Saturated, monounsaturated, polyunsaturated, trans fats, omega 3 fats, polyunsaturated fatty acids… It’s no wonder we feel confused about which fats we should be eating. In this article I will get to the fat chemistry, which influences their structure and stability to highlight which fats are best and why.

There are three main types of fats: saturated, monounsaturated and polyunsaturated fats and all have different fat chemistry. All fats are chains of carbon atoms linked by either a single or double bond. The differences between fats pertain to the chemical structure, in particular the length of the chain length and the number of double bonds or how saturated the fat is. Chain length and the number of bonds in the molecule dictate how a fat will behave. This influences things like whether it is a liquid or solid and room temperature and whether it will oxidise (go rancid) easily or not.

As a starting point remember this: Saturated fats are the most stable fats. They tend to be inert and don’t go bad regardless of temperature or when exposed to air.

Now let’s get into some sciency detail!

Saturated fats (saturated fatty acids – SFAs)

Need to know: Saturated fats are chains of carbons that contain no double bonds. Each carbon atom is bonded to a hydrogen atom

ie: Saturated fats are fully saturated with hydrogen bonds. Their saturated nature means they are stable; all of the atoms are bonded so they do not easily oxidise.

Nerd alert!

Saturated fats are straight chains of carbon with no double bonds so they pack together easily. This means they tend to be solid at room temperature and will get softer as they are heated. The saturated, stable structure of saturated fat means that they do not go rancid (oxidise) when they are exposed to heat, oxygen or light. This stability sets them apart from other fats.

The fact that they are saturated means they are less likely to lose an electron and cause oxidative damage to your body like other fats. Free radicals occur when loose bonds between atoms split and electrons are left without partners. These loose electrons can then react with other substances in the body and cause damage or ‘rusting’ (oxidation).

Examples of saturated fatty acids:

Long chain saturated fats

These are the primary structural fats that make up the human body (ie: 70-80% of fatty acids in most cells). It is the primary way that we store energy and is more easily burned than polyunsaturated fatty acids.

  • Palmitic aid: 16 -carbon long (palm oil, beef, eggs, poultry, seafood). Vital for formation for strong memory function.
  • Stearic acid: 18-carbon long (meat, eggs, chocolate). These are neutral LDL, and have been shown to increase HDL (good cholesterol).

Health benefits include:

  • Help absorb calcium into skeleton
  • Protect liver from damage by alcohol and toxins
  • Assist Cardio vascular function
  • May raise HDL (good cholesterol) and lower LDL (bigger particles)
  • Support immunity
  • Help absorb fat soluble vitamins A,D,K,E

Medium chain saturated fats (and medium chain triglycerides)

These are not stored in our fatty deposits as much as long chain saturated fats. They enhance fat burning and promote the development of ketones. MCTs have antiviral and antioxidant properties.

  • Lauric acid: 12 carbon long (coconut oil, palm oil, human breast milk).

Health benefits include:

  • Fat burning properties
  • Properties to heal gut irritation
  • They pass directly to the liver and are a good source of energy
  • Powerful protection against HIV and other viruses.

Despite the misinformation portrayed by government and industry, saturated fats are the most stable for cooking and the best for your body. They are the fats that we have eaten for thousands of years, so eat them liberally. They perform all sorts of important functions in the body as well as keeping you full and helping to regulate your blood sugar.

When it comes to cooking, saturated fats are by far your best bet. Use them to fill your food with flavour and to ensure it keeps you feeling full for longer. You will also get important minerals from many of these fats.

See my guide to fats for good sources of SFAs.

Monounsaturated fats (monounsaturated fatty acids – MUFAs)

Nerd alert!

MUFAs have one double bond in the carbon chains so they are less stable than saturated fats. They have a lower melting and smoking point and will more easily go rancid, oxidise or breakdown than saturated fats. They are more stable than polyunsaturated.

When these predominantly MUFA based oils go rancid they can be dangerous for your health. So keep them in the dark and only use them at a low heat or with no heat at all. (ie: for salad dressing).

Types of monounsaturated fats include:  Oleic acid (18 carbon molecule w one double bond).

Health benefits:

  • Good for your cardiovascular system
  • Reduce LDL cholesterol particles and triglycerides
  • Increase HDL (good cholesterol)
  • Reduce oxidation and inflammation
  • Lower blood pressure
  • Decrease thrombosis

Polyunsaturated fats (Polyunsaturated fatty acids – PUFAs)

Nerd alert!

These fats contain several double bonds so they are very unstable. Many (poly) of the bonds are not fully saturated with hydrogen because the carbon is already bonded to another carbon atom twice. There are kinks at the point of these unsaturated bonds, which means PUFAs do not pack together easily and tend to be liquid at room temperature. As a result of these unsaturated bonds PUFAs are very volatile when heated because the electrons can easily come loose in the body, which turns into free radicals.

PUFAs are made up of two types of omega-3s and omega-6s. Omega-3s occur naturally in things like seaweed and algae and also fish, because they eat these things. Omega-6s are found in nuts and seeds and the animals that eat them. As hunter-gatherers and throughout history we have eaten these types of PUFAs at a ratio of about 1:1.

Today most of the PUFAs we consume a ratio of about 1:10, sometimes 1:20 because of our consumption of vegetable and seed oils. This is problematic because omega-6s are pro-inflammatory while omega-3s are neutral. Try to eat foods rich in omega-3 PUFAs and avoid oils that have an unbalanced omega-3:omega-6 ratio.

Types of PUFAs: 

Omega-3 family (n-3)

Sources: Green leaves and algae and fish because they eat them

  • Alpha-Linoleic Acid (ALA)
  • Eicosapentaenoic Acid (EPA)
  • Docosahexaenoic Acid (DHA)

Although ALA is considered essential, most health benefits come from EPA and DHA.

Omega 6 family (n-6)

  • Linoleic Acid (LA)
  • Gamma Linolenic Acid (GLA)
  • Dihomo-Gamma-Linolenic Acid (DGLA)
  • Arachidonia Acid (AA)

Sources: Nuts and seeds and the animals that eat them.

Today most of our PUFAs come from heavily processed vegetable oils, industrialised seed oils. During manufacturing these oils are heated to very high temperatures to extract the oil from substances that are not naturally very fatty.

Today’s PUFA oils are very high in omega-6s and low in omega-3s. These vegetable oils are dangerous for our health and should be avoided, particularly where they are used for deep-frying which makes them highly vulnerable to oxidation and the production of free radials.

How are vegetable and seed oils made?

Vegetable and see oils are made through a highly intensive chemical and mechanical process to extract oil from the original product, giving them a volatile fat chemistry. The high temperatures kill the nutrients in the seeds and the final oil product oxidises very easily. I have described this process in another article.

Trans fats

Trans fast are the result of a process called hydrogenation. To make vegetable oils solid at room temperature, the hydrogen atoms are rearranged at the point of the double bonds. Yes, we are manipulating the chemical structure of the fat. This could be described as genetically modifying it and the health consequences are great.

The process creates trans double bonds by moving the hydrogen atom to the other side of the carbon chain at the point of the double bond. These two hydrogen atoms then balance each other and the fatty acid becomes straight and the fat becomes more ‘plasticy’ and has a much higher melting temperature. 

The hydrogenation process creates a trans fatty acid that is similar to natural fats and so the body can readily incorporate them into its cells. However, their altered chemical structure means that any of the saturated or unsaturated benefits are lost and this fat chemistry can wreak havoc on our cell metabolism. Additionally the presence of several unpaired electrons means that it can cause trouble with a lot of the body’s chemical reactions.

Hydrogenated oils are just one molecule away from being a plastic. This is product that is held up as a healthy alternative to butter!

The decision to eat fat from whole foods (meat, butter and coconut oil) should be an easy choice now that you know the cold, hard and hydrogenated truth about vegetable oils.

Final words on fat chemistry

In this post we have delved to the depths of fat chemistry of those in our diets. While you probably won’t remember that stearic acid has 16 carbons that isn’t what’s important. What you need to remember is the fat that comes from nature, beef dripping, butter and coconut oils, are the most stable fats you can use for cooking. They are the kindest to your body and the least likely to cause inflammation.

If something doesn’t look like oil in its natural state (ie a vegetable or a sunflower), then it has gone through a long and involved chemical process to become the golden bottled oil you find in the supermarket.

You have the fat chemistry facts and you have logic. Make wise decisions!

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