Fats

LIPIDS (FATS)

WHAT FOODS CONTAIN FAT?

• Sources of Fat in Various Food Categories:
    - Dairy:
      - Cheese (1 oz): 9g
      - Whole milk (1 c): 8g
      - Sour cream (2 T): 5g
      - Butter (1 t): 4g
      - Nonfat yogurt (1 c): <1 g
    - Fats & Oils:
      - Olive oil (1 T): 14g
      - Salad dressing (2 T): 14g
    - Fruits:
      - Avocado (½ c): 11g
      - Berry pie (1 slice): 15g
    - Grains:
      - Croissant (1 med): 12g
      - Snack crackers (5): 4g
    - Vegetables:
      - French fries (1 c): 8g
    - Protein:
      - Peanuts (4 c): 18g
      - T-bone steak (3 oz): 11g
      - Salmon (3 oz): 5g

FOOD BASED FATS

1. Triglycerides - The main form of fat in foods and in the body.

2. Phospholipids: Formed from glycerol, fatty acids, and a phosphate group.

3. Sterols: A class of lipids with a distinctive ring structure.

TRIGLYCERIDES

• Structure:
    - Composed of one glycerol molecule and three fatty acid chains.

• Representation: The general structure is:
      $ext{Fatty acid} - ext{Glycerol}$
      H-C-OH
      H-C-C-C-C-C…Omega

FATTY ACIDS

• Characteristics: Fatty acids differ according to:
    1. Chain Length:
       - Short Chain: Fewer than 6 carbons
       - Medium Chain: 6-12 carbons
       - Long Chain: 14 or more carbons
    2. Degree of Saturation or Unsaturation:
       - Saturated (maximum hydrogen)
       - Unsaturated (lack of hydrogen at some parts, indicating double bonds)

FATTY ACID CHAIN LENGTH

• Short-chain fatty acids: <6 carbons

• Medium-chain fatty acids: 6-12 carbons

• Long-chain fatty acids: 14 or more carbons

• Digestive Effects:
    - Long chain fatty acids take longer to digest.
    - Higher melting point for longer chains.

SATURATED FATTY ACID

• Definition: A fatty acid carrying the maximum number of hydrogen atoms; there are no double bonds between carbon atoms.

UNSATURATED FATTY ACID

• Subtypes:
    - Monounsaturated Fatty Acids (MUFA): One double bond.
    - Polyunsaturated Fatty Acids (PUFA): More than one double bond.

COMPARISON OF FATTY ACIDS

• Saturated fatty acids stack well, leading to solid forms at room temperature, whereas MUFAs and PUFAs do not stack well and are liquids at room temperature.

• Illustrative Structures:
    - Saturated:
      $ext{CH}_2 ext{, C, CH}_3$
    - Monounsaturated:
      $CH_3(CH_2)_n CH=CH(CH_2)_m CH_3$
    - Polyunsaturated: Types with multiple double bonds.

TYPES OF FATTY ACIDS

• Key Examples of Fatty Acids:
    - Saturated: Animal fats and tropical oils (e.g., coconut oil, beef tallow).
    - Monounsaturated: Olive oil, canola oil.
    - Polyunsaturated: Safflower oil, flaxseed oil, corn oil, soybean oil.

CIS & TRANS FATTY ACIDS

• Cis Arrangement: This is the natural configuration for most unsaturated fats, resulting in a bent shape.

• Trans Arrangement: An altered configuration that can lead to health problems (noted in partly hydrogenated oils).

ESSENTIAL FATTY ACIDS

• Definition: Fatty acids that are essential for human health because the body cannot synthesize them and must be obtained from the diet.

• Types:
    1. Omega-3 Fatty Acids:
       - Examples: Alpha-linolenic acid (ALA), Eicosapentaenoic acid (EPA), Docosahexaenoic acid (DHA).
    2. Omega-6 Fatty Acids:
       - Examples: Linoleic acid, Arachidonic acid.

• Role: Used to produce eicosanoids which regulate various cellular functions.

SOURCES OF ESSENTIAL FATTY ACIDS

• ALA (Omega-3):
    - Sources: Flaxseeds, walnuts, canola oil, soybean oil, chia seed oil, fish & fish oil.

• LA (Omega-6):
    - Sources: Safflower oil, sunflower oil, corn oil, nuts, seeds, chicken.

PHOSPHOLIPIDS

• Structure: Two fatty acids and glycerol plus a phosphate group

• Role: Important in cell membranes, serve as emulsifiers that aid in fat transport and absorption.

• Examples: Bile and lecithin.

STEROLS

• Definition: A category of lipids characterized by their complex ring structures

• Cholesterol: Appear in cell membranes and are essential for health.
    - Function: Helps maintain membrane integrity, assists in hormone production, bile, and vitamin D synthesis.
    - Dietary Source: Present in animal foods such as eggs and meat; not necessary to consume directly as it can be synthesized in the body.

PHYTOSTEROLS

• Description: Plant-derived sterols that help lower blood cholesterol by reducing absorption in the intestines.

• Sources: Found in plant oils, nuts, seeds, beans, peas, lentils, and whole grains.

WHY EAT FAT?

• Functions:
    - Provides energy for immediate and stored needs (adipose tissue).
    - Essential for cell membranes and hormone synthesis.
    - Aids in the absorption and transportation of fat-soluble vitamins.
    - Enhances flavor and texture of food.

DIGESTION OF FATS

1. Mouth: Salivary glands produce lingual lipase, starting fat digestion.

2. Stomach: Fat becomes droplets; gastric lipase breaks down triglycerides.

3. Gallbladder: Releases bile into small intestine to emulsify fats.

4. Small intestine: Enzymes from pancreas digest to monoglycerides and fatty acids, transported in micelles for absorption.

ABSORPTION & TRANSPORTATION

• Lipoproteins: Transport vehicles for absorbed lipids—especially chylomicrons, which move fats from the intestines to cells and the bloodstream.

• Chylomicrons: Transport fat and are utilized by cells for energy, made into lipid compounds, or stored in fat tissue.

LIPOPROTEINS

• Two types:
    - Low-Density Lipoprotein (LDL): Considered “bad” cholesterol; potentially leads to plaque deposits and cardiovascular diseases.
    - High-Density Lipoprotein (HDL): “Good” cholesterol; scavenges LDL and removes it from circulation, offering protective effects against heart disease.

HEALTH EFFECTS OF FAT

• Monounsaturated & Polyunsaturated Fats:
    - Lower LDL cholesterol, reduce risk of cardiovascular disease, maintain brain health, reduce inflammation.

• Saturated and Trans Fats:
    - Raise LDL cholesterol and increase risk of cardiovascular disease.

EATING FAT - GUIDELINES

• Acceptable Macronutrient Distribution Range (AMDR): 20-35% of total calories as fat.

• Limit saturated fats to less than 10% of total calories.

• Essential fatty acid recommendations:
    - Males: 17g/day omega-6 and 1.6g/day omega-3
    - Females: 12g/day omega-6 and 1.1g/day omega-3

STRATEGIES FOR IMPLEMENTATION

• Prefer non-tropical plant oils, nuts, seeds, and fish.

• Consume at least two servings of fish weekly.

• Limit saturated fats from tropical oils, fatty meats, and full-fat dairy.

FISH & SEAFOOD RECOMMENDATIONS

• Use fish as a substitute for meat and poultry.

• Favor healthier cooking methods like baking, grilling, or broiling over frying.

UNHEALTHY FATS

• Sources of Unhealthy Fats:
    - Saturated & Trans fats include: high-fat meats, baked goods, full-fat dairy, fried foods, and palm/coconut oils.

HEALTHY FATS

• Types of Healthy Fats:
    - Monounsaturated fats: Found in avocados, olive oil, and certain nuts.
    - Polyunsaturated fats: Found in fatty fish and oils from various plant sources.

REPLACE BAD FATS WITH GOOD FATS

• Example meals:
    - Unhealthy Meal: 1 c fresh broccoli topped with 1 tbs butter, 4 oz grilled steak, and a mixed salad with bacon and blue cheese.
    - Healthier Meal: 1 c fresh broccoli sautéed in 1 tbs olive oil, 4 oz grilled salmon, and a mixed salad with avocado and sunflower seeds.

MEDITERRANEAN DIET PYRAMID

• This diet promotes whole grains, fruits, vegetables, nuts, legumes, and olive oil while limiting saturated fats and incorporating fish & poultry.

OMEGA-3 FATTY ACID CONTENT OF SELECTED FOODS

• Foods high in omega-3 include flaxseed oil, salmon oil, and various fish types with specific amounts of DHA and EPA.

REVIEW QUESTIONS

1. What are the functions of triglycerides in the body?

2. Which two fatty acids are essential?

3. Where are phospholipids found in the body?

4. What are some compounds that are made from cholesterol?

5. What types of fat are healthy? Unhealthy? Why?

6. What are the key features of the Mediterranean diet?