Coconut oil boasts a checkered past. Demonized along with tallow and lard since the 1950’s for high saturated fat content, it’s recently overcome the stigma, and, oddly enough, rocketed to superfood fame. With its unique chemical characteristics, coconut oil has made a comeback as cooking oil, cosmetic ingredient, antimicrobial agent, biofuel, and, according to some, a cure-all medicine.
Is it “pure poison,” as Harvard professor Karin Michels infamously claimed, or the new cure for cancer? Pariah or panacea? Controversy abounds.
Critics love to sling terms like “unsupported” and “unsubstantiated” at the health claims made by coconut enthusiasts. Conversely, ardent marketers (I’m looking at you, Bulletproof) gush about MCT oil as “brain octane oil,” and drop suave lines about MCT metabolites like “TLDR: Ketones give you incredible energy.”
When it comes to coconut oil, hyperbole is hot.
But what does it all mean? Should you be taking MCT oil for weight loss? Is fractionated coconut oil better for cooking or topical applications than the whole oil? What does “MCT” stand for, and what is fractionation, anyway? If you’re confused about coconut oil… join the club.
Don’t worry, we got you. In this article, we’ll clarify the definitions of “fractionated coconut oil” and “MCT” oil. We’ll explore the physiological significance of dietary fats — why we need them and how they’re absorbed and used in the body. Finally, we’ll evaluate the health claims made about coconut oil in its various forms, and dig into why dietary fats are such a fraught topic.
The Chemistry of Fat
First, a quick chemistry primer. I know y’all want to get straight to the point: “is mct oil good for me? Y/N.” Better to know, though, what we’re talking about when arcane clumps of words like “polyunsaturated fatty acids” and “medium-chain triglycerides” start flying around.
Let’s start with triglycerides, the primary constituent of natural fats and oils. Chemically speaking, triglycerides are a type of lipid composed of a glycerol backbone bound to three fatty acid chains. Fatty acids are chains of carbon atoms bonded to hydrogen atoms. Fatty acid chains may be “short” (<6 carbon atoms), “medium” (6-12), or “long” (12+).
Fatty acid chains are either saturated, indicating that each carbon atom is bonded to the maximum number of hydrogen atoms possible, or unsaturated, which denotes the presence of a double bond between carbon atoms. The number of double bonds is delineated by the terms “monounsaturated” (one double bond) and “polyunsaturated” (two to six double bonds).
Unsaturated fatty acids can exist in two forms — cis and trans — which refers to the configuration of atoms at the double bonds. Cis fatty acids are naturally-occurring unsaturated fatty acids, while trans fatty acids are predominantly manufactured by humans via industutrial processes like hydrogenation.
And then there are the essential fatty acids, omega-3 and omega-6 polyunsaturated fatty acids. They’re considered to be “essential” because we require them for specific physiological functions, but the human body is unable to synthesize them on its own. In other words, we must obtain these vital fats from our diet. The numbers three and six denote the positions of the double bonds in the fatty acid chain.
Virgin Coconut Oil
Now that you’ve got a basic grasp of terminology, let’s talk about the chemical properties of coconut oil. “Virgin” coconut oil, abbreviated “VCO,” is typically extracted from dried coconut kernel known as “copra” at low temperatures. It is not refined, bleached, or deodorized. VCO tends to offer a richer coconut-y flavor than refined coconut oil, as well as higher amounts of bioactive polyphenols, vitamin E, and sterols.
Lipid-wise, coconut oil is mostly composed of saturated fat. Medium-chain fatty acid (MCFA) lauric acid (C12) makes up approximately 45-53% of the fatty acid content, while long-chain fatty acid (LCFA) myristic acid (C14) accounts for about 20%. The high saturated fat content of coconut oil renders it solid at room temperature.
Lauric acid, sporting 12 carbon atoms, is right on the edge between medium-chain and long-chain fatty acid. Like other MCTs, the majority of ingested lauric acid is transported directly to the liver where it is rapidly converted to energy and other metabolites, not stored as fat. Lauric acid metabolites include ketone bodies, which can be used by tissues like the brain, heart, and muscle as instant fuel. Of all the fatty acids, lauric acid contributes least to fat accumulation, a property consistent with the observation that coconut oil is a “non-fattening source of energy.”
Coconut oil is, aside from human breast milk, the most significant source of lauric acid in the world.
Lauric acid is lavish with health-promoting effects, notorious for its antimicrobial — antibacterial, antiviral, and antifungal — properties. This fatty acid has also been found to reduce oxidative stress, improve baroreflex sensitivity, and reduce blood pressure in spontaneously hypertensive rats. It was found to exert cardioprotective effects via a mechanism of antioxidant activity.
Fractionated Coconut Oil
Fractionation is a chemical process by which the various types of fatty acids in coconut oil are isolated based on chain length. Fractionated coconut oil is mostly composed of saturated fat rich in medium-chain triglycerides. The high saturated fat content of fractionated coconut oil makes it highly stable and resistant to oxidation.
In the process of fractionation, manufacturers hydrolyze oils to liberate the fatty acids from their glycerol backbone. This can be achieved by acidic hydrolysis, alkaline hydrolysis, or enzymatic hydrolysis with enzymes derived from microbial and animal sources. Enzymatic hydrolysis allows the process to occur under milder temperatures and pH conditions, which prevents unwanted lipid oxidation.
Fatty acids are subsequently distilled to separate them into “fractions” of different fatty acid types. Short- and long-chain fatty acids are removed from the mix, along with the commercially-desirable lauric acid, coveted for medical and industrial purposes.
Importantly, fractionated oils are all refined; they do not occur naturally. Some manufacturers use solvents like hexane, which may leave toxic residues in the finished product, and high temperatures, which can cause the oils to oxidize.
Ultimately, the manufacturing makes the oil.
In their New York Times article “Is Coconut Oil Good or Bad for You?” Rabin and Egan report that refined, bleached, and deodorized coconut oil, which is treated with solvents and subjected to intense heat, “raises cholesterol so reliably that scientists have used it as a control when running experiments on different fats.”
In other words, the type of manufacturing process used can render an oil downright dangerous. Harsh processing may also destroy the beneficial constituents of coconut oil, including antioxidant polyphenols and lauric acid.
Health-conscious companies tend to be more intentional in their fractionation process. Mountain Rose Herbs, for example, reports using a “clean, solvent-free cold-extraction centrifuge process” to produce their fractionated coconut oil.
There are three types of fractionated coconut oil:
- Fractionated coconut oil. The name of this oil is derived from its production process; it’s not necessarily food-grade and is sold for external use in personal care products. Fractionated coconut oil is lighter than VCO and absorbs into the skin more readily, which makes it appealing for topical applications.
- Liquid coconut oil. So-named because the oil is liquid at room temperature due to the removal of long-chain fatty acids. It’s an edible oil typically used for culinary purposes.
- MCT (medium-chain triglyceride) oil. Marketed as a dietary supplement with significant health-promoting properties. MCT oil typically contains only the MCTs caprylic acid (C8) and capric acid (C10).
Fractionated coconut oils contain more saturated fats and medium-chain triglycerides than whole coconut oil, but lack short- and long-chain fatty acids. Fractionated oils have a lower smoke point than whole oils, and should not be used in higher-heat cooking. They also tend to be significantly more expensive than the whole oil — typically double the price.
MCT (medium-chain triglyceride) Oil
First things first: not all MCT oil is exclusively sourced from coconut. Some brands extract their MCTs from a combination of palm kernel and coconut oils, while other brands make a point of using only coconut sources for ecological reasons. For our purposes, we’ll hone in on coconut-derived MCT oil, as it’s the product most likely to be purchased by the conscientious consumer.
MCT oil is lauded by manufacturers as a health supplement that “gives you more energy, better mental performance and fewer cravings.” It’s just now hit the mainstream, but it’s been around since the 1960s. The term “MCT” was coined to describe synthetic triglyceride mixtures made up of mostly caprylic acid and capric acid.
To produce MCT oil, coconut oil was hydrolyzed and fractionated via distillation. Lauric acid, in high demand by the pharmaceutical, surfactant, and cosmetic industries, was removed from the mix. Caprylic and capric acid were then recombined with glycerol to produce the synthetic triglyceride mixture known as MCT oil.
In 1963 a patent was filed to use this oil as a stable liquid vehicle for pharmaceutical products. As MCT oil went into use, people started to notice that MCTs were digested and absorbed differently than fats that contain mostly LCTs. Instead of being absorbed into the lymphatic system, as occurs with LCFAs, MCFAs are absorbed directly into the portal circulation, and head straight for the liver.
Due to this method of absorption and distribution, MCTs were recognized as beneficial for people with impaired fat digestion and absorption. Soon MCTs thrives as a major product for the nutritional management of patients with malabsorption issues. These desirable nutritional effects, as well as its commercial availability, made MCT oil a popular target of clinical research.
In the world of MCTs, not much has changed since the 60s. MCT oil is still manufactured by hydrolyzing coconut oil to separate the fatty acids from their glycerol backbone, then isolating the fatty acids by chain length with a distillation process. Fatty acids are then esterified to convert them back to triglycerides.
Like the original oil, most modern MCT oil contains just caprylic and capric acid. Remember, lauric acid — the dreamboat of the fatty acid family — is conspicuously absent from most MCT oil. Some companies, however, recognizing the benefits of lauric acid, have added it back in, or offer variants of MCT oils that contain specific single medium-chain fatty acids.
MCT Content: Virgin Coconut Oil vs. MCT Oil
Turns out there’s a huge degree of variability, even just between MCT oils, depending on the product. One scientific article reports anything from 4 to 40 grams/liter of MCTs in “selected formulas” of MCT oil.
Another study reported the following concentrations of MCTs in virgin coconut oil vs MCT oil: Organic extra virgin coconut oil (Vita Coco): Lauric acid 48%, caprylic acid 8%, and capric acid 7%. MCT oil (Muscleform): Caproic acid 2%, caprylic acid 50–60%, capric acid 30–45% and lauric acid 3%.
MCT oil is essentially 100% MCTs, while whole coconut oil is about 71% MCTs. Notably, the MCT composition is different. Whole coconut oil contains mostly lauric acid, while MCT oil is largely caprylic and capric acid.
The Function of Fats
Despite the elaborate and ongoing smear campaign against fat consumption, lipids are, in many ways, “the most elemental nutrients for humans.”
Dietary fats serve myriad functions: They’re an energy-dense fuel source, constitute a crucial component of cell membranes, and enable the absorption of dietary fat-soluble vitamins in the intestine. Fats are an essential substrate for the synthesis of metabolically active compounds, including the sex hormones estrogen, progesterone, and testosterone.
The metabolites of lipids also mediate key signaling pathways. Essential fatty acid metabolites, for example, are involved in diverse physiological functions from blood clotting to inflammation to wound healing. Changes in lipid metabolism can affect membrane permeability, disrupt signaling networks, and may be associated with pathological states including cancer, cardiovascular, neurodegenerative, and metabolic diseases, and inflammatory complications.
Absorption and Distribution — Depends on the Fat
First off, the infamous term “saturated fat” is virtually meaningless from a nutritional standpoint. Saturated fat as a dietary category implies that all saturated fats have the same physio-chemical, biochemical, and physiological characteristics. Spoiler alert: They don’t.
Short-, medium-, and long-chain fatty acids all exert wildly divergent physiological actions in terms of how they’re absorbed, distributed, and used by the body. For the purposes of this article, let’s take a look at the differences between absorption and utilisation of long- and medium-chain fatty acids.
We’ll start with the journey taken by long-chain triglycerides (LCTs). As LCTs enter the stomach and duodenum of the small intestine, they stimulate secretion of the enteric hormone cholecystokinin (CCK) and pancreatic enzymes. CCK promotes bile release from the gallbladder to aid in the emulsification of triglycerides into smaller fat droplets to maximize absorption. Pancreatic lipase cleaves fatty acids from their glycerol backbone, releasing them to form micelles, ball-like aggregates of free fatty acids.
Micelles are absorbed into the enterocytes where the fatty acids are converted back to triglycerides and repackaged into small fat molecules known as chylomicrons. These travel through the lymphatic system where they ultimately drain into the subclavian vein to enter the bloodstream. From there they are distributed to the circulatory system, where they can be stored in tissues or metabolized to produce energy.
In order for long-chain fatty acids to be used in energy production, they must be shuttled into the mitochondria by the amino acid derivative carnitine for β-oxidation. In states of carnitine deficiency, such as chronic malabsorption, small bowel obstruction, and starvation, long-chain fatty acids can’t be used efficiently and lead to the build-up of unoxidized fatty acids and the impairment of metabolic processes.
In contrast, medium-chain fatty acids can be absorbed intact across the intestinal barrier. They are shunted directly to the liver via the portal vein, where they are rapidly oxidized to generate energy. In contrast to long-chain fatty acids (LCFAs), medium-chain fatty acids don’t require carnitine to shuttle them to the inner mitochondrial membrane for oxidation. This means that MCFAs are more rapidly absorbed and utilized than LCFAs.,
These divergent pathways for dietary fats serve several purposes. The slow digestion of fat that occurs with LCFAs allows for the gradual release of energy. It also helps the body maximize absorption of fat-soluble vitamins. MCFAs behave like carbohydrates, heading straight to the liver to serve as a rapid energy supply.
Importantly, different types of fatty acids — saturated, monounsaturated, polyunsaturated — can activate different metabolic pathways. Some types of fatty acids may direct metabolic processes towards oxidation (conversion to energy) or storage (which contributes to adiposity). There are also fatty acid-induced differences in satiety and “appetite sensations.”
To be continued……