nutrition fats

Classification of Fats

• Types of Fats:

  • Triglycerides

  • Phospholipids

  • Sterols

Phospholipids

• Definition:

  • A type of fat that includes a phosphate group in addition to fatty acids.

• Structure:

  • Composed of two fatty acids, a phosphate group, and a glycerol unit.

• Properties:

  • Phosphate group is soluble in both water and fat.

• Function:

  • Key component of cell membranes, facilitating the movement of fats and water-soluble substances across membranes.

  • Phospholipids are non-essential; the body synthesizes them, particularly in the liver.

Sterols

• Definition:

  • A type of fat composed of hydrogen, carbon, and oxygen in a complex structure, distinct from fatty acids.

• Common Examples:

  • Cholesterol

  • Bile

  • Vitamin D

  • Sex hormones

• Cholesterol:

  • Synthesized by the liver; not essential in the diet.

  • Works in conjunction with bile; liver produces cholesterol for bile synthesis.

• Dietary Sources:

  • Found exclusively in animal products:

    • Meat

    • Eggs

    • Fish

    • Poultry

    • Dairy

  • Plant sources contain no cholesterol:

    • Peanut butter

    • Corn oil

    • Olive oil

    • Bread

Dietary Recommendations for Fat Intake

• General Guidelines:

  • Total fat intake should constitute 20-35% of total caloric intake.

  • Recommended intake: 30% of calories from fat (approximately 45 to 75 grams per day for a 2,000 calorie diet).

  • Types of fats to monitor:

    • Saturated fat: Should not exceed 10% of total caloric intake.

    • Trans fat: Recommended intake is zero.

• Food Labeling:

  • Examine total fat, saturated fat, and trans fat content on food labels to manage intake.

  • Example: Macaroni and cheese serves as a reminder to check serving sizes versus daily needs.

Saturated Fats from Common Foods

• High Saturated Fat Foods:

  • Pizza (two slices): 16 grams of saturated fat

  • Cheeseburger: 10 grams of saturated fat per serving; doubles if portion size increases.

  • Baked Goods: Can contain cholesterol depending on ingredients (e.g., butter, milk).

Digestion and Absorption of Fats

• Ingestion:

  • Mouth: No chemical digestion of fat; mechanical breakdown via chewing.

  • Stomach: Fat travels through without significant changes.

• Small Intestine:

  • Step 1: Emulsification by Bile

    • Produced in the liver, stored in the gallbladder; released into the small intestine when fat is present.

    • Bile emulsifies fats, breaking them into smaller droplets to mix with water so enzymes can act.

  • Step 2: Fat Digestion with Pancreatic Lipase

    • Enzyme secreted by the pancreas to digest fats after emulsification.

    • Converts triglycerides into free fatty acids for absorption.

• Absorption Process:

  • Small fatty acids can enter the bloodstream directly through the villi of the small intestine.

  • Larger fatty acids are packaged into chylomicrons to be transported via the lymphatic system.