This is the first in a series of three posts that looks at the role of fats and oils in our diet. This first post breaks down the different types of fat that you see on food labels: saturated, unsaturated and trans. The second and third posts will look into the highly topical omega-3 (found especially in oily fish) and omega-6 fats (found especially in seeds and their oils).
I’m writing this series in response to requests from several different readers, on similar themes. If you’ve made a request for a different post subject that I haven’t addressed yet, I thank you for your input and I will get to your topic soon!
What are fats?
Let’s start at the very basic. Fats and oils are essentially two words that refer to the same thing. We call them ‘fats’ when they’re solid at room temperature (think the fat on meat, or lard), and ‘oils’ when they’re liquid at room temperature. Fats are a essential component of our diet.
The following are all 80-100% fat:
- Vegetable oil, olive oil, sunflower oil, coconut oil etc
- Fish oil
- Cod liver oil
- Ghee (‘clarified butter’)
- Fat on meat
Fats and energy
Like carbohydrates and protein, fats give us energy. You may have heard the terms ‘calories’ or ‘kilojoules’. We measure the energy in food in calories or kilojoules, depending on whether you use an imperial or metric system. Energy in food goes towards maintaining our body weight, and gives us the energy to do all the things we do each day. If we don’t get enough energy from food, we lose weight. If we eat too much, we gain weight.
Different types of fat
On a sub-microscopic level, fats are made up of millions of smaller components, called molecules. The molecules in fat are called ‘fatty acids’.
There are several different types of fatty acid. You may have come across these on the Nutrition Information Panels of food products when you’re at the supermarket. The main types of fatty acid are: saturated, monounsaturated, polyunsaturated and trans. Or, more simply, saturated and unsaturated.
All fats/oils contain a mixture of these types of fatty acid. For example, if we look at the Nutrition Information Panel of one brand of butter (see image below), we see that although butter contains 80.5 grams of fat per 100g of butter (80.5% fat), “only” 53.1 grams of this is saturated fatty acids. So although the majority of fat in butter is saturated, some of it is unsaturated.
Saturated fatty acids
Solid fats are high in saturated fatty acids. These are usually animal fats, although coconut and palm oil, and cocoa butter, are also high in saturated fatty acids. (Coconut and palm oil are only called ‘oils’ because they are liquid at room temperature in their native tropical climate; they are solid at room temperature in temperate climates)
A diet high in saturated fats increases “bad” LDL-cholesterol, and increases your risk of having a heart attack. Public health bodies around the world recommend minimising the amount of saturated fats in our diet. I mentioned in the last post that current average intakes of saturated fat in the West are almost double the Heart Foundation’s recommendations (12% versus 7%).
Major sources of saturated fat in the average Westerner’s diet include:
- Meat, including bacon and processed meats
- Cream and sour cream
- Full-cream milk and yoghurt
- Regular fat cheese
- Coconut milk and coconut cream
- Pies and pastries
Choosing reduced fat milk, yoghurt and cheese is a great way to reduce the amount of saturated fat you eat, and still get enough calcium.
Unsaturated fatty acids
Liquid oils are high in unsaturated fatty acids. Foods high in unsaturated fatty acids include oils, nuts and seeds (i.e. they’re from plants). They’re also found in their derivatives, such as margarine and similar spreads, peanut butter and tahini. Eating a handful of nuts and/or seeds every day is good for our health.
There are two main types of unsaturated fatty acids: monounsaturated and polyunsaturated.
Monounsaturated fatty acids
Good sources include:
- Plant oils, including canola, olive & soybean
- Nuts and seeds
- Peanut butter
Polyunsaturated fatty acids
Consist of omega-3 and omega-6 fatty acids. Good sources include:
- Seed oils (such as canola, sunflower or flaxseed)
- Oily fish (such as mackerel, herring/kippers, sardines, salmon, trout, tuna)
- Walnuts and Brazil nuts
- Wheat germ
As a simple summary, trans fats are produced when plant oils are chemically altered to become solid. In the process, the unsaturated fats turn into trans fats. Trans fats are even worse for your heart than saturated fats. They are found in old-style margarines and any food where you see the words “partially hydrogenated” in the ingredients list. For more information, see my summary about trans fats in my last post.
Importantly, low-fat diets are no longer recommended. Instead, there is strong evidence to support replacing saturated fats with unsaturated fats, but still eating a moderate amount of fat. In general, this means eating fewer foods high in animal fats, and more nuts, seeds and plant oils. Aim for a handful of nuts on most days. In the case of milk, cheese and yoghurt, this means choosing reduced fat options.
- Try to minimise the amount of saturated fats in your diet.
- Try to have more unsaturated fats in your diet.
- (In general: less animal fat; more plant oils, nuts and seeds)
- Low-fat diets are no longer recommended. Instead, a way of eating that is high in unsaturated fats (plant oils, nuts and seeds) and low in saturated fats (animal fats) is recommended.
If you have any questions, or want clarification, please comment below.
Next post, I’ll explore Omega-6 fatty acids and seed oils, which have received a lot of bad press lately. Stay tuned!
Disclaimer: The summary provided above is for the general public, and should not replace advice given by a dietitian or doctor. If you need dietary advice tailored to your individual circumstances, consult your GP or Accredited Practising Dietitian (APD).