Fats
Food Preparation & Nutrition: AQA GCSE, topic 2.1.3
Why Do We Need Fats?
We need fats for the following reasons:
Provide energy
- Fats are concentrated energy sources.
- We get double the amount of energy per gram of fat than we do per gram of carbohydrate or protein.
Cholesterol
- We use fat to form cholesterol.
- Cholesterol - a vital component of cell membranes.
Source of vitamins
- Fats contain vitamins A, D, E and K (in fat-soluble form).
Provide insulation
- Fat helps us to keep warm by creating an insulating layer beneath the skin.
- Our bones and our organs are protected by these layers.
Saturated and Unsaturated Fats
Triglycerides make up fats. Triglycerides are esters formed from fatty acids and glycerol.
Saturated and unsaturated fatty acids
- Fatty acids are chains of carbon atoms bonded to hydrogen atoms.
- There are two types:
- Saturated fatty acids - contain single C-C bonds only.
- Unsaturated fatty acids - contain one or more C=C double bond.
Saturated and unsaturated fats
- During digestion, the human body breaks down fat into fatty acids.
- If there are more saturated fatty acids, it's a saturated fat.
- If there are more unsaturated fatty acids, it's an unsaturated fat.
Saturated fats
- Saturated fats are unhealthier than unsaturated fats.
- Eating lots of saturated fat can raise cholesterol levels and put us at greater risk of heart disease.
- We mostly get saturated fats from animal sources, like beef and dairy sources. Palm oil is an example of a plant-based source.
- At room temperature, saturated fats tend to be solid.
Unsaturated fats
- Unsaturated fats are the healthier of the two.
- We mostly get unsaturated fats from vegetable sources with high-fat content, like pecans, pumpkin seeds and avocados.
- At room temperature, unsaturated fats tend to be soft or liquid.
- There are two types of unsaturated fats:
- Monounsaturated - have one C=C double bond. We get them from hazelnuts and avocados among other things.
- Polyunsaturated - have two or more C=C double bonds. We get them from walnuts and flax seeds among other things.
Lowering cholesterol
- Research shows that a person can lower their cholesterol by eating unsaturated fats instead of saturated fats.
How Much Fat Do We Need?
Our bodies need enough fat to work properly. But too much fat in the diet can be harmful.
Dietary reference values
- Government guidelines - less than 35% of our daily food energy intake.
- Less than 11% should come from saturated fat.
- Average adult - around 70g of fat per day.
- No more than 20g of this should be saturated fat.
- The majority of UK residents consume more fat than this.
Consequences of too much fat
- Gaining weight.
- Obesity, which can lead to type 2 diabetes.
- Excess saturated fat can raise cholesterol levels.
- Cholesterol restricts the flow of blood around the body by clogging up blood vessels.
- A person will be more likely to suffer from high blood pressure, shortage of breath or coronary heart disease.
Consequences of too little fat
- Vitamin deficiency, as the body doesn't get enough of the fat-soluble vitamins A, D, E and K.
- Thinner fat layers beneath the skin for protection. So bones may bruise more easily if knocked.
- Less insulation.
- If someone isn't eating enough carbohydrates, the body will resort to using fat stores to get energy. The person may lose weight if they're not eating enough fat.
Test yourself on Fats
Why do we need fats?
Which vitamins are found in fats?
How does the amount of energy provided per gram of fat compare to the amount of energy per gram of carbohydrate or protein?
Which of the following vitamins is NOT found in fats?
What type of chemical compound are triglycerides?