WHAT ARE MEDIUM-CHAIN TRIGLYCERIDES?
Medium-chain triglycerides (MCTs) have become popular among individuals who want to lose weight and among athletes. However, what exactly are MCTs? MCTs are composed of fatty acids that contain between 6 and 12 carbon molecules. We commonly consume foods high in long-chain triglycerides (LCTs) that have more than 12 carbon molecules. Foods high in LCTs include nuts, seeds, avocados, fish, and meat; however, there are only a handful of foods that are high in MCTs (human breast milk, cow’s milk, goat’s milk, coconut oil, palm kernel oil, coconut meat, and dried coconut) (1).
Let me take a step back for a moment to provide a refresher about triglycerides. Triglycerides are composed of a glycerol “backbone” and three fatty acids attached to that glycerol backbone, hence the name “triglycerides” (the scientific and more appropriate name is actually “triacylglycerol”). Furthermore, the fatty acids that make up a triglyceride can be monounsaturated, polyunsaturated, or saturated. The saturation denotes the number of double bonds or “open spaces,” if you will, on each fatty acid. In addition, every fat has some combination of monounsaturated, polyunsaturated, or saturated fatty acid. However, it is the predominant type of fatty acid that defines each type of fat. For example, olive oil has mostly monounsaturated fatty acids, soybean oil has mostly polyunsaturated fatty acids, and butter has mostly saturated fatty acids.
In addition to the saturation of each fatty acid, the length of the fatty acid is also important. There are short-chain, medium-chain, and long-chain fatty acids. MCT oil is made from either coconut oil or palm kernel oil, both of which have high concentrations of MCTs in them. A person can purchase 100% MCT oil, however (2). There are a few more things to note here. First, because MCT oil is made from coconut oil or palm kernel oil, it is primarily a saturated fat (coconut and palm kernel oils are both primarily saturated fats). In addition, MCT oil and coconut oil are not the same thing. Coconut oil is composed of both MCTs and LCTs, whereas pure MCT oil contains just MCTs.
Like many food supplements, MCTs were first used in the clinical nutrition arena. MCTs are used for different types of conditions, in which a person cannot properly digest and absorb short or LCTs. These include individuals with short bowel syndrome, cystic fibrosis, celiac disease, Crohn’s disease, irritable bowel syndrome, and pancreatitis. That is because MCTs are absorbed differently than short-chain triglycerides or LCTs and are transferred directly to the liver to be used for energy. Because MCTs are readily used for energy, it has become prevalent among individuals who would like to lose weight. In addition, it has become popular among athletes.
WHAT DOES THE SCIENCE TELL US ABOUT MCTs?
Wang et al. (3) studied the effects of MCT supplementation in 12-week-old male mice. They randomly assigned the mice either to a regular chow diet or to a regular chow + MCT diet for 21 days. The mice also were exercise trained on a treadmill at both room and high temperatures.
Wang et al. (3) reported that the mice fed the diet with MCT increased mitochondrial biogenesis, especially with higher-temperature exercise. They also reported that MCT did not affect body weight or food intake in high temperatures. Furthermore, they did not report changes in serum glucose or triglyceride concentrations with MCT supplementation. Although these researchers conducted this study in mice, it indicates that MCT may work to upregulate signaling pathways to increase mitochondrial biogenesis. More research is required to evaluate if these results can be replicated in humans.
Mumme and Stonehouse (4) conducted a meta-analysis to evaluate if MCTs can result in weight loss via increased energy expenditure. They compared MCTs with LCTs on weight loss and body composition, as well as blood lipid concentrations. The researchers chose randomized controlled trials that were more than 3 weeks long and conducted in healthy adults. Of the 13 randomized controlled trials that fit their criteria, they reported that MCTs decreased body weight, waist and hip circumferences, total body fat, total subcutaneous fat, and visceral fat significantly better than LCTs. Significant differences in lipid concentrations between MCTs and LCTs were not noted. The researchers also stated that many of the studies varied in dose, duration, and control of energy intake. Mumme and Stonehouse (4) surmised that more research on humans needs to be conducted to more definitively delineate the effectiveness of MCT oil on weight loss and cardiovascular health.
Sung et al. (5) examined the effects of replacing soybean oil with MCT oil on lipid metabolism in 32 rats with type 2 diabetes mellitus. They assigned the rats to one of four groups: low-fat diet + soybean oil, low-fat diet + MCT oil, high-fat diet + soybean oil, and high-fat diet + MCT oil. After 8 weeks, they reported that, in the high-fat diet, MCT oil lowered serum low-density lipoprotein cholesterol (LDL-C), nonesterified fatty acids, and liver total cholesterol concentrations and subsequently increased serum high-density lipoprotein cholesterol (HDL-C) concentrations and the HDL-C/LDL-C ratio compared with soybean oil. In the low-fat diet, MCT oil led to a decreased body weight and increased liver fat oxidation (as measured by enzyme activity).
DO MCTs HAVE ADVERSE EFFECTS?
Overconsumption of any type of fat or one type of food can be harmful to the body. If someone consumed high amounts of MCT oil, it could lead to bloating, diarrhea, abdominal discomfort, and the like. St-Onge et al. (6) did not report adverse effects on the metabolic profile in the 31 women and men in their study who consumed MCT oil. Therefore, if individuals were to incorporate MCTs into their diets, it would be prudent to add small amounts. In addition, individuals need to ensure they obtain the essential fats, linoleic acids, and linolenic acids.
MCTs can certainly have a place in a person’s diet. Whether this leads to increased energy expenditure and weight loss still needs to be confirmed in more studies. In addition, whether MCTs can improve exercise performance through mitochondrial biogenesis also needs to be confirmed. One last point for me to make is this: MCT oil does not have the most inviting flavor, so if you were to add MCT oil to your diet, you may want to do so in smoothies or coffee.
1. United States Department of Agriculture (USDA). US Department of Agriculture Food Data Central [Internet]. 2019 [cited 2019 October 2]. Available from: https://fdc.nal.usda.gov/
2. WebMD. MCT oil: health benefits and common uses [Internet]. [cited 2019 October 2]. Available from: https://www.webmd.com/diet/mct-oil-health-benefits-common-uses#1
3. Wang Y, Liu Z, Han Y, Xu J, Huang W, Li Z. Medium chain triglycerides enhances exercise endurance through the increased mitochondrial biogenesis and metabolism. PLoS One
4. Mumme K, Stonehouse W. Effects of medium-chain triglycerides on weight loss and body composition: a meta-analysis of randomized controlled trials. J Acad Nutr Diet
5. Sung M-H, Liao F-H, Chien Y-W. Medium-chain triglycerides lower blood lipids and body weight in streptozotocin-induced type 2 diabetes rats. Nutrients
6. St-Onge MP, Bosarge A, Goree LLT, Darnell B. Medium chain triglyceride oil consumption as part of a weight loss diet does not lead to an adverse metabolic profile when compared to olive oil. J Am Coll Nutr