MEDIUM CHAIN TRIGLYCERIDES AND HEALTH

WHAT ARE MEDIUM-CHAIN TRIGLYCERIDES?
Medium-chain triglycerides (MCTs) have become popular among
individuals who want to lose weight and among athletes. How-
ever, 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 back-
bone, hence the name “triglycerides” (the scientific and more
appropriate name is actually “triacylglycerol”). Furthermore,
the fatty acids that make up a triglyceride can be monounsatu-
rated, 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 mono-
unsaturated, 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, be-
cause 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 syn-
drome, 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. Further-
more, they did not report changes in serum glucose or triglyceride
concentrations with MCT supplementation. Although these re-
searchers conducted this study in mice, it indicates that MCT
may work to upregulate signaling pathways to increase mito-
chondrial 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 cir-
cumferences, 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. Theresearchers 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 con-
ducted 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 con-
centrations and subsequently increased serum high-density lipopro-
tein 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 discom-
fort, 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 in-
corporate MCTs into their diets, it would be prudent to add small amounts. In addition, individuals need to ensure they ob-
tain the essential fats, linoleic acids, and linolenic acids.
SUMMARY
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 bio-
genesis 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.