An easy-to-understand guide about the basics of nutrition. If you want to follow a healthy lifestyle, this is the best place to start from!
Fats, fats, fats…oh, the famous fats! We have all heard of them, but do you actually know what they are? What do they do? Are they really that bad for us? Well, look no further! Today, I will try to give you a bit of a background on fats and hopefully answer some common questions that often lead us to the wrong eating habits.
What are fats?
Fats are components of food, just like its fellows carbohydrates and proteins (you can check the posts I wrote about carbohydrates and proteins here and here). They are a source of energy, or fuel, for the body and they are very energy dense (1g of fat provides 8.8 kcal). This means that each gram of fat we eat will supply a generous amount of energy (in the form of calories) and therefore, if eaten in large amounts will lead to weight gain more quickly than other food components. It also means though, that it takes more energy to metabolize (or “burn”) 1 g of fat and burning fats will lead to the loss of more calories. Apart from being a great source of energy, fats play an important role in providing structure to the cell membranes and in the regulation of biochemical reactions within the cells.
Are fats good or bad for us?
Fats are an essential component of our diet and we do need them. However, certain kind of fats (saturated and trans) have been linked to an increased risk of heart disease and stroke, as they increase the amount of bad cholesterol (LDL) in our body. Why is LDL cholesterol bad? Because, it can build up in the blood vessels, blocking them and causing them to narrow. This will in turn lead to strokes and heart attacks. In order to reduce the building up of bad cholesterol in blood vessels, we need the good HDL cholesterol to come to the rescue! HDL cholesterol removes the bad LDL cholesterol from the veins and takes it to the liver instead. And guess what? Unsaturated fats help to maintain bad cholesterol at bay! That’s why we should try to reduce the amount of saturated fats we consume and instead substitute them with unsaturated fats.
Polyunsaturated fats, which include the essential omega-3 and omega-6 fatty acids, have also been linked to several other health benefits, like reducing inflammation, improving cognitive functions, reducing the risk for diabetes, some cancers, depression, arthritis and osteoporosis.
Different kinds of fat
I need you all to be familiar with the term “fat” and have a good idea about its chemical structure (I promise, I will keep this as simple as possible so that each one of you can understand and not fall asleep in front of your computer). I will supply lots of lovely photos to make this part more enjoyable :). Spoiler alerts: there will be some pictures with jokes.
This is a fat:
Hold on, hold on, just focus on the colours. There are two colours here, right? Green and red, that’s all you need to see for now. Fats are also called triglycerides (which make up 95% of the fat found in food) , the reason being that they are made of a glycerol backbone (see the part in green), with three fatty acids attached to it (tri-glycerides). Each red chain is a fatty acid. As you can see, each fatty acid chain has numerous C written in it and a lot of H around it. “C” stands for carbon and “H” for hydrogen. They are all linked together through one single line, which represents a single bond between the carbon and the hydrogen atoms. Those single lines (aka bonds) will determine what kind of fat we are dealing with.
Fats (triglycerides) can be saturated, unsaturated (monounsaturated and polyunsaturated) or trans (which are not very common in nature and are mainly the results of food manufacturing), depending on which fatty acids they are made of.
The picture below shows a saturated fatty acid. As you can see there are only single lines between the “C” and “H” in the fatty acid chain. Only single bonds, easy peasy.
Now, let’s have a look at an unsaturated fatty acid.
I will play a game with you now, can you spot the differences between the two fatty acids above? As you can see, in the unsaturated fatty acid there is one “=” between two carbons and two “H” missing. That means that there is one double bond, which causes the fatty acid to bend. Because there is only one double bond, this particular fatty acid is called monounsaturated (mono = one). A polyunsaturated fat will have more than one double bond and will look something like this:
Here, there are 3 double bonds.
The position of the double bond in the chain plays an essential part in the nomenclature of the fatty acid. Have you ever heard of omega-3, omega-6 and omega-9 fatty acids? Well, can you guess why they are called like that? Look at this picture:
The first one (a) is a saturated fat, so we don’t need to worry about that. The second one (b) is an omega-6 fatty acid. The first H you see on the left is the end of the fatty acid chain (also known as “omega” end). From there, if you count in order going left to right how many C there are, you will see that at the 6th C there is a double bond. That is why, it’s called omega-6. The 6th carbon atom from the omega end has a double bond. There is also another double bond if you keep counting on the carbon atoms, which means it’s a polyunsaturated fatty acid, get it? The position of the second or third double bonds you encounter, will determine the name for that specific omega-6. There are different kind of omega-6 fatty acids, for example linoleic acid and arachidonic acid.
Now, if you look at the last fatty acid in the picture above (c) you will see that the carbon bond is positioned at the third carbon atom from the omega end (going left to right). And guess what? That is why it’s called omega-3! Yaaay! It all makes sense now (I hope)! Again, there are different kinds of omega-3, depending on the position of the other carbon atoms in the chain, the most common being eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The length of the chain, also plays an important role in the nomenclature of the fatty acid, as it will determine whether it’s a short, long or medium chain fatty acid. But we are not going there now, don’t worry.
Linoleic acid (omega-6) and alpha-linolenic acid (omega-3), are called essential fatty acids, because our body cannot synthesize them, as it lacks the enzymes required to introduce the double bonds at the 3rd and 6th carbon. Therefore, it is essential that we introduce them in our diet.
Another joke, to give you a bit of a break. Hahaha, I promise it’s the last one..maybe.
I want to tell you something really interesting, now. From the picture below, you can see that saturated fatty acids (a) are all made of a straight chain with no double bonds, right ?
This, allows all the different saturated fatty acid chains to stick together next to each other, with little room in between. That’s why at room temperature most saturated fats have a solid composition. Whereas, unsaturated fatty acid chains (b), usually bend and they leave gap in between each other, moving around. And that explains why unsaturated fats are usually liquid, at room temperature. I love science! Saturated fatty acids, are usually found in animal fats, such as butter, lard, meat but can also be found in vegetable fats, such as coconut oil. Unsaturated fats, on the other hand, are usually vegetable fats and are present in the form of oils, such as olive oil, rapeseed oil, corn oil, but again, they can be found in animals. For example, omega-3 fatty acids are found in fish oil.
Going to the last kind of fatty acid, “trans” or “hydrogenated”, let me tell you something. First of all, they are not very common in nature. So where do you find them? Well, mainly in processed foods. You see, trans fats are natural occurring unsaturated fats (oils), that undergo a process called hydrogenation. Through this process, the double bonds naturally occurring in between carbon atoms, are eliminated by adding extra hydrogen atoms to the carbons. Look at the picture below:
Can you see how the hydrogenated fat looks like a saturated fat now? This process allow oils, which are liquid in nature, to become solids. One perfect example is margarine, or fat spreads. Have you ever wondered how an “olive oil spread” could be solid? Well, now you know how!
So far, I have talked about triglycerides, which make up 95% of fat found in food. The remaining 5% is made up of phospholipids and other minor components. Phospholipids are essential components in cell membranes and like the other fats are hydrophobic, which means they do not mix with water. Joke below: the red spot on the left is water, now you can laugh, or cry! Haha 😀
Phospholipids are added to many foods, such as mayonnaise, because of their emulsifying properties. Also, their chemical structure differs from the one of triglycerides. And this is what they look like:
But enough with the chemistry, now and well done for following me all the way here!
Where can fats be found in food?
All food contains fats that are both saturated and unsaturated. Foods that contain a higher amount of saturated fats are full-fat dairy products, fatty meats and some processed foods.
Unsaturated fats can mostly be found in vegetable oils, avocados, nuts and seeds.
Polyunsaturated fats provide the essential omega-3 and omega-6 fatty acids we require and can be found in oily fish, such as salmon, sardines, mackerel and in smaller amounts in some vegetable oils, such as linseed, flax and walnuts.
What is the daily recommended intake for fats?
No more than 35% of your daily intake should come from fat. As a guideline, men should consume 95g of fat each day (of which, no more than 30g should be saturated) and women 60g a day (of which, no more than 20g should be saturated).
That’s it for today, my lovely friends. I hope you found this useful and look out for my next “Nutrition Explained” posts!
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Have a great day!
Ooops, I nearly forgot..
Note: All pictures have been taken from Google images and Pixabay, I do not own any rights to the pictures in this post.