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Questions and Answers
What is the scientific term for fats and oils?
What is the scientific term for fats and oils?
Lipids
Lipids are mainly made up of carbon, hydrogen and oxygen.
Lipids are mainly made up of carbon, hydrogen and oxygen.
True
What is the most common form of food fats?
What is the most common form of food fats?
Triglycerides
Which of the following are functions of fatty acids?
Which of the following are functions of fatty acids?
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When triglycerides are metabolized, the glycerol is converted to glucose.
When triglycerides are metabolized, the glycerol is converted to glucose.
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What determines the saturation of a fat?
What determines the saturation of a fat?
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Animal fats are mostly unsaturated fats.
Animal fats are mostly unsaturated fats.
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Which type of fatty acid is most common in foods?
Which type of fatty acid is most common in foods?
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Which of the following are examples of simple lipids?
Which of the following are examples of simple lipids?
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Sterols are made up of fatty acids and glycerol.
Sterols are made up of fatty acids and glycerol.
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What are phytosterols?
What are phytosterols?
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Cholesterol is a major component of all cell membranes.
Cholesterol is a major component of all cell membranes.
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Cholesterol is only obtained through animal foods.
Cholesterol is only obtained through animal foods.
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What are lipoproteins?
What are lipoproteins?
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High levels of LDL cholesterol are associated with an increased risk of heart disease.
High levels of LDL cholesterol are associated with an increased risk of heart disease.
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Which of the following are sources of dietary cholesterol?
Which of the following are sources of dietary cholesterol?
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Saturated fatty acids have double bonds between carbon atoms.
Saturated fatty acids have double bonds between carbon atoms.
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Which type of fatty acid has one or more double bonds between carbon atoms?
Which type of fatty acid has one or more double bonds between carbon atoms?
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Mono-unsaturated fatty acids have two or more double bonds.
Mono-unsaturated fatty acids have two or more double bonds.
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Name an example of a mono-unsaturated fatty acid.
Name an example of a mono-unsaturated fatty acid.
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Saturated fatty acids are typically liquid at room temperature.
Saturated fatty acids are typically liquid at room temperature.
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What is the location of the first double bond in omega-3 fatty acids?
What is the location of the first double bond in omega-3 fatty acids?
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Name a common source of omega-3 fatty acids.
Name a common source of omega-3 fatty acids.
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What are the main families of PUFA according to the position of the first double bond?
What are the main families of PUFA according to the position of the first double bond?
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Trans fats are unsaturated fats with hydrogen atoms bonded in the trans configuration.
Trans fats are unsaturated fats with hydrogen atoms bonded in the trans configuration.
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Excessive fat intake can lead to obesity.
Excessive fat intake can lead to obesity.
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Which of the following health problems are related to excessive fat intake?
Which of the following health problems are related to excessive fat intake?
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The Food and Nutrition Board recommends that people reduce their fat intake to 30% of total calories.
The Food and Nutrition Board recommends that people reduce their fat intake to 30% of total calories.
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Fats are essential for the absorption of fat-soluble vitamins.
Fats are essential for the absorption of fat-soluble vitamins.
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Fats provide a protective padding for vital organs.
Fats provide a protective padding for vital organs.
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Fats have a lower satiety value compared to other macronutrients.
Fats have a lower satiety value compared to other macronutrients.
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Cholesterol is necessary for the synthesis of some steroid hormones.
Cholesterol is necessary for the synthesis of some steroid hormones.
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Prostaglandins are recognized as local hormones.
Prostaglandins are recognized as local hormones.
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The incidence of atherosclerosis and coronary heart disease is high when blood cholesterol levels are over 250mg per 100ml.
The incidence of atherosclerosis and coronary heart disease is high when blood cholesterol levels are over 250mg per 100ml.
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Overweight people often suffer from sleep apnea.
Overweight people often suffer from sleep apnea.
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Excess weight increases the risk of developing fragile bones.
Excess weight increases the risk of developing fragile bones.
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The approximate fat requirements of individuals differ according to age groups.
The approximate fat requirements of individuals differ according to age groups.
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The Food and Nutrition Board recommends a fat intake of less than 10% of total daily calories.
The Food and Nutrition Board recommends a fat intake of less than 10% of total daily calories.
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A deficiency of dietary fats can lead to eczema and scaly skin.
A deficiency of dietary fats can lead to eczema and scaly skin.
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Fats are the primary sources of energy in the body.
Fats are the primary sources of energy in the body.
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Study Notes
Fats and Their Importance in Health and Nutrition
- Fats, also known as lipids, are a group of compounds characterized by a greasy feel and insolubility in water. They are soluble in some organic solvents.
- Fats are primarily composed of carbon, hydrogen, and oxygen.
- Fats are a more concentrated energy source, providing about two and a half times more energy than carbohydrates and proteins.
- Unlike carbohydrates, lipids have a larger proportion of hydrogen and carbon.
- Fats are solid at 20°C; otherwise, they are called oils.
- Simple fats and oils are crucial for food preparation, and the quality of the food product significantly depends on the types of fats and oils used.
- Triglycerides are the most common form of food fats.
- Over 90% of fats are in the form of triglycerides. Triglycerides consist of a glycerol backbone with three fatty acids esterified to the hydroxyl groups of the glycerol molecule.
- Fatty acids have a backbone made of carbon atoms. The number of carbon atoms and the number of double bonds between them vary. Butyric acid (C4:0), palmitic acid (C16:0), and arachidic acid (C20:0) are examples of fatty acids with varying carbon chain lengths.
- Fatty acids are the building blocks for triglycerides and phospholipids, a chain of carbon and hydrogen atoms with a carboxyl group at the alpha end and a methyl group at the omega end.
- There are 20 different fatty acids. They vary in length, saturation, and shape.
- Triglycerides comprise about 95% of food lipids and body lipids. Triglycerides are the storage form of fat.
- When caloric intake exceeds energy needs, triglycerides are stored in the body.
- All triglycerides have a similar structure; they consist of three fatty acids attached to a glycerol molecule.
- Glycerol is a short-chain carbohydrate molecule soluble in water.
- Triglycerides are important lipids found in both foods and the body, making up approximately 95% of lipids in food. They contribute to food texture, make meats tender, preserve freshness, and serve as energy storage in adipose tissue.
Fatty Acids
- Fatty acids are classified based on the number of carbon atoms in their alkyl chains.
- Short-chain fatty acids (SCFAs) have up to 5 carbon atoms and are liquid at room temperature. An example is butyric acid.
- Medium-chain fatty acids (MCFAs) have 6 to 12 carbon atoms and are also liquid at room temperature.
- Long-chain fatty acids (LCFAs) have 13 to 21 carbon atoms.
- Very long-chain fatty acids (VLCFAs) have more than 22 carbon atoms. They are mostly solid at room temperature.
Classification of Lipids
- Lipids are classified into simple lipids, compound lipids, and derived lipids.
- Simple lipids are esters of fatty acids with various alcohols.
- Fats are esters of fatty acids with glycerol. Oils are fats in liquid form.
- Waxes are esters of fatty acids with higher molecular weight monohydric alcohols.
- Compound lipids have at least one fatty acid replaced by carbohydrate, protein, or phosphorus, including phospholipids (which have phosphate), glycolipids (which have carbohydrates), and lipoproteins.
- Derived lipids are breakdown products of simple and compound lipids, including fatty acids, glycerol, steroids, other alcohols, fatty aldehydes, ketone bodies, hydrocarbons, lipid-soluble vitamins, and hormones.
Sterols
The key takeaway is that sterols are more complex than phospholipids or triglycerides. They are not made of fatty acids and glycerol but have a benzene ring structure.
- Cholesterol, a sterol, is a vital component of cell membranes and is needed for the production of sex hormones, bile acids, vitamin D, and steroid hormones.
- Cholesterol is endogenously made in the body, and also comes from animal products. High levels can contribute to heart diseases.
- Daily intake of cholesterol should not exceed 300 mg/day.
- Phytosterols are major plant sterols, that help with numerous body processes.
Lipoproteins
- Lipoproteins are responsible for transporting blood cholesterol.
- Low-density lipoprotein (LDL) cholesterol is a complex of lipids and proteins with more lipids than proteins. High levels of LDL cholesterol are associated with increased risk of heart diseases.
- High-density lipoprotein (HDL) cholesterol is a complex of lipids and proteins found in almost equal amounts, which transports cholesterol in the blood. High levels of HDL cholesterol are associated with a decreased risk of heart diseases.
Sources of Fats
- Animal fats are the major source of animal fats; examples include ghee, butter, milk, cheese, eggs, meat, and fish.
- Vegetable fats include those stored in seeds (e.g., groundnut, mustard, soybean, sesame, coconut, almond, cashew nut, safflower, and sunflower).
- Many other foods contain small quantities of fats that are not readily apparent (invisibly). Cereals, pulses, and vegetables are examples of these foods that contribute to total intake of fats in the diet.
Classification of Fats Based on Fatty Acids
- Saturated fatty acids contain single bonds between carbon atoms. They are typically solid at room temperature. Examples include fats from animal sources, coconut oil, and palm oil.
- Unsaturated fatty acids contain one or more double bonds between carbon atoms. They are typically liquid at room temperature. These are further categorized as:
- Mono-unsaturated fatty acids (MUFAs) - contain one double bond. Examples include oleic acid and fats from avocado, olive oil, peanuts.
- Poly-unsaturated fatty acids (PUFAs) - contain more than one double bond. PUFAs are further divided into Omega 3 (e.g. Alpha-linolenic acid (ALA), EPA, DHA), Omega 6 (e.g., linoleic acid (LA), arachidonic acid (AA)), and Omega 9 (e.g., oleic acid).
Double Bond Location in Unsaturated Fatty Acids
- Omega-3 fatty acids have the first double bond on the third carbon atom from the methyl end of the fatty acid. Examples are alpha-linolenic acid (ALA), EPA, and DHA.
- Omega-6 fatty acids have the first double bond on the sixth carbon atom from the methyl end of the fatty acid. Linoleic acid (LA) and arachidonic acid (AA) are examples.
- Omega-9 fatty acids have the first double bond on the ninth carbon atom from the methyl end. Oleic acid is primarily an example.
Cis and Trans Forms of Unsaturated Fatty Acids
- Naturally occurring unsaturated fatty acids are mainly in cis form, where hydrogen atoms are on the same side of the double bond. Trans forms have hydrogen atoms on opposite sides of the double bond. Trans fats are primarily produced through industrial processes.
Functions of Fats
- Energy: Fats are a concentrated energy source. One gram of fat provides 9 kcal.
- Thermal insulation: Subcutaneous fat acts as an insulator against cold by retaining body heat.
- Protein sparing action: Fats allow proteins to perform their function, such as growth and maintenance.
- Protection of vital organs: Fats protect vital organs like the heart, kidney, and intestine from physical shock.
- Absorption of Fat-soluble vitamins: Fats are essential for the absorption of fat-soluble vitamins (A, D, E, and K).
- Essential fatty acids: Examples include linoleic acid, linolenic acid, arachidonic acid, which are vital for maintaining healthy tissues.
- Satiety value: Fats are important in dietary satiety and satisfaction. A feeling of fullness in the stomach results from a high fat intake.
- Synthesis of hormones: Cholesterol is used in the production of certain hormones and bile acids (e.g., sex hormones).
- Precursors of prostaglandins: Polyunsaturated fatty acids act as precursors to prostaglandins (local hormones).
Effects of Excessive Fat Intake
- Obesity: Excess fat is stored in adipose tissue, potentially leading to obesity.
- Hypercholesterolemia and Coronary Heart Disease (CHD): High cholesterol levels increase the risk of CHD and atherosclerosis.
- Other related health problems: Excessive fat intake can negatively affect the heart, cause hormonal imbalances, possibly trigger diabetes, and contribute to sleep disorders as well as hip and knee problems.
Dietary Requirements of Fats
- Healthy individuals need to reduce their fat intake to 30% of their total calories. Lower intakes can lead to deficiencies.
Deficiency Symptoms of Fats
- Deficiency symptoms may include eczema, scaly skin, and growth deficiencies when fat intake is below 10% of total daily calories.
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