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Questions and Answers
What distinguishes saturated fatty acids from unsaturated fatty acids?
What distinguishes saturated fatty acids from unsaturated fatty acids?
Which type of fatty acid has a chain length of 2 to 4 carbons?
Which type of fatty acid has a chain length of 2 to 4 carbons?
What is a characteristic of polyunsaturated fatty acids?
What is a characteristic of polyunsaturated fatty acids?
What process creates trans fatty acids?
What process creates trans fatty acids?
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Which fatty acid type typically remains liquid at room temperature?
Which fatty acid type typically remains liquid at room temperature?
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What is the distinguishing feature of essential fatty acids?
What is the distinguishing feature of essential fatty acids?
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How many carbons are typically found in medium-chain fatty acids?
How many carbons are typically found in medium-chain fatty acids?
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What happens to the state of fatty acids during hydrogenation?
What happens to the state of fatty acids during hydrogenation?
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What component is replaced in the structure of phospholipids compared to triacylglycerols (TAGs)?
What component is replaced in the structure of phospholipids compared to triacylglycerols (TAGs)?
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What characteristic of the phosphate head of a phospholipid makes it hydrophilic?
What characteristic of the phosphate head of a phospholipid makes it hydrophilic?
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What role do phospholipids play due to their unique structure?
What role do phospholipids play due to their unique structure?
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Which is the main phospholipid found in food?
Which is the main phospholipid found in food?
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What is the primary function of cholesterol in the body?
What is the primary function of cholesterol in the body?
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How do plant sterols and stanols affect cholesterol absorption?
How do plant sterols and stanols affect cholesterol absorption?
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Where does the majority of lipid digestion occur in the body?
Where does the majority of lipid digestion occur in the body?
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Which substance stimulates the pancreas to release lipases during lipid digestion?
Which substance stimulates the pancreas to release lipases during lipid digestion?
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What is the role of alpha-linolenic acid (ALA) in the body?
What is the role of alpha-linolenic acid (ALA) in the body?
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Which of the following fatty acids is considered to be an omega-6 fatty acid?
Which of the following fatty acids is considered to be an omega-6 fatty acid?
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Why are partially hydrogenated oils (PHOs) considered unhealthy?
Why are partially hydrogenated oils (PHOs) considered unhealthy?
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What is the primary composition of triglycerides?
What is the primary composition of triglycerides?
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What function do phospholipids serve in the body?
What function do phospholipids serve in the body?
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Which deficiency signs might indicate a lack of essential fatty acids?
Which deficiency signs might indicate a lack of essential fatty acids?
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What is the effect of trans fats on health?
What is the effect of trans fats on health?
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Why are trans fats solid at room temperature?
Why are trans fats solid at room temperature?
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Which type of lipid is most common in food and the body?
Which type of lipid is most common in food and the body?
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What is a primary function of lipids in foods?
What is a primary function of lipids in foods?
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What are the components that make up a triglyceride?
What are the components that make up a triglyceride?
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Which type of fatty acid contains a hydrocarbon chain with only single bonds?
Which type of fatty acid contains a hydrocarbon chain with only single bonds?
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What role do phospholipids play in the body?
What role do phospholipids play in the body?
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How do lipids differ in their solubility in water?
How do lipids differ in their solubility in water?
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Which of the following is a function of cholesterol in the body?
Which of the following is a function of cholesterol in the body?
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What is the structure of fatty acids characterized by?
What is the structure of fatty acids characterized by?
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What is the primary role of bile in lipid digestion?
What is the primary role of bile in lipid digestion?
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Which substance is responsible for the final digestion of lipids into free fatty acids and monoglycerides?
Which substance is responsible for the final digestion of lipids into free fatty acids and monoglycerides?
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After lipid digestion, chylomicrons are formed from which components?
After lipid digestion, chylomicrons are formed from which components?
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What happens to free fatty acids and glycerol when the body needs energy?
What happens to free fatty acids and glycerol when the body needs energy?
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What is the role of micelles in lipid absorption?
What is the role of micelles in lipid absorption?
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Which of the following statements about cholesterol is true?
Which of the following statements about cholesterol is true?
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What is the acceptable macronutrient distribution range (AMDR) for fat in total caloric intake?
What is the acceptable macronutrient distribution range (AMDR) for fat in total caloric intake?
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How do foods rich in fiber influence blood cholesterol levels?
How do foods rich in fiber influence blood cholesterol levels?
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Study Notes
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.
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