Fats and oils in the diet

Introduction to Fats and Oils

Welcome! In this chapter, we are exploring fats and oils. While people often think of fat as something to avoid, it is actually a vital nutrient that our bodies need to function correctly. Think of fats as your body’s long-term energy storage and a protective "bubble wrap" for your internal organs. In this guide, we will look at where fats come from, what they do for us, and how they behave when we cook with them.

What are Fats and Oils?

The main difference between a fat and an oil is simple: fats are usually solid at room temperature (like butter), while oils are usually liquid (like olive oil). Together, they are a major part of a balanced diet.

1. Sources of Fats and Oils

We get fats from two main places: animals and plants. Understanding where our food comes from is a big part of the Composition and value of the main foods section of your syllabus.

Animal Sources

These are fats that come from animals or animal products. Examples include:
• Dairy products: Butter, cream, and full-fat cheese.
• Meat: The visible white fat on a steak or the fat in bacon.
• Eggs: Specifically the yolk.
• Fish: Oily fish like mackerel or salmon.

Plant (Vegetable) Sources

These are usually oils extracted from seeds, nuts, or fruits. Examples include:
• Oils: Sunflower oil, olive oil, and rapeseed oil.
• Nuts and Seeds: Walnuts, peanuts, sunflower seeds, and sesame seeds.
• Pulses: Some beans, like soya beans, are high in fat.
• Fruits: Avocados are a rare example of a fruit high in fat.

Quick Review: Remember that "invisible fats" are those hidden inside foods (like nuts or cakes), while "visible fats" are things you can see (like the oil in a bottle or the fat on meat).

2. Functions of Fats in the Body

Why do we need to eat fats? They have several "superpowers" in our bodies:

• Energy: Fat is a concentrated source of energy. It provides more than double the energy of carbohydrates. It provides approximately \(9\) kcal per gram.
• Warmth (Insulation): A layer of fat under the skin (adipose tissue) helps keep our body temperature stable.
• Protection: Fat surrounds our vital organs (like the kidneys) to protect them from physical shock or injury.
• Fat-Soluble Vitamins: Certain vitamins—A, D, E, and K—can only be absorbed by the body if fat is present.
• Feeling Full: Fat takes longer to digest, which helps us feel satisfied after a meal.

3. Digestion and Absorption of Fats

Don't worry if this seems tricky at first! Digestion is just the body's way of breaking down big food pieces into tiny molecules it can use.

The Digestion Process

1. The Mouth and Stomach: Very little happens to fat here.
2. The Duodenum (Small Intestine): This is where the real work begins. Bile (made in the liver) is released. Its job is to emulsify fats—this means breaking large fat droplets into tiny ones so enzymes can work faster.
3. Enzymes: An enzyme called lipase breaks down the emulsified fat into fatty acids and glycerol.
4. The Ileum: The final part of the small intestine is the ileum. This is where the broken-down fat is absorbed into the body through tiny finger-like structures called villi.

4. Fats and Cooking

When we use fats and oils in the kitchen, they change how food tastes and how it reacts to heat.

Key Cooking Terms

• Smoking Point: This is the temperature at which a fat or oil begins to break down and give off a blueish smoke. If you reach this point, the fat will smell unpleasant and give the food a bitter taste.
• Rancidity: This is when fats and oils spoil over time. Exposure to light, air, and heat makes the fat "go off," resulting in a nasty smell and flavour.
• Frying: Using fats/oils to cook food quickly at high temperatures. (Refer to Chapter 6 for more on frying methods!)

5. Health and Diet Considerations

While fat is essential, having too much can lead to overnutrition. This can result in health problems such as:
• Obesity: Carrying too much body fat.
• Heart Disease: Certain types of fat can clog the arteries.
• Diabetes: Being overweight is a risk factor for Type 2 diabetes.

To stay healthy, students should remember the concept of a balanced diet—eating just enough fat for energy and protection without overdoing it.

Summary: Key Takeaways

• Sources: Can be animal (butter, meat) or vegetable (oils, nuts).
• Function: High energy (\(9\) kcal/g), protection, warmth, and carrying vitamins A, D, E, K.
• Digestion: Uses bile to emulsify and lipase to break down fat in the small intestine.
• Cooking: Watch out for the smoking point and rancidity.
• Balance: Essential for health, but too much can lead to obesity and heart issues.

Top Tip for the Exam: If a question asks why we cook with fat, don't forget to mention that it adds flavour, texture (like crispiness in fried chips), and helps conduct heat to the food!