5.4 — Fats

Composition, States and Sources

• Fat is an organic carbon compound containing carbon, hydrogen and oxygen.
• Fat is an important class of food in the human diet.
• Fats exist as solids or liquids:
  • Solid fats at room temperature usually come from animals such as chicken, cow, goat and fish.
  • Liquid fat is called oil and normally comes from plants, such as palm oil, coconut oil and soya bean oil.

Saturated and Unsaturated Fats

Similarities

• Organic compounds containing carbon, hydrogen and oxygen.
• Insoluble in water.
• Important sources of fatty acids in the body.

Saturated fat	Unsaturated fat
Mainly from animals	Mainly from plants
Solid at room temperature	Liquid at room temperature
High melting point	Low melting point
Maximum number of hydrogen atoms in the molecule	Number of hydrogen atoms in the molecule is not maximum
Cannot accept additional hydrogen atoms	Can accept additional hydrogen atoms

Effects of Excessive Fat Intake on Health

• Fat is an important component of a balanced diet, but excessive fat—especially saturated fat—raises blood cholesterol.
• Animal sources such as cheese, eggs, butter and meat contain high levels of cholesterol.

Importance of cholesterol

• Builds body-cell membranes.
• Used to synthesise bile and sex hormones.
• Used to produce vitamin D in skin exposed to sunlight.

Effects of excessive cholesterol

• Gallstones and jaundice: cholesterol forms gallstones that block the bile duct; a blocked bile duct can cause jaundice.
• Atherosclerosis: cholesterol deposits on the inner artery wall and narrows the lumen, disrupting or blocking blood flow.
• Atherosclerosis can cause hypertension, stroke—when an artery leading to the brain is blocked or bursts—and a potentially fatal heart attack.

Prevention

• Reduce saturated-fat intake.
• Consume unsaturated fats, which can lower blood cholesterol levels.