Untitled Quiz

Fats and Other Lipids

• Lipids include fatty acids, triglycerides, phospholipids, and cholesterol
• Lipids function in the body and in foods
• Saturated, monounsaturated, polyunsaturated, and trans fatty acids differ chemically
• Essential fatty acids, phospholipids, and cholesterol have specific roles in the body
• Lipids are digested, absorbed, and transported in the body

Lipids Overview

• Lipids are generally insoluble in water
• Lipids are less dense than water
• Lipids include fatty acids, triglycerides, and phospholipids

Types of Lipids

• Triglycerides are the most common lipids in food and the body
• Triglycerides are composed of fatty acids and glycerol
• Phospholipids make up cell membranes and act as emulsifiers
• Sterols, including cholesterol, have carbon rings

Major Lipid Functions in the Body

• Lipids provide and store energy (fat)
• They maintain cell membranes and produce hormones
• Lipids insulate the body and cushion against bumps
• They contribute to body contours, absorb and store fat-soluble vitamins & phytochemicals

Lipids in Foods

• Lipids enhance the absorption of fat-soluble vitamins and phytochemicals
• They impart rich flavor, smooth texture, and appetizing aroma to foods

Fatty Acids

• Fatty acids have a hydrocarbon chain with a methyl group (CH3) at one end and an acid group (COOH) at the other end
• Fatty acids vary in the number of carbons
• Short-chain fatty acids have 2-4 carbons
• Medium-chain fatty acids have 6-12 carbons
• Long-chain fatty acids have 14-24 carbons

Fatty Acids (cont.)

• Saturated fatty acids have all single C-C bonds, holding the maximum number of hydrogen atoms
• Unsaturated fatty acids have at least one or more double bonds in the carbon chain
• Examples include monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA)
• Trans fatty acids are created by hydrogenation of unsaturated fats, resulting in a more saturated and solid state

Fatty Acids and Their Structures (cont.)

• Saturated fatty acids have a straight chain structure
• Monounsaturated fatty acids have one double bond, causing a bend in the chain structure
• Polyunsaturated fatty acids have more than one double bond, leading to a more kinked structure

Essential Fatty Acids

• Essential fatty acids cannot be made in the body and must be obtained from diet
• Two essential fatty acids are alpha-linolenic acid (ALA) and linoleic acid (LA)
• ALA is an omega-3 fatty acid, LA is an omega-6 fatty acid
• The body uses these acids to make docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and arachidonic acid (AA)

Triglycerides

• Triglycerides are composed of 3 fatty acids attached to a glycerol backbone
• They are approximately 95% of lipids in the body and in foods

Comparing Fatty Acid Contents of Common Fats and Oils

• Various typical fats and oils have different proportions of saturated, monounsaturated, polyunsaturated, and other lipids.

Phospholipids

• Phospholipids are similar to triglycerides, except they have a phosphorus-containing group instead of a fatty acid
• Phospholipids act as emulsifiers, mixing oil and water together
• Lecithin is a common phospholipid found in egg yolks, liver, wheat germ, peanuts, and soy

Sterols

• Sterols have carbon atoms arranged in rings. Cholesterol is the most well-known sterol.

Sterols (cont.)

• Cholesterol is produced by the liver and is used to make vitamin D, steroid hormones and bile
• Plants produce sterols, along with stanols, which are not well absorbed by the intestines. They might reduce cholesterol absorption

Lipid Digestion and Absorption

• The duodenum is the main site of lipid digestion
• CCK stimulates the pancreas to release lipases
• Bile salts aid in the digestion of lipids, emulsifying large fat droplets to small droplets
• Glycerol, fatty acids and monoglycerides form micelles to transport lipids into absorptive cells.
• Micelles help digest lipids to absorptive cells
• Chylomicrons are formed to transport lipids to the bloodstream

Lipid Absorption

• Micelles transport lipids to absorptive cells
• Triglycerides are formed, along with cholesterol and protein to form chylomicrons
• Chylomicrons enter the lymphatic system and bloodstream

Lipid Transport

• Chylomicrons are a type of lipoproteins that transport lipids in the lymphatic and bloodstream.

Summary of Lipid Digestion, Absorption, and Elimination

• Digestion of lipids happens mainly in the small intestine
• The liver, gallbladder, and pancreas play major roles in lipid digestion and absorption
• Undigested fat is excreted in the feces

Recycling Bile Salts

• Used bile salts are most often recycled
• Bile salt absorption is blocked by soluble fiber
• Recycling of bile salts can lower blood cholesterol levels

Using Triglycerides for Energy

• Adipose cells break down and reform triglycerides (fat) when cells need energy
• Cells take fatty acids from the blood stream and use them, after breakdown
• The liver converts glycerol to glucose for energy

Lipid Consumption

• Fat contributes significantly to the daily caloric intake in Jamaica, as well as other countries
• Acceptable macronutrient distribution ranges (AMDR) suggest 20-35% fat intake of total calories
• Saturated fat intake is recommended to be less than 10% of total calories

Nutrition Facts Panels: Lipids

• Total fat, saturated fat, trans fat, cholesterol are listed on Nutrition Facts panels

Lipoproteins and Atherosclerosis

• Lipoproteins transport lipids in the blood and play major roles in the development of atherosclerosis.
• There are four types: chylomicrons, VLDL, LDL, and HDL.
• Chylomicron, HDL, LDL, VLDL have different roles in transporting and carrying different types of lipids and protein.

HDL, LDL, and VLDL

• High-density lipoprotein (HDL) (good cholesterol) transports cholesterol from tissues to the liver, contributing to the reduction of blood cholesterol level
• Low-density lipoprotein (LDL) (bad cholesterol) carries cholesterol to tissues, contributing to plaque buildup in arteries, increasing risk of atherosclerosis.
• Very-low-density lipoprotein (VLDL) plays a role in contributing to the development of atherosclerosis.

Atherosclerosis and CVD

• Atherosclerosis is characterized by plaque buildup in arteries
• Plaque buildup results in impaired blood flow
• Plaque buildup in arteries can lead to Cardiovascular Disease (CVD).

Major Risk Factors

• Nonmodifiable risk factors for CVD include age and genetics
• Modifiable risk factors for CVD include unhealthy diet, hypertension, pre-diabetes, obesity, lack of physical activity, tobacco use, and sleep apnea.

Assessing Your Risk of Atherosclerosis

• A lipoprotein profile measures cholesterol and triglycerides to assess atherosclerosis risk
• Desirable levels include low total and LDL cholesterol, a high HDL and triglycerides levels.

Diet and CVD Risk

• Saturated fats increase total cholesterol.
• Trans fats increase LDL but decrease HDL
• Monounsaturated fats lower LDL.
• Polyunsaturated fats lower total cholesterol and LDL, but usually do not promote atherosclerosis
• Diet plays a role in CVD

Omega-3 and Omega-6 Fatty Acids

• Omega-3 (ALA, DHA, EPA) sources include fatty fish, seeds, nuts, and algae
• Omega-3 acts to reduce inflammation, blood clotting, and blood pressure
• Omega-6 (LA) sources include vegetable oils and whole grains. Omega-6 may increase inflammation and blood clotting and has a controversial role in heart disease

Reducing the Risk of CVD

• Strategies to reduce unhealthy fats include reducing fried foods and using egg whites instead of eggs.
• Leaner cuts of meat and choosing low fat alternatives can also help to lower intake of unhealthy fat

Summary (cont.)

• Triglycerides are the most common lipid type in the body.
• Most food provides some triglycerides, often a mix of fatty acids.
• The structure of phospholipids is similar to a triglyceride structure but has a phosphorus and often nitrogen group
• The duodenum is a key site in digestion of lipids as it needs lipase and bile salts
• Micelles and chylomicrons help with transport of lipids to the bloodstream and lacteals.