Medium-chain fatty acids are naturally occurring fatty acids, consisting of 6-12 carbon atoms. Medium-chain fatty acids  make up around 10% of the fat content of milk and are also found in significant quantities in coconut, coconut oil and palm kernel oil. The conclusion of this study is that a small amount of medium-chain fatty acids in the diet is highly potent in preserving the effect of insulin on the removal of glucose from the bloodstream during high fat intake and energy surplus. The article was published in Diabetes in January 2021.

Medium-chain fatty acids distinguish by being absorbed directly from the gut to the portal vein. This is in contrast to long-chain fatty acids, which occur more frequently in the diet and which, because of their hydrophobic properties, are packed into chylomicrons in the intestinal cells and transported via the lymph to the circulation. The absorption path of medium-chain fatty acids thus goes straight to the liver, and  animal studies show that these fatty acids undergo a high degree of combustion.

Medium-chain fatty acids have been shown in mice and rats to have positive effects on glucose homeostasis during overfeeding with fat. In this study, we therefore wanted to investigate whether medium-chain fatty acids in the diet could have a positive effect on insulin resistance in humans when a hypercaloric, fat-rich diet is consumed.

Two groups of matched young men took part in the trial. Each group consumed, in randomized order, a three-day control diet during which energy balance was maintained, and a three-day hypercaloric fat-rich diet with a 75% energy surplus. The fat-rich diet contained approximately 82E% fat, equivalent to a daily intake of 450 grams of fat.

The main difference between the two fat-rich dietary interventions was the substitution of saturated long-chain fatty acids with ~30 grams of saturated medium-chain fatty acids. The ~30 grams of medium-chain fatty acids stemmed from foods such as coconut, coconut oil, palm kernel oil and dairy products.

The participants in each trial group attended an experimental day on the day after the control diet and again after the hypercaloric fat-rich diet. Insulin sensitivity was measured on the experimental days.

“The data in this study suggest that medium-chain fatty acids have great potential in the regulation of both glucose and fat metabolism and are notable for their availability in common foodstuffs”

After the hypercaloric fat-rich diet with primarily saturated long-chain fatty acids, whole body insulin sensitivity and peripheral insulin-stimulated glucose disposal were reduced by 21% and 26% respectively. Interestingly, insulin sensitivity was unaffected after the hypercaloric fat-rich diet containing ~30 grams of medium-chain fatty acids, despite an average daily energy intake of 21 MJ. With concurrent intake of medium-chain fatty acids, increased fat combustion and increased storage of glucose as glycogen in the muscles were observed.

The study concludes that a small amount of medium-chain fatty acids in the diet is highly potent in preserving the effect of insulin on the removal of glucose from the bloodstream during high fat intake and energy surplus. As a result of these interesting findings, we are now investigating other effects of medium-chain fatty acids in the body, including regulation of energy metabolism, fat combustion and liver-derived molecules. The data in this study suggest that medium-chain fatty acids have great potential in the regulation of both glucose and fat metabolism and are notable for their availability in common foodstuffs.

CONTACT
Andreas M. Fritzen (PhD, Postdoc) and Anne-Marie Lundsgaard (PhD, Postdoc)
Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen

Their email addresses are:
amfritzen@nexs.ku.dk
amlundsgaard@nexs.ku.dk

READ THE ARTICLE HERE
Small Amounts of Dietary Medium-Chain Fatty Acids Protect Against Insulin Resistance During Caloric Excess in Humans  Anne-Marie Lundsgaard, Andreas M. Fritzen, Kim A. Sjøberg, Maximilian Kleinert, Erik A. Richter and Bente Kiens.

Diabetes 2021; 70: 91–98 | https://doi.org/10.2337/db20-0582

Published online: 29 October 2020.