Fats: what are fats and how do they work?

Geschatte leestijd: 26 minuten Fats in general have a bad reputation when it comes to losing weight. In this article, we delve into the role of MCT fats and their effects on fitness and weight loss. MCT stands for Medium Chain Triglyceride, a type of fat with unique properties. MCT oil is said to provide extra energy because fewer carbohydrates are burned while more fats are burned. So, you would lose weight faster by using MCTs.

Losing Weight with Saturated Fats

By sparing glycogen in the muscles, they would become less quickly depleted, meaning proteins are not or less quickly broken down, and thus there is less muscle breakdown. It would therefore be the ideal addition to the diet of anyone who wants to lose weight, but also of bodybuilders who need extra calories for muscle mass but do not want these to result in more body fat. Now you can immediately purchase a bottle and, just like in the past, have the whole family line up for a spoonful of MCTs instead of cod liver oil. Personally, I always find it handy to know how and why something works before I give in to the umpteenth hype. Given that the word “would” occurs quite often in this introduction, it will not surprise you that, when tested, some of these claims have not been proven in practice or have even been debunked. MCTs appear from most studies to lead to more fat burning, reduced appetite, and weight loss. The supposed saving of glycogen and less muscle breakdown, however, seem to be controversial.

What are MCTs?

Saturated fats in food have a bad reputation. They are said to be unhealthy and lead to a higher risk of heart diseases (1 Hu). For this reason, it is often advised to limit the amount of saturated fats in the diet (2 Lichtenstein). However, not all fats are the same. MCT stands for Medium Chain Triglyceride. Other names are MCFA (Medium Chain Fatty Acid) or in Dutch MKVZ (Middellange Keten Vetzuren). MCTs are “fatty acid esters” of glycerol (also called: glycerine). This means they consist of glycerol with fatty acid chains attached. Triglycerides refers to the fact that there are three fatty acid chains connected to the glycerol. Triglycerides are the main components of animal fats and vegetable oils. The fats in food consist of about 95% triglycerides (3 Whitney) In the image above (figure 1) you see the structural formulas, that is, a schematic representation of how the molecules are built up. You see a glycerol molecule on the left and a “free fatty acid” on the right. This fatty acid contains 12 carbon atoms. At every place where two lines meet or end and no atom or connection is mentioned, is a carbon atom (“C”. These are often not shown in structural formulas for readability). At the bottom right in figure 1 you see a triglyceride, namely glycerol with three fatty acid chains. Fatty acids can occur with a minimum of 2 carbon atoms and a maximum of 22. Most natural fatty acids contain 12 to 18 carbon atoms. MCTs differ from the more common long-chain fatty acids (LCTs) in that two or three of the fatty acid chains are “medium-length”. The length of a fatty acid chain is determined by the number of carbon atoms. In this way, fats (or fatty acids) can be divided into:

• Short chains: 6 or fewer carbon atoms
• Medium chains: 6-10 carbon atoms
• Long chains: 10 or more carbon atoms

Next to this, you see different lengths of fatty acid chains ranging from short to long chains. If you look back at figure 1 and count the number of carbon atoms, you see that it is a long chain with 12 carbon atoms. Depending on the length of the chain, these fats are processed differently during digestion and metabolism (4 Babayan). Most studies that have shown the dangers of saturated fats have mainly looked at long-chain fatty acids.

Sources of MCTs

MCTs are found in nature in the largest amounts in coconuts. Coconuts consist of about 86% saturated fats. Of these, 68% are made up by MCTs. Other sources are palm kernel oil and dairy, albeit in smaller amounts. In the 1950s, MCTs were first synthesized from coconut oil by a researcher from Harvard, Vigen Babayan (5 Kaunitz 58). This has the great advantage that it is easier to replace long-chain fatty acids with medium-chain fatty acids because natural coconut oil contains both long and medium chains.

Differences in Metabolism of Medium and Long Chain Fatty Acids

Medium and long-chain fatty acids not only deliver different amounts of energy, but also work according to entirely different paths during digestion. It is often heard that proteins and carbohydrates yield 4 calories per gram and long-chain 9 calories per gram. However, the latter concerns long-chain fatty acids. Medium-chain fatty acids yield about 10% fewer calories, namely 8.3 per gram (6 Kaunitz71). However, that is not the most important difference. In short: MCTs are absorbed and burned faster than LCTs, making them more efficient as fuel and leaving less to be stored as body fat (7,8,9,10,11 St-Onge 2x 2003 and 2002, Nosaka, Tsuji). For understanding, it is good to look at the differences between MCTs and LCTs in two ways:

• The speed at which they are processed by the stomach and intestines and absorbed into the bloodstream (digestion)
• The way they, once arrived at the cells, provide energy (metabolism)

Differences in Digestion vs. Metabolism in Short Digestion and metabolism are often confused or seen as the same. This is incorrect. When you eat something, digestion comes first. This is, in short, the processing of the food you have taken into nutrients that can be absorbed into the bloodstream. The metabolism (or “metabolism”) is the whole of anabolic (building) and catabolic (breaking down) processes in cells and organisms. The metabolism makes use of, among other things, the substances that digestion provides. Digestion of Long Chain Fatty Acids After leaving the stomach, the long-chain fatty acids enter the small intestine. When this happens, the release of the hormone cholecystokinin is stimulated. This hormone gives the order to the gallbladder to produce bile and release it to the small intestine. The bile ensures that the fat is divided into small droplets (emulsification). The pancreas then secretes lipase. Lipase is an enzyme that ensures that the triglycerides are broken down into monoglycerides (glycerol with one fatty acid tail) and 2 free fatty acids. Together with bile (salt), these monoglycerides and fatty acids form so-called micelles. Cholesterol is added to these micelles in the cells of the intestinal wall (enterocytes) to form chylomicrons. Only as chylomicrons can LCTs pass through the intestinal wall. They eventually enter the blood and thus into the liver, which further breaks them down. Eventually, the fats provide energy to the cell in this way, but they can also be released to fat cells (12,13 St-Onge 2002, Hyson) The above process of all steps that LCTs must go through explains why these long-chain fatty acids are effective in storing energy (after all, twice as many calories per gram as carbohydrates and proteins), but not in quickly providing energy. Before the energy is available, the long-chain fatty acids must be processed for six to eight hours.

Digestion of Medium Chain Fatty Acids

However, MCTs are not first emulsified, split, converted into micelles, and chylomicrons. For MCTs, this trajectory is much shorter and more direct. After passing through the stomach and absorption by the intestine, they immediately enter the blood. As a result, they provide energy quickly like carbohydrates and almost nothing is stored as fat. In cells, they pass the wall to the mitochondria (powerhouses of the cell) very quickly, but then we are already in the area of metabolism.

Difference in Metabolism between MCTs and LCTs: Speed of Fat Burning

Once arrived via the blood at the cells where they need to provide energy, the way MCTs and LCTs do their work on the spot also differs. The energy in the (muscle) cell is provided by burning (oxidation and breakdown). This happens in the power plant of the cell, the mitochondrion. To supply it with energy, they must first reach it. LCTs cannot pass the inner membrane (as it were, the wall) without the help of carnitine produced by the body. Carnitine is composed in the liver and kidneys from the amino acids lysine and methionine. MCTs can pass this membrane directly and are therefore, once arrived at the cell, faster in their action. Once arrived in the mitochondrion, the fatty acids are further broken down into acetyl CoA molecules. These are then further broken down in the so-called citric acid cycle (or Krebs cycle) into the energy carriers ATP and ketones.

Positive Effects of MCTs on Weight and Body Fat in Theory

Nice story, but ultimately you want to know what practical benefits you have from it. MCTs are said to have several advantages due to their direct action:

• Less fat storage
• Higher fat burning
• Sparing of glycogen
• Higher total energy expenditure (yago-aryedi)
• Lowering appetite

There have been various studies that have looked at how far these benefits could be demonstrated in practice.

Positive Effects of MCTs on Weight and Body Fat as Shown in Studies

There have been multiple studies on the effects of MCTs on body composition. Most of them show that MCTs reduce both body fat and total weight.

Consumption of MCT oil as part of a weight-loss plan improves weight loss compared with olive oil and can thus be successfully included in a weight-loss diet. Small changes in the quality of fat intake can therefore be useful to enhance weight loss. Marie St. Onge

According to the opinion of a researcher who has conducted various studies on this (14 St-Onge 2008). However, multiple studies have been conducted that do not all show the same results. Her own various studies have also yielded different results. You may find this confusing, but just the different circumstances under which the study was conducted (type of subjects, amounts used, measurement methods, etc.) can often provide additional insight. Instead of going into all these studies in detail, I have made an overview with different studies and outcomes (7,8,9,11,13,14,15,16,17). There are studies that also looked at the feeling of satiety and hunger. I have not included these unless they also measured the ultimate effects on weight and body fat. Most studies show a positive effect. There are two that see no differences, but both have compared MCTs with the use of other means (olive oil and hydroxycitric acid). In those cases, it is questionable to what extent both means influence each other’s effect. The latter is also important when MCTs and LCTs are mixed, but more on that later. In addition, it is noticeable that in the study by Tsuji et al. (11), it was found that men with a BMI higher than 23 lost more weight and body fat than men with a lower BMI. In the study by St-Onge and Jones (8), this is just the opposite. They also note:

Furthermore, MCT consumption may stimulate EE and fat oxidation to a lower extent in men of greater BW compared to men of lower BW, indicative of the lower responsiveness to a rapidly oxidized fat by overweight men. -St-Onge, McGill University, Montreal, Quebec

Other researchers have specifically looked at this difference to determine whether a higher weight has a positive or negative effect on the action of MCTs (18). The researchers from the University of Naples had 6 slim men and 6 overweight men as subjects. They measured the so-called postprandial thermogenesis, the heat generated by metabolism after eating a meal as an indication of the speed of metabolism. The meals themselves consisted of: Either 38 grams of LCTs, or 30 grams of MCTs plus 8 grams of LCTs. They saw that the metabolism of overweight men was increased more than that of slim men. The difference was not statistically significant (P<0.05). They take into account the possibility that this difference could be significant if more men participated in the study. In addition, they point to individual differences in the way metabolism normally responds to LCTs.

MCT-induced thermogenesis tended to be higher in obese individuals than in lean ones…… …..This very preliminary observation raises the hypothesis that MCT-induced thermogenesis is not decreased in those obese subjects who exhibit a blunted thermic response to a conventional LCT-mixed meal. – L. Scalfi, University of Naples

Reduced Appetite Due to MCTs

Do you know that feeling? You go to McDonald’s with huge hunger. You order a Big Mac menu, large of course, with cola and fries sauce and start eating. Halfway through the meal, you are full and drive home, but hardly there you are hungry again. There are studies that showed that fats (in general) lead to less satiation (over a short period) and thereby cause people to eat more (19, 20 Lissner). In one study, eating carbohydrates resulted in no hunger one and a half hours later while the same amount (in kcal) of fat did not seem to suppress appetite at all (19 Blundell). However, these studies mainly used LCTs as a representation of the fats that people mainly eat. Intake of MCTs does result in reduced appetite in the hours that follow. The extent to which a meal provides satiation and how long it takes before you get hungry again have an impact on the total amount of food most people consume. Many people let the amount and frequency of meals depend on their feeling of hunger. When following a diet, this can be different when you crave a certain type of or amount of food, but do not give in to stick to your diet. It would also be easier if your stomach did not scream for those carbohydrates that you have reduced in your diet, for example. Several studies show that MCTs would be a successful aid in losing weight because they provide more and longer-lasting satiation. In the image above, you see how much is eaten one and a half and three and a half hours after intake of carbohydrates (sucrose and starch), protein (albumin), fats (kaolin,oil), water, or nothing (sham) (21 Geliebter). You see in the chart that intake of (LCT-)fats almost suppresses appetite as little as drinking water or eating nothing. The tricky part with these different studies, however, is that they have used many different types of fats, which makes comparison difficult (22 Samra).

Relatively few studies have investigated the responses of specific fats and fatty acids on food intake. Furthermore, studies have used different fats and fatty acids making it almost impossible to draw conclusions. However, it is clear that not all fats are equal in their effect on appetite and associated biological processes. – Rania Abou Samra. “Fat Detection: Taste, Texture, and Post Ingestive Effects.”

As said, not all fats are the same. When comparing the influence on appetite of LCTs and MCTs, MCTs appear to lower appetite more (23 Stubbs, 24 Friedman, 25, 26 Wymelbeke 98 and 01).

Hunger may be delayed and food intake reduced under metabolic conditions that spare carbohydrate oxidation, especially during oxidation of medium-chain triacylglycerols (MCTs) or monounsaturated triacylglycerols.(1998) Carbohydrate may have a greater role in the duration of satiety than does fat, but MCTs may play an active role in other aspects of the control of food intake, especially in satiation at the next meal.(2001) -Van Wymelbeke, Institut Européen des Sciences du Goût et des Comportements Alimentaires

MCTs are thus handy if you are losing weight or cutting and get that empty, weak feeling from hunger due to low intake of carbohydrates. It is disadvantageous if you take them as extra fats to increase your total calorie intake when you actually want to gain weight. For ectomorphs who have difficulty gaining weight, this can be a disadvantage. On the other hand, MCTs are a very easy way for “ectos” to increase calorie intake. Swallowing two tablespoons of MCTs provides 30 X 8.3 = 249 kcal. That’s almost as much as, for example, 4 boiled eggs or 3 slices of whole wheat bread.

MCTs Against Muscle Breakdown: “Sparing Glycogen”

An extra reason why MCTs would be interesting for bodybuilders and strength athletes is the suspicion that the direct energy MCTs can provide would ensure that glycogen (normally the main supplier of energy, stored in muscles and liver) can be spared. When this fuel is depleted and there is still a need for energy (initially for the brain, but also when further training), the body switches to catabolic mode. Instead of nutrients from food being used to build tissue and provide energy, tissue such as muscles and fats are now broken down to provide energy. This leads to muscle breakdown that could be prevented if the glycogen supply (converted from eaten carbohydrates) was not depleted. MCTs would provide this sparing. These are at least the claims in the promotional texts for bottles of MCT oil. Research shows that this claim about sparing glycogen does not quite hold up. Most studies on this show, in fact, that glycogen is not spared by intake of MCTs. To keep a long story short, I will refer to the review that a researcher from Oxford did after studying 17 studies in this area (27 Clegg). Of the 11 studies that looked at carbohydrate/glycogen burning, there were as many as 8 that saw no positive effect of MCTs, 2 that did see this and one that saw a negative effect. Also, the positive influence on performance that this supposed sparing of glycogen would entail, could not be demonstrated in these studies.

Results indicate that MCT feeding is ineffective in improving exercise performance and future work should focus on the health benefits and applications of MCT. – M.E. Clegg, Functional Food Centre, School of Life Sciences, Oxford Brookes University

Researchers from the University of Texas (28 Horowitz) looked at the amount of glycogen in the muscles and how much of it was left after intensive exercise. In addition, they looked at the amount of glucose in the blood at rest (glucose can be stored by the muscles as glycogen). They saw no difference in the amount of glycogen after exercise when carbohydrates with MCTs had been taken beforehand instead of only carbohydrates. They did see that after taking carbohydrates with about 25 grams of MCTs, the amount of glucose in the blood was higher (say “more in the reserve tank”), but during exercise, this did not lead to more glycogen in the muscles.

Therefore, the addition of a small amount of MCT to a preexercise CHO meal did not reduce muscle glycogen oxidation during high-intensity exercise, but it did increase glucose uptake at rest. – J. F. Horowitz, University of Texas

A lot of research has also been done on this at the University of Limburg. In Maastricht, researchers looked at it in a different way in 1996 (29 Jeukendrup 96 Mar). They looked at the extent to which MCTs contributed to the total consumed energy during intensive exercise. They also looked at the difference in contribution when the glycogen supply was depleted beforehand and when it was filled. They saw that when glycogen was depleted beforehand, more already present fat was burned, but the burning of ingested MCTs did not increase. It seems therefore not as if the muscles burn more MCTs when the glycogen reserves are empty. Moreover, the total contribution to consumed energy by MCTs was limited, namely 6.5 to 7.6 percent. According to them, this also has to do with the limited amount of MCTs that can be taken without causing stomach problems (30 Jeukendrup 98).

We conclude that 1) the contribution of MCT to total energy expenditure was small and 2) strenuous exercise the day before the experiment, followed by a low CHO intake and leading to a low CHO availability, substantially increased total fat oxidation but did not significantly increase MCT oxidation. – A.E. Jeukendrup, University of Maastricht

In another study by the same researchers, they looked at whether there was a difference in glycogen consumption when only carbohydrates were eaten before the exercise or carbohydrates with 29 grams of MCTs (31 Jeukendrup 96 Jul). They saw no difference in consumed glycogen after the exercises (180 minutes of aerobic at 50% Wmax). However, they did see a larger amount of ketone bodies after taking MCTs (see further).

It is concluded that 29 g MCT co-ingested with CHO during 180 minutes of exercise does not influence CHO utilization or glycogen breakdown. – A.E. Jeukendrup, University of Maastricht

On the other hand, there are also some studies that did find a sparing of glycogen. South African researchers gave subjects, prior to three hours of cycling, carbohydrates, MCTs, or MCTs and carbohydrates (32 van Zijl). They did find that the oxidation (burning with the help of oxygen) of glycogen, especially the first two hours, was lower when MCTs or a combination of MCTs with carbohydrates had been taken. They therefore conclude:

These data suggest that MCT oxidation decreased the direct and/or indirect (via lactate) oxidation of muscle glycogen. – Van Zijl, University of Cape Town Medical School

The glycogen-sparing effect is therefore controversial. Moreover, a possible contribution of MCTs is limited to 7 to 13 percent of the used energy due to the amount of MCTs that can be processed at one time by the stomach and intestines without causing stomach problems (30, 33 Jeukendrup 95, 34 Philiposian). If this effect exists, it is limited.

“MCTs Do Not Spare Glycogen, But Limit Muscle Breakdown Through Ketone Bodies?”

Not really convincing evidence of spared glycogen reserves. This does not take away that MCTs can theoretically limit muscle breakdown. The glycogen reserves are depleted just as quickly, but MCTs may allow the body to switch more quickly to burning body fat for energy and thus limit the breakdown of muscle protein. When the primary fuel glycogen is depleted, the body can switch to burning fats (lipolysis) and/or breaking down muscle protein into peptides and amino acids (proteolysis) to create new glucose (gluconeogenesis) that can again be stored and used as glycogen. Stored (free) fatty acids can then serve directly as fuel for muscles, but not for the brain. For this, ketone bodies (or ketones) are needed (35 Owen). These ketone bodies can also be used by the muscles. Ketone bodies are produced in the liver from the burning of fatty acids and thus contribute to increased fat burning. This ensures that more fatty acids serve as fuel, thus limiting the breakdown of proteins (from which the muscles are built) (36 Sherwin). This can also explain the difference in effectiveness with depleted or full glycogen reserves as shown by the researchers from Limburg (29 Jeukendrup 96 Mar). This made no difference in the burning of the ingested MCTs, but did for the burning of stored fats. Since the glycogen reserve was depleted in one case, ketone bodies were produced that increased fat burning. The number of ketone bodies was higher when, in addition to carbohydrates, MCTs were also taken (29, 31 Jeukendrup 96 2x). The number of ketone bodies increases and with it the burning of fat. However, this does not seem to have an effect on the breakdown of protein as, for example, shown in the following two studies.

MCTs Do Not Always Limit Muscle Breakdown

Instead of measuring whether glycogen is spared, it may be more useful to look directly at the influence on muscle mass. French researchers did this with so-called isotope labeling where labeled leucine (amino acid) was introduced and followed to measure muscle breakdown (37 Liet). When babies are born prematurely, the challenge is to increase their weight as quickly as possible. Muscle growth and preventing breakdown contribute to this. Muscle growth is, after all, the result of the continuous, complex battle between muscle breakdown and the buildup of muscle mass (38 Sheffield 2004). To see if MCTs help better, they compared the influence on muscle breakdown by administering a 50/50 mix of MCTs & LCTs with only administering LCTs. Contrary to what you might expect after the story told above, muscle breakdown was greater when the mix of MCTs with LCTs was administered.

Mixed MCTs may not be as effective as LCT-containing emulsions in promoting protein accretion in parenterally fed preterm neonates. -Jean-Michel Liet, Centre de Recherche en Nutrition Humaine

Ok, but what about adults? French researchers had 31 healthy men aged 23-32 as subjects. They gave (39 Beaufrere):

• LCTs, or
• 50/50 mix of LCTs/MCTs
• β-hydroxybutyrate (ketone bodies)
• Saline (salt solution)

Convenient that they also looked at the effect of directly administered ketone bodies. The researchers saw, however, that neither MCTs nor ketone bodies had a protein-sparing effect while LCTs did. They find this remarkable since you would expect that MCTs, whether or not through the production of ketone bodies, would actually limit muscle breakdown.

Therefore, 1) the effect of fatty acids on amino acid oxidation is not mediated by ketone bodies, 2) it depends on the fatty acid chain length, 3) long-chain fatty acids but not medium-chain fatty acids could play a protein-sparing role during parenteral nutrition. – B. Beaufrere, Institut National de la Sante et de la Recherche Medicale

It has not been proven that MCTs actually limit muscle breakdown. Remarkably, I also find that by mixing MCTs with LCTs, the muscle-sparing effect of LCTs is apparently negated. This may mean that there were too few LCTs taken for the sparing effect when half was replaced by MCTs. They received a total of only 0.15 grams of fats per kilogram of body weight. For a person of 80kg, this is only 12 grams of fats. In the case of the mix, therefore, only 6 grams of LCTs. Another possibility is that the metabolism of LCTs proceeds differently when they are taken together with MCTs. However, the following piece shows the opposite.

MCTs vs. LCTs: Competitive Effects of LCTs on the Metabolism of MCTs

The tricky part with some of the above studies is that MCTs and LCTs were administered together in one meal. MCTs and LCTs work competitively with each other within metabolism. This ensures that some effects of MCTs are negated while others, strangely enough, are actually strengthened (40 Cotter et al. 89). American researchers compared the effect on various values in the body of dogs such as insulin, the amount of MCFA’s or MCFFA (Medium Chain Free Fatty Acids), and the number of ketone bodies. They saw that the number of MCFFA’s, the form in which MCTs ultimately do their work, such as the production of ketone bodies, was smaller if LCTs were also administered next to MCTs. The highest line in the graph on the left is that in which the dogs were given 3 grams of MCTs per kilogram of body weight. The two lines below are, respectively, with the addition of 3 grams and 1.5 grams LCTs per kilogram of body weight (the bottom line is from the control group that received a salt solution). The LCTs thus ensure that fewer MCFA’s are available from the MCTs to do their work, such as the production of ketone bodies. Just that last one makes it remarkable that when LCTs were administered, the number of ketone bodies increased (table below). You see in the table below the differences. Even if the numbers mean nothing to you, it is clear that the number of ketone bodies after, for example, 2 hours was twice as high when, in addition to MCTs (group 1), 1.5g/kg of LCTs were also added (group 2) and even three times as high when 3 grams per kilo of LCTs were added (group 3). Group 4 was also the control group that received a salt solution here. The researchers suspect that this may be because the MCTs cannot do their work due to “competition” from LCTs in the muscles and therefore become more active in other places such as the liver.

The possible explanation for this increase may be a shift in MCT metabolism away from peripheral sites (such as muscle) to visceral sites (such as liver) in response to LCT competition for the peripheral sites. – R. Cotter, Baxter Healthcare Corporation

If MCTs are not directly used as fuel and thus do not spare glycogen, leading to less muscle breakdown, the only benefit left is a reduced appetite and increased fat burning. The increased fat burning is attributed to a greater number of ketone bodies. If a higher number of ketone bodies and thus fat burning is the only advantage, you might be inclined to think that you should therefore better mix MCTs with LCTs because this leads to a higher number of ketone bodies. In the studies mentioned above in the overview of studies that looked at weight loss, there are a few where different ratios of MCTs and LCTs can be compared. However, it is very difficult to draw a clear conclusion from this. In some cases, only MCTs turned out to mean more weight loss than together with LCTs (18 Scalfi). In that case, however, 30 grams of MCTs were mixed with 8 grams of LCTs. In the study that shows that MCTs together with LCTs lead to more ketone bodies, at least half of the amount of MCTs was given as LCTs or the same amount. Research that looks at multiple ratios and the effect on weight and body compositions might provide an answer.

How to Use MCTs?

Now, the fact that you burn fat faster and lose weight may be enough to decide to buy MCTs, regardless of all claims that have been proven otherwise. Then the question is how you use them. In this respect, you can ask yourself two questions:

• How much should I take?
• When should I take it?

Dosage of MCTs

In this respect, you can ask yourself how much MCTs your body can convert at most. However, that question is not very relevant because you will likely be vomiting on the ground and/or have diarrhea (possibly an indication of the liver’s inability to process that large amount?) long before you have taken that amount of MCTs. In many of the research texts, you can read that the subjects were given as large a dose as is known not to cause stomach problems. How much you can take is therefore partly personal and a matter of getting used to. The previously mentioned researchers from Limburg, for example, saw that performance decreased when 85 grams of MCTs had been taken beforehand (30). They attribute this negative influence on performance to stomach problems caused by this high intake at once.

The negative effect of MCT ingestion was associated with increased gastrointestinal complaints (ie, intestinal cramping). These data suggest that large amounts of MCTs (85 g) ingested during prolonged submaximal exercise may provoke gastrointestinal problems leading to decreased exercise performance. – A.E. Jeukendrup, University of Maastricht

Research has been conducted on the possible side effects of MCTs on, among other things, liver functions, various types of cholesterol, and the amount of triglycerides in the blood. A study in Japan showed that intake of 40 grams per day had no adverse effects on all these values (41 Nosaka). This study was, however, conducted by Nisshin Oil, a major producer of MCTs. In animal experiments (rabbits and rats, pigs), amounts of more than 9 grams per kilogram of body weight have been administered. For a human of 80 kilograms, this would mean an intake of 720 grams. Such amounts have not been tested on humans and would also be absurd since you would then almost reach 6000 kcal per day just from MCTs! It is more useful to look at how many fats your diet should consist of (often advice is to get 20 to 25 percent of total calorie needs from fats). Suppose you need to get a total of 4000 kcal, of which you want to get 1000 kcal from fats. You can then choose to get at most up to half from MCTs. You then come to 500 / 8.3 (number of kcal that MCTs per gram yield) = 60 grams. Most manufacturers recommend between 30 and 45 grams per gram. The maximum amount of MCTs that the gastrointestinal tract can process at one time is 30 grams per three hours (33 Jeukendrup 95). It therefore makes no sense to take more than 30 grams of MCTs in less than 3 hours (about two tablespoons). Getting half of your fats from MCTs seems like a lot, but is not unusual. In Sri Lanka, fats are mainly obtained from coconut oil, which, as mentioned above, consists of 68% MCTs. From the UN Demographic Yearbook (1978), it appeared that Sri Lanka had the lowest death rate from ischemic heart diseases (caused by insufficient blood supply to the heart) (42 Kaunitz 86). Namely 1 per 1 million inhabitants instead of 38 to 188 per 1 million as in most countries. This low figure is very likely caused by the lowering effect that MCTs seem to have on cholesterol (42 Kaunitz 86). In practice, several experience some stomach discomfort or nausea, especially when taken on an empty stomach. There are various tips to prevent this, such as taking the MCTs with a meal. Thus, there are many who add the MCT oil to a protein shake, but also tea and even coffee. MCT oil is also great for salad dressing. In addition, you can also gradually increase the dosage to get used to it. I myself had slight gagging reflexes on the first few days with the second tablespoon (about 15ml per tablespoon). Not because of the taste, because it is really tasteless and odorless, but more because of the substance of oil. From the second week, I no longer had this problem and this applies to many as shown by reactions on forums. The amounts that you can initially take without complaints vary per person. For example, I had trouble with a second tablespoon while on some sites it is even advised to start with a quarter teaspoon. MCTs can be used as cooking oil, but limited. They can only be heated to 150-160 degrees. At higher temperatures, oxidation and breakdown occur at the expense of taste.

When to Take MCTs?

That is a difficult question. I could not find any studies on this and the manufacturers themselves apparently do not know either. This is apparent, at least, from the totally different instructions for use on the packaging of various MCT brands. I myself ordered the MCT oil from Neobee at Bodyenfitshop, which states:

Recommended use: Take 2 servings of MCT oil as a dietary supplement daily. Take 1 serving in the morning and 1 serving 6-8 hours later.

However, the packaging of MCT oil from Best Body Nutrition states:

Take 1 tablespoon (15ml) before training and take 1 tablespoon before going to bed. Take a maximum of 3 servings per day.

Taking it before sleeping or after waking up, that makes quite a difference. Other producers do not even bother to specify the time of intake. If you consider that MCTs are fats that can be compared in certain respects to carbohydrates, then it seems logical to do the same with MCTs as with carbohydrates and fats. Taking them before going to bed becomes a lot less attractive (unless you gain weight very difficultly because it reduces your appetite at night when you sleep anyway and therefore do not eat less). In the morning, before and possibly after training seem to me personally the best times of intake.

MCTs: Better to Take with Carbohydrates

Above I already said that you can throw MCTs, for example, into a shake or salad. However, we have also read above that mixing LCTs and MCTs ensures that MCTs are relegated to the second rank in terms of metabolism and are processed differently. Mixing carbohydrates with MCTs, however, seems to strengthen the effect of MCTs (32, 33 Jeukendrup 95, van Zijl). By taking MCTs with carbohydrates, the MCTs are burned faster for up to two hours (see graph above) (33 Jeukendrup 95). In this study, 30 grams of MCTs (maximum that can be processed within 3 hours) were mixed with about 150 grams of carbohydrates. By mixing these, 71-76% of the ingested MCTs were burned instead of 33%.

…it was concluded that orally ingested carbohydrates accelerate exogenous MCT oxidation during the initial 2 h of submaximal exercise. – A.E. Jeukendrup, University of Limburg

Summary

• Many advantages are attributed to MCTs of which some have been demonstrated in studies and others appear controversial.
• MCTs differ from LCTs by having shorter carbon chains (6-10 instead of 10 or more carbon groups).
• MCTs follow a different path in digestion and metabolism than LCTs, thus providing energy more quickly.
• MCTs are naturally found mainly in coconuts and palm kernel oil, but are also synthesized in pure form.
• Most studies show that MCTs reduce body fat and total weight.
• Intake of MCTs causes satiation that lowers appetite in the hours after intake.
• The statement that MCTs spare muscle glycogen has been confirmed by only a few studies while most studies did not show this effect.
• Muscle breakdown was also not limited due to the stimulation of ketone body production by MCTs.
• Taking MCTs together with LCTs ensures that MCTs can no longer be used directly as fuel, but doubles the production of ketone bodies which can lead to additional fat burning.
• Amounts up to 80 grams of MCTs per day have been shown to be safe. In practice, the recommendations are between 30 and 60 grams. Possibly, the amount needs to be built up for acclimatization.
• Opinions differ regarding the times of intake. I recommend in the morning, before and after training.
• For better burning, MCTs are best taken together with carbohydrates.

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