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Questions and Answers
What are the main types of lipids?
What are the main types of lipids?
Triglycerides, phospholipids, and sterols.
Which of the following is a characteristic of lipids?
Which of the following is a characteristic of lipids?
What is the primary component of dietary fat?
What is the primary component of dietary fat?
Triacylglycerol
What are the basic units of fat?
What are the basic units of fat?
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Glycerol is a type of fatty acid.
Glycerol is a type of fatty acid.
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What is the process called where three fatty acids combine with one molecule of glycerol?
What is the process called where three fatty acids combine with one molecule of glycerol?
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Which type of fatty acid has the maximum possible number of hydrogen atoms?
Which type of fatty acid has the maximum possible number of hydrogen atoms?
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What type of fat is found in animal foods, like meat and poultry?
What type of fat is found in animal foods, like meat and poultry?
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The human body can synthesize all the essential fatty acids it needs.
The human body can synthesize all the essential fatty acids it needs.
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What two fatty acids are considered essential for human beings?
What two fatty acids are considered essential for human beings?
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What is the primary difference between unsaturated fatty acids and saturated fatty acids?
What is the primary difference between unsaturated fatty acids and saturated fatty acids?
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What type of fatty acids have one or more points of unsaturation?
What type of fatty acids have one or more points of unsaturation?
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What is the scientific abbreviation for polyunsaturated fatty acids?
What is the scientific abbreviation for polyunsaturated fatty acids?
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Monounsaturated fatty acids are typically found in animal sources.
Monounsaturated fatty acids are typically found in animal sources.
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How are fatty acids and glycerol linked together?
How are fatty acids and glycerol linked together?
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What is the main function of bile in fat digestion?
What is the main function of bile in fat digestion?
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What is the primary site of fat digestion?
What is the primary site of fat digestion?
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Match the following lipoproteins with their primary function:
Match the following lipoproteins with their primary function:
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A high blood cholesterol level is usually associated with high LDL.
A high blood cholesterol level is usually associated with high LDL.
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What is the primary storage form of fat in the body?
What is the primary storage form of fat in the body?
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What is the primary function of essential fatty acids?
What is the primary function of essential fatty acids?
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What is the main difference between visible fats and invisible fats?
What is the main difference between visible fats and invisible fats?
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Which of the following is a major source of saturated fatty acids in the Malaysian diet?
Which of the following is a major source of saturated fatty acids in the Malaysian diet?
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Palm oil is primarily composed of unsaturated fatty acids.
Palm oil is primarily composed of unsaturated fatty acids.
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Which types of fish are commonly consumed by Malaysians and are known to be rich in EPA and DHA?
Which types of fish are commonly consumed by Malaysians and are known to be rich in EPA and DHA?
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Trans fatty acids are naturally occurring in foods.
Trans fatty acids are naturally occurring in foods.
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What is the main reason for hydrogenation of unsaturated fats?
What is the main reason for hydrogenation of unsaturated fats?
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What is the recommended dietary intake of total fat for adults?
What is the recommended dietary intake of total fat for adults?
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Study Notes
Lipids: Fats and Oils
- Lipids are a family of compounds that include triglycerides (fats and oils), phospholipids, and sterols (cholesterol).
- Fats are solid at room temperature.
- Oils are liquid at room temperature.
- Lipids are characterized by their insolubility in water.
- Dietary fat is primarily made up of triglycerides (98%) with smaller amounts of phospholipids and sterols.
Fatty Terms
- Triglycerides are the main class of dietary lipids, including fats and oils.
- A triglyceride is composed of three units of fatty acids and a single glycerol unit.
- Fatty acids are basic units of fat, consisting of carbon chains with an acid group on one end and hydrogen atoms attached throughout the length.
- Glycerol is an organic compound that forms the backbone for triglycerides.
Classification of Fat
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Fats are categorized as saturated, monounsaturated, and polyunsaturated.
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Saturated fats: Animal fats (lard, butter, palm, palm kernel, coconut)
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Monounsaturated fats: Olive oil, canola oil, peanut, avocado
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Polyunsaturated fats: Corn, soybean, cottonseed, safflower, sunflower, fish oils
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Fatty acids can vary in carbon chain length.
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Long-chain fatty acids: 12-24 carbons, found in meat, fish, and vegetable oils.
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Medium-chain fatty acids: 6-10 carbons, found in dairy products.
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Short-chain fatty acids: less than 6 carbons, found in dairy products.
Saturated Fatty Acid
- A saturated fatty acid has the maximum possible number of hydrogen atoms (no points of unsaturation).
- Found in animal foods (meat, poultry, and full-fat dairy) and tropical oils (palm, coconut).
- The body can synthesize saturated fatty acids (e.g., palmitic acid) for physiological and structural functions.
- Recommended Dietary Intake (RNI) for dietary fat (adults) is 25-30% of energy.
Unsaturated Fatty Acid
- Unsaturated fatty acids have one or more points of unsaturation, meaning they have fewer hydrogen atoms than saturated fatty acids.
- Found in both plant and animal sources.
- Further divided into monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs).
Monounsaturated Fatty Acids
- Contain one point of unsaturation.
- Mostly found in vegetable oils (olive, canola, peanut).
- Oleic acid (18:1 n-9) is a major type of MUFA.
- Important for membrane structural lipids, especially in nervous tissue myelin.
Polyunsaturated Fatty Acids (PUFAs)
- Contain two or more points of unsaturation.
- Found in nuts, vegetable oils (safflower, sunflower, soybean), and fatty fish.
- Linolenic acid (omega-3) and linoleic acid (omega-6) are two important types.
Essential Fatty Acids (EFAs)
- Cannot be synthesized by the body in sufficient amounts.
- Linoleic acid (omega-6) and linolenic acid (omega-3) are essential PUFAs crucial for human beings.
- The body can use linoleic acid to make arachidonic acid (important in gene regulation).
- The body can also use linolenic acid to make eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
- Omega-3 fatty acids (DHA, EPA) are protective against blood clots, inflammation (arthritis, asthma), irregular heart rhythm, and cancer.
Trans Fatty Acid
- Created when an unsaturated fat is hydrogenated to increase shelf life.
- Primarily found in margarines, shortenings, commercial frying fats, and baked goods.
- Linked to heart disease in research.
- Unsaturated fatty acids can be either cis or trans, depending on the arrangement of hydrogen atoms around the point of unsaturation.
- Cis: hydrogen atoms on the same side.
- Trans: hydrogen atoms on opposite sides.
Phospholipids
- Important for cell membranes.
- Act as emulsifiers in the body, joining water and fat.
- Used in foods like margarine, chocolate, and salad dressings to keep fats dispersed.
- Common in many foods.
Sterols
- Include bile acids, sex hormones, adrenal hormones, and vitamin D.
- Cholesterol is a sterol found only in animal foods.
- Cholesterol is made in the liver.
- Cholesterol is a necessary component of cell membranes, influencing membrane fluidity.
- Dietary cholesterol intake is recommended to be 300 mg/day
Characteristics of Fats
- Animal fats generally have high melting points and are solid at room temperature due to a high saturated fatty acid content.
- Plant fats, in general, have lower melting points and are liquid at room temperature due to a higher unsaturated fatty acid content, with some exceptions.
- Seed oils (e.g., coconut oil, palm kernel oil) are exceptions and have a high saturated fat content.
- Trans fats have physical properties similar to saturated fatty acids.
Digestion, Absorption and Transport of Fat
- Fat digestion begins in the stomach.
- The stomach’s churning action mixes fat with water and acid, with small amounts of fat being broken down.
- In the small intestine, bile (produced by the liver and stored in the gallbladder) emulsifies fat, breaking down large fat globules into smaller droplets.
- Enzymes (pancreatic lipase) break down triglycerides into fatty acids and glycerol.
- Fats are absorbed into lymphatic vessels as chylomicrons which carry them to body cells.
- Short- and medium-chain fatty acids and glycerol can be absorbed directly into the bloodstream.
- Chylomicrons transport dietary fat from the small intestine to the body cells.
- VLDL transports triglycerides made or packaged by the liver to various tissues.
- LDL carries cholesterol to body cells (high LDL levels can indicate high blood cholesterol).
- HDL carries cholesterol from body cells back to the liver for recycling.
Functions of Fat
- Energy source: Provides 9 calories/gram, a major energy storage form.
- Satiety and palatability: Contributes to a feeling of fullness and food flavor.
- Carries fat-soluble vitamins (A, D, E, K).
- Organ padding and insulation: Protects organs and provides insulation.
- Hormones synthesis: Essential for hormone production.
- Contributes to aroma and flavor in food.
- Eicosanoids (compounds created from EFAs): regulate muscle function, blood vessels and blood clots, response to injury and infection, and various other biological processes in the body.
Food Sources of Fat
- Dietary fats are categorized as visible (cooking oils, spreads and butter) and invisible fats (naturally occurring in food).
- Common visible fats include plant-based cooking oils, vegetable oils, and animal fats (butter).
- Common invisible fats include fats in cereals, vegetables, fruits, pulses, nuts, and seeds; dairy products, meat, eggs, and seafood.
- Palm oil is a major cooking oil in Malaysia.
- Coconut oil is a significant source of saturated fat in Malaysian cuisine.
Fat Contents in Malaysian Foods
- Malaysian diets commonly include fish rich in omega-3 fatty acids (EPA and DHA).
Deficiency and Excess of Fat
- Fat deficiency is rare in Malaysia, but can happen due to malabsorption (inhibition of bile salts), malnutrition related to chronic disease (leading to low blood levels of EFAs), or liver disease.
- Symptoms of fat deficiency can include growth retardation, skin lesions, reproductive failure, and liver disorders.
- Excess fat intake, largely due to affordability of high-fat foods and sedentary lifestyles, is a significant concern in Malaysia, increasing the risk of obesity.
- According to the National Health and Morbidity Survey of 2015, about 17.7% of the Malaysian population was obese, and approximately 30% were overweight.
- Excess intake of fat can lead to various health issues, not just obesity, but also problems with blood cholesterol.
Effects on Blood Lipid Levels
- Saturated and trans fats increase total and LDL cholesterol and may decrease HDL.
- Polyunsaturated fats may decrease total and LDL cholesterol but may increase HDL.
- Monounsaturated and omega-3 fats may decrease total and LDL cholesterol but increase HDL.
Lipids and Health
- Oxidized LDL cholesterol can be a major contributor to atherosclerosis, a condition in which plaque builds up inside the arteries, reducing blood flow.
###How Much Fat to Consume?
- Recommended ranges for total fat, saturated fat and omega fatty acids for different age/life stages.
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