​The Difference Between Short-, Medium-, and Long-Chain Fatty Acids

Most dietary fats share the same basic structure: triglycerides – or glycerol molecules bound to three fatty acids. So what is the difference between butter and olive oil or cod liver oil and coconut oil? The answers lie in the structure of the fatty acids that are attached to the glycerol molecule in the fat.
All fatty acids consist of a chain of carbon atoms, which vary in number. The number of carbon atoms in the chain can be as few as four or as many as 30 or more, but the most common lengths in foods are between 18 and 22.
Short-chain fatty acids (SCFAs) have carbon chains that are less than six carbons. SCFAs play a role in some of our most important bodily functions. They supply energy to the cells that line our colon and help keep our gut healthy and strong.
SCFAs help regulate gut barrier function, keeping pathogens and toxins from escaping, while allowing essential nutrients to get where they need to go. The best way to increase our SCFAs is to take a daily prebiotic and probiotic. SCFAs are created when certain probiotics in our gut ferment the prebiotic fiber that exists there.
Medium-chain fatty acids (MCTs) are made from chains of 6-10 carbons. Because they're shorter in length, MCTs are more easily digested than longer-chain fatty acids found in many other foods. MCT oil is typically extracted from coconut or palm oil, and we also get them from dairy products. In fact, more than 50% of the fat in coconut oil comes from MCTs.
One of the benefits of MCTs is a feeling of fullness or satiety. This happens because MCTs increase the levels of two proteins that promote a feeling of fullness: protein YY and Leptin. In one study, those who took an MCT supplement with breakfast ate less at lunchtime. MCTs can also be converted to ketones, which are produced from the breakdown of fat when carb consumption is limited. So MCTs support a keto diet.
Best of all, MCTs boost energy. The body absorbs MCTs more rapidly than long-chain fats, which contain more carbons in their fatty acid chains. Due to their shorter chain length, MCTs travel more quickly from the gut to the liver and do not require bile to break down, like long chain fats. Since MCTs enter our cells without being broken down, they can be used as an immediate source of energy. Taking MCT oil before exercise may help us use more fat instead of carbs for energy.
Long-chain fatty acids are those with 14 or more carbons. They're found in most fats and oils, including olive oil, soybean oil, fish, nuts, avocado, and meat. Saturated long-chain fats are found in dairy fat, coconut oil, palm kernel oil, peanut oil, and other vegetable oils. Monounsaturated long-chain fats are fats found in most animal and vegetable oils, but particularly macadamia, olive, canola, and safflower oil.
Polyunsaturated long-chain fats include linoleic acid, alpha-linolenic acid (ALA), arachidonic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). ALA is a major component of seeds, nuts, and some vegetable oils. Arachidonic is present in meat, eggs, fish, and algae, while EPA is mostly found in oily fish and marine oils. Monounsaturated and polyunsaturated fats are more fluid than the saturated fats and that fluidity supports healthy call membrane function. The relative health benefits of a fatty acid depend more on the sum of all its properties than whether it is short-, medium-, or long-chain.
Some long-chain fatty acids, such as the omega-3 fatty acids ALA, EPA, and DHA, are extremely beneficial to human health. Others, such as the omega-6 arachidonic acid, are essential in small quantities but can be dangerous and pro-inflammatory in larger amounts. 
We have moved beyond the mistaken thinking that prevailed in earlier years, that fats are not good for us. Now we know that the right fats are an essential part of a healthy lifestyle.