Coconut oil: What’s in a chain?

Building on my On Nutrition column in Sunday’s Seattle Times, I’m going to talk a little about what coconut oil is made of. The reason for this tropical oil’s purported health benefits is not so much that it comes from a coconut, it’s about the type of fatty acids that coconut oil is made of.
First, what is a fat and what is a fatty acid? The fats that we eat, and that travel in our bloodstream, are called triglycerides. A triglyceride is made up of three fatty acids (tri), joined together by a glycerol backbone (glyceride). All three fatty acids in an individual triglyceride may be the same, or it could contain two of one fatty acid and one of another, or three totally different fatty acids.
All fatty acids start with a chain of carbon atoms. From there, they can be saturated or unsaturated.
  • In saturated fatty acids, all of the carbons are “saturated” with hydrogen atoms. This makes the carbon chains nice and straight, so they can pack in close to each other. This is why saturated fats (coconut oil, butter, bacon drippings, the thick fat around the edges of a steak or roast) are solid at room temperature.
  • Unsaturated fatty acids are missing one or more hydrogen atoms. Wherever a carbon atom has one hydrogen atom instead of two, a bend or kink in the fatty acid chain happens. A monounsaturated fatty acid has one (mono) bend; a polyunsaturated fatty acid has more than one (poly) bends. Because bends happen in different spots on the chain, depending on the type of unsaturated fatty acid, they don’t pack well together, which is why unsaturated fats (vegetable oil, olive oil, other nut and seed oils) are liquid at room temperature.

So, fatty acids have different properties based on:

  • Whether they are saturated or unsaturated
  • Where the bend(s) occur (for unsaturated fatty acids)
  • How long the carbon chain is
Most (85-90 percent) of the fatty acids in coconut oil are saturated. About 45-50 percent of coconut oil is made of lauric acid, a medium-chain fatty acid containing 12 carbon atoms. To compare, the most common saturated fatty acids, palmitic acid and stearic acid, are long-chain fatty acids containing 16 and 18 carbons, respectively. Palmitic acid is found in palm oil and in animal-based fats. Stearic acid is mostly found in animal fats.
The length of the fatty acid chain matters for a variety of reasons that I won’t get into, but the big difference is in how medium-chain and long-chain fatty acids are absorbed. Medium-chain fatty acids are absorbed through the wall of the small intestine and sent directly into the bloodstream. From there, it’s a short ride to the liver, which can use the fatty acids for energy or as building blocks for other fatty acids needed by the body. Long-chain fatty acids, in a nutshell, end up being sent into the lymphatic circulation, packaged into lipoproteins that gradually drop off their fatty acid cargo where it’s needed in the body’s cells and tissues.
It’s this speed of transport and usage by the body that serves as the rational behind claims that coconut oil can aid in weight loss, particularly in the belly area. However, this supposed benefit has only a few short studies with a small number of participants to back it up. It’s interesting stuff, but the notion needs to be tested further with more studies that are well-constructed, last longer and include more people. Coconut oil has been around for a long time, but from a research point of view, it’s still early days.