Medium Chain Triglycerides (a.k.a. MCTs)
Medium Chain Triglycerides, more commonly referred to as MCTs, have made quite a splash in the nutrition world and with good reason—they are pretty amazing fats. To understand what a medium chain triglyceride is, it is helpful to first understand the chemical structure of fats. The fats we find in nature are generally triglycerides, which consist of three fatty acids attached to a glycerol backbone. The fatty acids themselves are chains of carbon atoms varying in length from 4 carbons to 26 or more, commonly classified as short, medium and long chain. In nature the fatty acids that make up a triglyceride are usually a combination of different length fatty acids and not three of the same length. So a naturally occurring triglyceride is some combination of short, medium and long chain fatty acids.*
When we talk about the benefits of MCTs, we are mostly talking about the benefits of the individual medium chain fatty acid tails, or MCFAs, defined as fatty acids that are 6-12 carbons long. These fatty acids are caprioc acid (6 carbons), caprylic acid (8 carbons), capric acid (10 carbons) and lauric acid (12 carbons). There is some debate whether lauric acid is a true medium chain fatty acid, but we’ll cover that more in a minute. MCFAs are unique because they are digested by the body differently than other length fatty acids (such as the omega-3 and -6 fatty acids and oleic acid from olive oil). Their shorter structure makes them easier to break down in the intestines and they require little to no bile. 1 2 Once absorbed, MCFAs are transported directly to the liver, where they are preferentially metabolized to create energy. MCFAs can also easily enter the cells where they fuel energy production. Because medium chain fatty acids are so easily used for energy, they are not readily stored as fat.
While MCFAs are found in many foods, including coconut oil, palm oil, butter, and full-fat dairy (and in particular goat dairy), the amounts available from these foods tend to be pretty low.3 So to concentrate the beneficial MCFAs, manufacturers use a process called fractionation to separate the fatty acids from the glycerol backbone and then recombine them into triglycerides that are comprised only of MCFAs. These are the MCT oils you’ll find on our shelves. Generally the original sources of the MCFAs are coconut and/or palm oils. Caprylic and capric acid are usually the main MCFAs found in MCT oil, and their proportions vary from manufacturer to manufacturer. Caproic acid is usually left out because it has a strong taste and can cause a burning sensation in the throat and stomach.
A word about lauric acid – Although lauric acid has many benefits, its slightly longer chain length (12 carbons) results in it being digested and metabolized a little differently than the shorter MCFAs.4 5 6 It is probably more accurately thought of as an intermediate between the medium- and long-chain fatty acids.7 Lauric acid is highly valued for its antimicrobial properties and does act like an MCT in many ways. Most MCT products do not include lauric acid, but it is abundant in coconut oil for those who wish to include it in their diets. For more information on the benefits of lauric acid, please see the Natural Grocers’ Customer Literature File “Coconut—Health Benefits”.
Because MCTs are so easily absorbed, they have been used clinically since the 1950s in cases of pancreatic insufficiency, fat malabsorption and in total parenteral nutrition. Later MCTs were added to preterm infant formulas. More recently, MCTs have drawn the attention of athletes and those looking to enhance their production of ketones. Including MCTs in the diet may support the following health goals. * For a more detailed look at the chemistry of fats and in particular the differences between poly, mono and fully saturated fats, please see the Natural Grocers’ Customer Literature File “Fats”.
Ketones are an alternative energy source produced by the liver from fatty acids. Ketones are normally produced in small amounts when there is a lack of glucose to supply energy, such as during extended exercise or during an overnight fast. If glucose supplies remain low due to low carbohydrate intake or fasting, the body will increase its production of ketones. Ketones are especially important because they supply an energy source for the cells of the central nervous system, including the brain, which, unlike most other cells, cannot use fatty acids to produce energy. In addition to being used for energy, ketones have signaling functions that positively regulate genes related to aging, oxidative stress and healthy sympathetic nervous system activity.8 9 MCTs are converted to ketones in the liver, even in the presence of some glucose, which means they provide ketones and the benefits that come from them, without the need for a very-low carbohydrate diet.10 Although the rise in blood ketone levels from MCT supplementation alone is much less dramatic than the rise seen on a ketogenic diet, one small human study estimated that daily MCT supplementation could supply ketones to contribute 8% to 9% of brain energy.11 The shorter the medium chain fatty acid, the more quickly and fully it can be converted to ketones, so caproic acid is converted the quickest and lauric acid the slowest.12 13 Conditions that may benefit from enhanced ketone production include epilepsy, cancer and impaired neurological function. For more information on ketones, please see the Natural Grocers’ Customer Literature File “Ketogenic Diet”
MCTs are readily converted to ketone bodies in the liver and these ketones can be used as an alternative fuel source for the brain, which many claim enhances their focus and mental function.
Decreased utilization of glucose is an early symptom in the brains of Alzheimer’s patients, often occurring long before more noticeable symptoms occur.14 Although the brain begins to lose its ability to use glucose for fuel, its ability to use ketones remains normal.15 Not only do ketones act as an alternative fuel source for brain cells, they may also aid in the production of acetylcholine, a neurotransmitter necessary for processing memory and learning, which drops in patients with Alzheimer’s disease.16 17 Several studies have shown improved cognition in those with mild-to-moderate cognitive decline after MCT supplementation, although the benefit is most pronounced in those who do not carry the APOE e4 gene variant that is associated with an increased risk of Alzheimer’s disease.18 19 20
Because MCTs enhance energy expenditure and may have a satiating effect, they are often promoted for weight loss.2122 23 24 25 26 Most human studies have found that replacing a portion of dietary long-chain fats with MCTs leads to modest body weight and body fat loss.27 28 The effect appears to be greatest in overweight and obese subjects.29
The research using MCTs to enhance athletic performance in trained athletes has been mixed, with some studies showing slight improvements and others showing no improvement.30 31 32 33 One study conducted on recreational athletes found that 6 grams of MCT oil daily for two weeks improved perceived exertion during moderate intensity exercise and extended the duration of high-intensity exercise while suppressing blood lactate concentrations.34
Although lauric acid tends to get most the antimicrobial praise, the other MCTs also appear to be capable of fighting pathogenic bacteria and fungi, including Candida albicans and Chlamydia trachomatis. 35 36 37
Coconut oil is a good source of MCTs, but it depends on which MCTs you’re after as to whether it is the best source for you. About 65% of the fat in coconut oil is MCTs, and of that, lauric acid makes up about 75%, with 8% caprylic and 7% capric.38 Lauric acid produces a delayed and less prominent rise in ketones, compared to other, shorter MCTs, but it is strongly antimicrobial.39 To get the same amount of the shorter chain MCTs found in one tablespoon of MCT oil (about 14 grams) you would have to eat almost nine tablespoons of coconut oil.40
MCT oil has a very mild taste and can easily be added to the diet in many ways. Probably the most popular way is to add MCT oil to your morning coffee. (Check out our Hacked Coffee recipe at https://www.naturalgrocers.com/recipe/hacked-coffee/.) Outside of coffee, MCT oil can be added to smoothies, used to make salad dressing or as a finishing oil for cooked foods. In general avoid heating MCT oil, since it has a low smoke point and when exposed to temperatures over 300°- 320°F it can oxidize (a.k.a. go rancid).41 42
High levels of MCTs both short- and long-term have been found to be safe in a variety of animals. Human studies have used anywhere from 6 to 30 grams of MCTs per day and up to 1 gram per kilogram of body weight has been found safe (that’s about 68 grams per day for a 150 pound adult). 43 The most common side effects are diarrhea, upset stomach, and intestinal gas. Less common side effects include anxiety, reduced appetite, dizziness and headaches. Most side-effects can be avoided by starting with a very low dose of MCTs, such as a half or one teaspoon a day, and slowly working your way up to a full dose, allowing your body time to adjust.