Fats (or lipids) are a type of nutrient with structural and metabolic functions. But not all fats are created equal and not all fats have the same impact on our health.
Did you know that some vitamins are fats? When it comes to fats, what is best for our health: an “alpha” or an ”omega”, a “cis” or a “trans”? Why can’t be live without eating fats? Why is olive oil healthier than coconut oil?
If you continue reading, I will explain why the properties of fats depend on their structure, so that you can make better informed dietary choices.
Structurally, fats are molecules formed of chains of atoms of carbon and hydrogen. Depending on their core structure, they are divided into two main types: the glycerides (derived from glycerol) and the fatty acids. Typically, whenever we eat any fatty food, our enzymes break down the fat into these two types of components.
Furthermore, fatty acids are molecules that usually exist in their “ester” forms: triglycerides, phospholipids and cholesteryl esters. Triglycerides are the main constituents of our body fat and skin oils, and when in blood they serve as a carrier of fat to the liver. Phospholipids make up most of our cell membranes. Cholesteryl esters are what we commonly known as “blood cholesterol”. This is why your doctor checks all these different types of lipids in your annual blood works, because they reflect on different areas of our metabolism.
Why is it important to know whether fats are SATURATED or UNSATURATED? Inside each molecule, each carbon atom can establish up to 4 bonds with other atoms (just like a spider with 4 legs could touch other 4 spiders). According to the number of bonds between the carbon atoms, we call fats “saturated” (with no double bonds) or “unsaturated” (with one or more double-bonded carbons in the chain, thus called mono-unsaturated or poly-unsaturated). As a mnemonic, back to my example of the spider, think that if a spider touches four different spiders who tell her four different stories, the poor thing feels overwhelmed with information and thus feels “saturated”.
Saturated fats are abundant in lard and coconut oil; while unsaturated fats are abundant in olives and avocados. Examples of unsaturated fatty acids are palmitoleic acid, oleic acid, myristoleic acid, linoleic acid, and arachidonic acid. These are the substances that are analysed in food quality and food fraud tests.
CIS or TRANS? Unsaturated fats (the ones with double carbon bonds) can also carry the latin prefixes “cis” (“on this side of things”) or “trans” (“on the other side of”), depending on whether their functional groups are rotated in one sense or the other. Back to the metaphors, think of a hand with its fingers pointing in the same direction of the palm (“cis”) or on the opposite (“trans”). “Cis” fats have the functional groups of the molecule on the same side as the carbon atoms, and they are very common in nature. By contrast, “trans” fats have their functional groups on opposing sides of the carbon chain and are rarer in nature.
“Cis” and “trans” molecules often have different properties. In the food industry, this rotation from “cis” towards “trans” transforms oils into margarine, which reacts less with oxygen in the air, becomes less rancid and thus has longer shelf life. This is what you are eating when you ingest “partially hydrogenated oil” as part of snacks and fast food. And here is when you remember having heard about the negative effects of trans fats and their link to coronary artery disease and type 2 diabetes, right?
But hold on there, because there is one last bit of basic fat chemistry that you must know about before we move into discussing their function and properties.
ALPHA or OMEGA? You have also heard us scientists refer to fats with Greek letters, like alpha or omega. This Greek letter alludes to the non-acid end of the fatty acid chain, which is called the omega end. In general, the molecule of a fatty acid is a chain of carbon atoms, with a carboxyl group (–COOH) at the beginning and a methyl group (–CH3) at the end. The Greek letters refer to the relative position of the carbon atoms within the chain: the carbon next to the beginning is labelled as carbon α (alpha), and the carbon next to the end is the ω (omega). And now we add numbers to mark where is the first double-bonded carbon, because this has a great impact on their function in our body. For example, if you read about an omega-3 fatty acid, this means that the third carbon counting from the end happens to be the first one with a double bonded carbon.
Functionally, fats play a key role in our metabolism. Some fats are essential for us to live and yet we cannot synthesize them from other components, so we need to ensure we eat them as part of our diet. The two essential fatty acids for humans are alpha-linolenic acid (ALA, an omega-3 fatty acid) and linoleic acid (LA, an omega-6 fatty acid). And, as I also mentioned at the very beginning, some vitamins are also fats: vitamins A, D, E and K. Thus, it is essential we consume some fats in our diet. Some of the food sources of ω-3 and ω-6 fatty acids are fish, olive oil and walnuts, for instance.
Whenever our metabolism decomposes the fats we ingest, glycerol and fatty acids are released. Glycerol can then go on to be transformed into glucose by the liver and thus become a source of energy. In the absence of glucose, the brain can also function on ketones. This is the rationale for the “keto diet”.
Now you know a bit more about the chemical basis of unsaturated fats like those present in olive oil. Yet there is scientific debate around what kind of unsaturated fats are the healthiest: the mono- or the poly-unsaturated.
Arguably, the reality may lay in striking a correct balance between the quantities we ingest of both of them along with other nutrients, our lifestyle habits and the environmental factors we are exposed to. In this regard, the Mediterranean Diet is the cornerstone of the Mediterranean lifestyle and possibly one of the contributing factors to Spaniards longevity and high quality of life.
Olive oil itself is much more than a compendium of monounsaturated fats. Extra virgin olive oil (EVOO) is a natural juice rich in chlorophylls, carotenoids, phenolic compounds (such as oleocanthal, oleurepein and hydroxytyrosol), flavonoids, coenzymes, antioxidants and many other substances. The levels of these substances vary according to tree type, cultivar, crop stage, year of harvest and other parameters.
Numerous medical studies point at the healthy benefits of consuming extra virgin olive oil, as it seems to reduce the incidence or prevent many cardiovascular, neurodegenerative and inflammatory conditions and even have positive effects when used as part of a therapy.
This is the reason for extra virgin olive oil producers investing so much effort in growing the most resilient and highest yielding tree varieties, protecting them against pests and climate change, harvesting olives at the right ripening time and extracting their juice in the most effective and efficient way possible, so that nutrients are preserved. This laborious process of olive oil production requires tremendous amounts of manpower, dedication and knowledge, fuelled by continuous research and innovation along many fronts.
Therefore, it is important for us all to strike a good balance of nutrients in our diets, and to include a reasonable amount of “healthy fats” such as extra virgin olive oil.