cell membrane. Allows hormones and fat soluble vitamins transport. Phosphate group contains a molecule of choline, which is a vitamin like compound classified with the nutrients involved in energy production

Polyunsaturated fats

Spoils most readily

Long chain fatty acids and Monoglycerids

Step 1: micelles diffuse into enterocyte (releases fatty acids, monoglycerides and cholesterol) Step 2: Digestion products enter cell. (reform triglycerides and cholesterol esters) Step 3: Reform digested products, Step 4: Package newly formed contents onto chylomicrons (takes 30 mins to 3 hours to reach this point) (the lymph empties into the bloodstream through the thoracic duct at the left subclavian vein in the neck) Step 5: Chylomicrons move out of the enterocyte and into the lymph

Average lipid content of diet

TG: 50-100 grams Phospholipids: 4-8 grams Cholesterol: 200-350 milligrams

Mouth/Stomach

The lingual lipase in the mouth start lipid but it's a minor component. Stomach: gastric lipase holds up in low pH; mechanical shear force as chyme leaves stomach via pyloric sphincter

High-Fat Diets and Cancer

Three types of cancer have been studied extensively for their possible relationship to dietary fat intake: Breast cancer, Colon cancer, and Prostate cancer While Fat does not initiate cancer development it may promote cancer growth Omega-3 fatty acids may protect against some cancers

Dietary Fat recommendations

Too little fat can be detrimental to health Fatty Acid Deficiencies Rare in U.S. and Canada At risk populations: Infants and children with fat-free or low-fat diets and Individuals with eating disorders Symptoms: Skin lesions, growth retardation, kidney lesions, early death

Dietary Changes to Lower cvd risk

Total fat: 20−35% total calories Saturated fat: less than 7% total calories Cholesterol: less than 300 mg per day Trans fat: reduce to absolute minimum Increase omega-3 fatty acids Dietary fiber: 20−30 grams per day Folate: 400 micrograms/day Moderate alcohol intake: 2 drinks per day for men, 1 drink per day for women. Alcoholic beverages like red wine also contain beneficial phytochemicals shown to help lower CVD risk. These changes may also benefit cholesterol profiles by lowering the LDL cholesterol and increasing HDL cholesterol.

What steps can be taken to lower risk for certain cancers?

Until the links with cancer are settled, the American Institute for Cancer Research recommends these common-sense rules: Maintain a healthy body weight, Engage in moderate physical activity at least 30 min/day, Limit consumption of sugary foods, empty Calories, red meats, salty foods, and alcohol, Eat a variety of fruits, vegetables, and whole-grain foods

Phospholipids Roles in food

Used as emulsifiers (Ex: Salad dressings, mayonnaise, candy bars)

Familial Hypercholesterolemia

Very high blood cholesterol, characterized by high LDL levels Cause: mutant genes decrease LDL receptors on liver Result: unable to effectively remove LDL remnants from blood and the Liver continues to synthesize cholesterol, further increasing blood cholesterol Consequences: Premature heart disease Treatment: Bile acid binding resins, Statin medications, and Liver transplant Brown & Goldstein

Cholesterol ester Products of digestion

common in foods, fatty acid is removed by cholesterol esterase in order to be absorbed into the body. The Ester replaces a hydrogen with an alkyl or of other organic group

Atherosclerosis

accumulation of cholesterol in the arteries. Can result in heart attack or stroke

Phospholipids Products of digestion

broken down into smaller, more absorbable units like triglycerides

All fatty acids contain

carboxyl end and methyl end. Determines method of lipid digestion , absorption, metabolism, and use

Fatty acids classified by

chain length, saturation level, and shape

Triglycerides: Shape

determined by the saturation of the carbon chains: Saturated or Unsaturated

Fatty acid chain lengths

important because it determines the digestion/absorption method and affects how triglycerides are metabolized and used within the body.

Cholesterol Products of digestion

no digestion takes places