Fat has long been regarded as the foe of the weight conscious, except for those on a ketogenic diet. The goal for keto diets is to consume enough fat to force the body into ketosis and use fat for fuel instead of carbohydrate (glucose). Can a supplement of a certain type of fat also promote a shift in body composition? Fingers point to MCT (medium chain triglyceride) oil as the magic bullet that can boost metabolism, burn fat and build muscle. 

What a Triglyceride is: Most fats we eat are triglycerides which have three fatty acid chains (if you must know — one attached to each hydrocarbon of a glycerol backbone). Mainly we eat triglycerides with long fatty acid chains (12-18 carbons), which may be saturated or unsaturated. Short chain fatty acids (4 carbons), on the other hand, are predominantly produced by gut bacteria. 

So, what exactly are MCTs? Medium chain fatty acids have 6-10 carbons in length. They are found in coconut (16%) and palm (8%) oils, and to a lesser extent in dairy products. When they are cleaved off and reassembled to glycerol in a lab — Voila! — a medium chain triglyceride (MCT) without long fatty acids is made. So isolated MCT isn’t found in nature but is man-made. MCT oils generally contain either caprylic acid (C8), capric acid (C10) or a combination of the two, and to a lesser extent, caproic acid. 

How They May Be Beneficial

MCTs are metabolized differently than the long chain triglycerides found in most foods. MCTs are digested more rapidly (and transported to liver for oxidation) than long chain triglycerides, which take longer to metabolize and get stored as fat in the process. Providing 10% fewer calories compared to other fats, MCT oil is a lactose-free, gluten-free, vegan, pareve rapid fuel. Weak evidence supports replacement of LCTs with MCTs for promoting weight loss while there’s insufficient research on other metabolic effects and Alzheimer’s disease. 

What are MCT Oil’s Limitations?

Because it’s man-made and lacks long chain fatty acids found in natural foods, MCT oil does not provide essential fatty acids (linoleic an omega-6 fatty acid, linolenic an omega-3). Medium chain fatty acids are always saturated, a concern for cholesterol levels and heart health. Ingestion of large doses of MCT oil may cause significant gastrointestinal distress. As one major manufacturer indicates: “Use of MCT as part of a ketogenic diet requires medical supervision.” Supplementing can get costly with an average MCT oil price of $1 per fluid ounce, compared with coconut oil at 50¢ per fl. oz. 

How Much MCT Oil to Include

Doses of 5 to 48 grams per day (as much as 9 teaspoons) were shown in clinical studies to yield enhanced results. For best tolerance, start with 1 teaspoon (5 mL) 3 to 4 times a day. Slowly (over a week or more), increase to a maximum of 1 Tablespoon (15 mL) 3 to 4 times a day. Food products with MCTs will show “modified coconut and/or palm kernel oil (medium chain triglycerides)” in the ingredients list – check the Nutrition Facts panel for grams of saturated fat. 

Using MCT Oil and Alternative Fats

Don’t take MCT oil on an empty stomach. Like other oils, MCT oil may be mixed into beverages such as juice or milk, or into sauces, salad dressings, and other foods. Colorless, flavorless and odorless, MCT oil is easy to incorporate into dishes but won’t impart more taste. Because of its low smoke point, you shouldn’t cook with MCT oil in high heat. Wholesome fats for Keto diets include coconuts and unrefined coconut oil, avocados and avocado oil, nuts, nut and seed butters, flax seeds, hemp hearts, chia seeds, olives and cold pressed olive oil, cacao nibs, full fat Greek yogurt, fatty fish, whole eggs, butter, and cheese. 

The Bottom Line

For a ketogenic diet that’s already based on an extremely high percentage of calories from fat, substituting MCT oil for other oils in cold food preparation may provide a slight body composition benefit. As an oral supplement, taking undiluted MCTs without food may not be tolerated. You’ll still need to incorporate healthy whole plant fats in your diet for essential fatty acids. 

Sources

1. G Hultin. MCT Oil – Miracle Supplement or Just Another Fad? Food & Nutrition Magazine. Jan/Feb 2016, 5(1): 16. 
2. J Thalheimer. Coconut Oil – What’s Behind its “Health Halo,” and Does the Latest Science Back It Up? Today’s Dietitian. October 2016, 18(10): 32-35. 
3. “Medium Chain Triglycerides (MCT) in Your Diet.” Cdha.nshealth.ca, Capital Health, 2014, www.cdha.nshealth.ca/patientinformation/nshealthnet/0354.pdf. Accessed 9.23.2019 
4. Hill, Ansley. “14 Healthy Fats for the Keto Diet (Plus Some to Limit).” Healthline, 2019, www.healthline.com/nutrition/healthy-fats-for-keto#section15. Accessed 9.17.2019