Last updated on

My Experience With MCT Oil: Benefits vs. Side Effects

Article at a Glance
  • MCT oil is often taken as an energy-boosting supplement that raises ketone levels, the source of energy the body uses when it burns fat instead of glucose.
  • MCT oil is high in saturated fat. When combined with high doses of Vitamin D, use of MCT oil may increase the levels of calcium in the blood, especially in certain VDR genotypes.
  • MCT oil has anti-fungal and antimicrobial properties that may cause a die-off reaction in those with compromised immune systems.
  • Some common MCT oil side effects include fatigue, light-headedness, energy drops, increased heart rate, and diarrhea.
  • MCT oil with high caprylic acid content is best for energy, while products that keep a higher ratio of lauric and capric acid provide better support for maintaining gut health.
  • We like Brain Octane Oil for energy based on high levels of caprylic acid and Sports Research MCT for gut balance since it maintains about 31% lauric acid.
Genes Mentioned

Scientifically reviewed by Dr. Aaron Gardner

MCT oil side effects

I originally wrote this post to highlight side effects of MCT oil that weren’t frequently discussed in other forums. Reading this post will give you all of that information, as well as the reasons some people may benefit from taking MCT oil, even if smaller doses is all they can handle.

Without removing the piece I wrote on side effects, I have added “update” sections throughout this post to give my current thinking on MCT oil, which is more positive in light of some research I’ve come across highlighting not only MCT oil’s energy production benefits, but also its potential as a natural antimicrobial and anti-fungal supplement that may help reduce harmful bacteria in the gut.

I currently take MCT oil in the form of Dave Asprey’s “Brain Octane” oil in low doses a few times a month for an energy boost. Taking it more often seems to increase my lipids to levels I don’t like, so this is a very occasional supplement for me.

In light of my VDR genotype, I try not to take vitamin D supplements alongside MCT oil. Aaron and I came up with a genetic hypothesis linking variants in the VDR genes to MCT oil sensitivity. Those of us with VDR “mutations” may want to avoid the combination of high IU doses of vitamin D with MCT oil, as the combo may increase serum calcium levels to uncomfortable levels. This is a theory we’re advancing based on our research, it is not yet proven. We lay out the details of that theory in this post titled VDR Fok1, Vitamin D, Fat and Heart Palpitations.

As MCTs are a product I now use on occasion, I had my staff do a review of some of Amazon’s top selling brands and come up with the best based on manufacturing process and ingredients.

OK, now on to the original post.

Ketones motivated my first MCT oil experiment

After listening to a number of podcasts devoted to the benefits of nutritional ketosis, and ketone bodies in general, and after reading resources like Dr. Peter Attia’s Eating Academy, I decided to experiment with MCT oil in the mornings. My normal dose was between 1/2 and a full tablespoon, which I usually added to a smoothie. For those of you who aren’t yet familiar, MCT oil stands for “medium chain triglycerides.” Advocates of ketogenic diets (basically a fancy new name for the Atkins diet) love MCT oil because it is a source of non-glucose derived energy for the body, and it ups your blood ketone levels.

This article gives some nice background:

Many ketogenic diet and MCT oil spokespeople say that MCT’s energy sustaining powers can be explained as follows: when MCT oil is metabolized in the body, it behaves more like a carbohydrate than a fat. Remember that the fuel of preference for the body is carbohydrate. Unlike other fats, MCT oil does not go through the lymphatic system. Instead, it is transported directly to the liver where it is metabolized so it releases energy like a carbohydrate and creates lots of ketones (which can be used for fuel) in the process.

What are the benefits of MCT oil?

The MCT oil I used originally was comprised of 55% caprylic acid, 36% capric acid, and only 0.2% lauric acid. Initially, I saw the power of MCT oil and loved the benefits.

Small doses, of even 1-2 teaspoons, gave me a significant increase in brain function, and a burst of energy. I normally function at a fairly high level cognitively, but the MCTs gave me an “edge” that allowed me to maintain focus for longer periods of time.

My brain felt razor sharp.

See also: The blood type diet has been debunked, or has it?

MCT as an antimicrobial agent

Update: As I mentioned above, I am now taking MCT oil again, this time at a lower dose than before. I now find that cycling MCT oil usage gives me the greatest benefit as using small amounts everyday causes my body to adapt to the MCT, and I don’t get the same “pop” I get from irregular use. MCT oil’s antimicrobial benefits motivated my decision to use the supplement again.

This study demonstrates that the lauric acid found in coconut oil inhibited the growth of Clostridium bacteria, a major cause of antibiotic associated diarrhea. (R)

This study also caught my attention. The findings here were that the medium chain fatty acids found in MCT oil were effective at killing multiple harmful pathogenic bacteria strains. (R)

Then, there is this study which shows that lauric acid and coconut oil reduced ammonia levels in cows. This study is of potential interest for those with genetic variants that have the potential to increase serum ammonia levels, namely urea cycle SNPs as well as CBS gene mutations. It is important to keep in mind that most MCT oil has the lauric acid removed, since lauric acid doesn’t function as an immediate energy source like caprlyic or capric acid does. If your goal is lauric acid, it’s better to just take a spoonful of coconut oil rather than resorting to MCTs.

Capric acid is a known anti-fungal agent, and has shown the ability to kill Candida in vitro (in test tubes). (R) In light of the antimicrobial and anti-fungal capabilities of capric and lauric acid, one of the causes of MCT oil side effects for some people could be an overload of toxins known as a “die off reaction.” Essentially, those with immune systems compromised by pathogens get flu like symptoms when the bad guys die off faster than their bodies can process the toxins.

MCT oil and the brain

While I, and many others, experience a noticeable cognitive boost from supplementing with MCTs, what about the medical literature? Are there studies which back up this effect?

I couldn’t find many (if you have some good ones please share in the comments).

There is this study which looked at the ability of MCT oil to increase ketones levels in the brain of Alzheimer’s patients as a way to make up for impaired glucose metabolism. The study found that MCT use doubled consumption of ketones in the brains of Alzheimer’s patients.

MCT oil side effects

Initially, over the course of a week’s worth of usage, with dosage never exceeding 1.5 tablespoons per day, I started to develop some side effects that temporarily made me stop using MCT oil.

I am a fan of Bulletproof Radio, Dave Asprey’s podcast, and have heard him extol the virtues of MCT products like the one he adds to Bulletproof coffee. Most of us have felt the surge of energy that comes from a morning of fasting, or just a light breakfast with protein. I figured a small dose of MCT oil would enhance this state, but over the course of a few days, I experienced episodes of fatigue, energy crashes, light headedness, increased heart rate, and on two occasions, minor heart palpitations. After first starting the regimen, I also experienced a mild version of what Dave Asprey likes to call “disaster pants,” which is a common MCT side effect.

You get the idea there.

More sensitive to heat

Bottom line is it felt to me like the MCT oil increased by body temperature as it built up in my system over time, making me more sensitive to heat, and causing my heart to beat hard when it normally wouldn’t (again likely caused by high >5,000 IU doses of Vitamin D). For a few days after stopping with MCT oil, I still felt light headed and noticed increased heart rate and overheating. It took a few days to get back to normal.

Update Note 4/30/18: I now believe this was caused by a combination of my VDR genes combined with high dose Vitamin D supplements that I took alongside the MCT oil. I have cut back some on vitamin D, although I still take it, but I seem to tolerate MCT oil much better when I cut down on my vitamin D IU dose, and when I take a smaller dose of MCT oil.

See also: MCT oil brand comparison

Potential lipid problems with MCTs

It’s wise to measure metrics like LDL-C, Lp(a), and LDL-P before and after taking MCT or before doing a Bulletproof style Paleo diet. Some won’t see any changes, but certain individuals will see a spike in LDL-P as the saturated fats in MCT retard LDL particle clearance through the liver.

For more see:

Why is my LDL-C so high on a Bulletproof Diet?

Is the Paleo community right about saturated fat?

Forum accounts of MCT oil side effects

When you start digging around online, you come across a number of forum discussions with people reporting some of the issues with MCT use that I experienced. I’ve included links below.

Man reporting MCT oil caused heart palpitations

Man reporting heart racing after upping coconut oil intake and after supplementing with MCT oil

Man reporting heart palpitations after drinking Bullet Proof coffee and going on high fat diet 

Everyone’s body is different

It could be that some people do best staggering use of MCTs to once or twice a week to get benefits on those days, but avoid regular use so as not to trigger the side effects that come as making MCTs part of your daily routine. As with anything else, proper dosing is key.

It’s also important to have an idea of how your body will react to saturated fat from a lipid standpoint. New studies are teaching us that based on variability in LDL receptor activity due to mutations in genes like PCSK9, people respond very differently to high fat diets. Through our custom nutrition plans, we try to give clients an idea of what their likely genetic ability to clear LDL particle is. Lower clearance cautions in favor of a diet that is lower in the intense doses of saturated fats found in MCTs.

I now find that I tolerate MCTs quite well at lower doses and when I use on an occasional basis.

John O'Connor

John O'Connor is the founder of Gene Food. He is passionate about nutrition, genetics, and wellness and uses this blog to publish self experiments as well as some of the research that the Gene Food team does internally to highlight stories of bio-individuality.

The very latest on genetics, nutrition and supplements delivered to your inbox!


Leave Comment

  1. Dina Barzilai says:

    shocked at all the negative effects people experienced. Wondering if some is just toxins exiting their body…I had diarrhea for the first 2-3 days i started, a couple of zits which aren’t typical for me but can’t say for sure was the oil…then nothing. Did not even notice any benefits, either, altho i only took it a week or so before running out…my boss gave me about 1/2 bottle of Asprey’s Brain Octane…haven’t ordered more but planned to…trying to improve brain function and lose weight.

  2. Sangeeta Kauchhur says:

    I’ve been using 2 tsps of MCT oil daily with my coffee and noticed weight gain despite being on keto diet!! I’m 55 years old.

    Has anybody had similar experiences? All reviews advocate MCT oil for weight loss so Im extremely confused!


  3. Tonja Bartlett says:

    I nearly died from MCT oil. I didn’t even eat it, just put a little bit on my face. Woke up with my heart going so fast I needed to go to the ER….if you have any kind of health issue, especially heart problems, I would NOT recommend it. I have an irregular heartbeat and it sent my heart rate through the roof. Also turned my skin yellow so obviously affects the liver as well. NOT a very safe product in my opinion. I am certified in fitness and nutrition and believe me I would never tell anyone to use this stuff.

  4. Laurie says:

    Has anyone had pain in their feet? I’ve been experiencing pain that seems to be in the bones of my feet. I took MCT oil for several months (October – December) and then stopped because I finished the bottle. At that time my feet were hurting making walking painful, but the pain seemed to disappear on its own after a couple of weeks.
    Approximately two months later I purchased another bottle, and since I have been using it (March – June) the pain has returned. Maybe it’s a coincidence, but I’m wondering if anyone has had a similar experiences.

    • jodi says:

      Started using mct oil about two weeks ago now , and my legs are swelling and yes my feet hurt, I am thinking my feet hurt from my legs being swollen. Not sure if mct oil is causing this? I also have a thyroid issue and I am researching if it is ok with that condition?

  5. Ashlee says:

    I have been using MCT oil and have ended up with Keto Rash and also really bad acne on my face. I don’t have a gallbladder and had gastric bypass back in 2015. I don’t understand why the MCT oil would cause me to have acne.

    • Domica Nelson-Polk says:

      I’ve been taking it for the last couple of weeks & now I too have acne! WTF?! And it’s bad acne! I’m not going to continue taking it. Thanks for ur comment bc I never would hv known it was the oil for I’ve added a couple different natural supplements that I was taking along w the oil.

    • MiMi says:

      I’ve been taking it for the last couple of weeks & now I too have acne! WTF?! And it’s bad acne! I’m not going to continue taking it. Thanks for ur comment bc I never would hv known it was the oil for I’ve added a couple different natural supplements that I was taking along w the oil.

  6. Travis says:

    I recently took a small dose of the MCT oil from the bulletproof brand on a Monday, then again on Tuesday. Two days later I got the worst headache of my life, I don’t get migraines or headaches at all. The pain was a 9/10! I can’t say for sure yet that it was the MCT oil. I’m still working with Doctors to figure out what this is. My head pain is gone finally after 6 days and now my head just doesn’t seem the same. I feel light headed and just out of it. For now I’m going to stay away from the MCT oil. I’m trying to do research on the oil to see if someone else has had these same symptoms.

    • Chris says:

      Exactly the same experience, 9/10 unprecedented headache for days. Added maybe a half-Tbsp of MCT Oil to coffee, a day or two passed, then brutal headache for a day. Didn’t connect the two, so a week or so after that, added a Tbsp (maybe more) of MCT Oil to my coffee. Two days later was utterly laid out with unilateral, constant headache. I’ve never been had headaches, and I surely have never experienced headache like this. It has been going on for four days and nights now, and is just starting to diminish. I was scared to take ibuprofen, I thought I might have a brain bleed! I can’t even bend down at the waist–the added blood pressure is excruciating. This is the fourth day I’ve spent lying down with my head elevated. There’s no headache ‘onset,’ it’s just ongoing. It’s not made worse by light. There’s been some nausea, fever, and chills as well. It can’t be flu, because this bizarre headache is far above and beyond anything one would get with flu, or any illness or infection I’ve had. MCT Oil can’t be on shelves until this is explained and people at risk can be warned. No one would be able to work, drive, or take care of their children with this kind of pain.

  7. Helen Bush says:

    I also have had my gallbladder removed. When I take the MCT oil to break my fast or sometimes after I also experience cramping, gas and sometimes moderate nausea followed by large amount of loose stool. This is with only 2 teaspoons of MCT. Any advice anyone can provide would be appreciated.

    • PeaJay says:

      Your symptoms are normal for someone having their gallbladder removed when consuming a concentrated oral dose of fatty oil. I haven’t had a gallbladder for over ten years. If I eat a meal of deep fat fried foods, or oily salad dressing, or ice cream, etc. I get the same symptoms.

  8. Shannon T. says:

    I had my Gallbladder removed 6 years ago, I have been doing keto diet an taking MCT oil.
    I get so sick, cramping ,light headiness, where I want to pass out and run to the bathroom. If the oil goes right thru me I am getting any benefits from the MCT OIL? Is there something else I could take instead of MCT oil?

  9. Kate says:

    I tried MCT oil and loved the mental clarity in sports. However, by afternoon I would hit a hard crash of needing to sleep. Read somewhere adrenals could be affected, so stopped the oil.

    I now have started with some brain boosting supplements and am seeing good results in my focus in the sports. However, again I’m hitting the hard crash in the afternoon. I thought I’d take a 20 minute nap and woke up over 1.5 hours later. More of an exhaustion.
    I’m searching to try and find out why.
    I think I will do as is suggested to not use every day. Which I haven’t been, but at 3 times a week it seems to take me down physically later in the day.

    Wondered if anyone else has had this problem? I loved the stuff!!! I used the Bulletproof Brain Octane.

    • Brenda Dominguez says:

      Yes I eat mostly same foods everyday , I started taking xct oil in the morning, at first the first few days I felt awesome thought wow I have mental clarity a lot of energy for the whole day I started with tsp . The second week I just felt extremely fatigue lightheaded and my heart beat was abnormal. I knew the only new thing I added was the xct oil . I was taking 1 tablespoons of coconut oil never had any problem but I had heard xct oil and Mac oil were great sources of energy and it is at first until few days later there are side effects !

  10. Yonah says:

    Almost a year ago I had an anaphylactic reaction to a shake I made with MCT oil. I thought it was another ingredient, not the oil. I laid off the shakes and oil until about a week ago. All good for about 3 shakes until today, when I had another allergic reaction. This time I was aware of what was happening and took Benadryl before it got out of control.
    Anybody? Anaphylactic reaction to MCT oil?

    • Vera says:

      Hi Yonah, I too had a reaction to MCT oil that sent me to the hospital. Be careful!
      It also dorpped my blood pressure to the point that I was loosing consciousness and was unable to link MCT oil to the problème until after four months of hell, I stopped the oil and am now recovering.

  11. Laurel says:

    Just wanted to put this in the mix. I have taken 3 scoops a day for 2 month and experienced heart palpitations that I think are a result of MCT oils. Also taking exogenous ketones very minor amount. Anywho, I just had a severe tachycardia episode with heart rate over 200 and couldn’t get it to stop and never had before. None of the things they think could trigger something like this I don’t do, like smoke, drink, caffeine, etc. ON top of that I’ve felt horrible for a good 3 weeks. I mean they did discover a UTI in the emergency room but that’s all. I cannot find anything on the Inet about daily dosages and just wanted to throw this out there in case any one else experiences this. I have to make a cardiologists appointment but I bet he doesn’t find a thing that caused it but will update so as not to throw MCTs under the bus if it’s not necessary. BTW haven’t taken MCT for 3 days and no heart palps since.

    • Dan says:

      It’s not toxic, it’s simply more concentrated as MCT oil since natural coconut is basically ~50% (approximately) MCT. The idea is to use less, since MCT oil essentially a concentrate.

    • Ned Meyers says:

      “Processed MCT oil is toxic.” Yeah. No it’s not. I visited two U.S.-based MCT oil producing facilities to research my dissertation on human dietary fat adaptation. The MCT oils are naturally extracted from coconut oil through a process of steam and semi-permeable membranes. If “processed” MCT oil is toxic then so is coconut oil.

  12. Usman says:

    I don’t know anything about MCT oil and Iam just thinking about using it for weight loss which product you think is best for me To start. Thanks

  13. Cherie says:

    I started taking 2 Tbls a day with breakfst and dinner about two weeks ago. I have Celiac’s and I can see that it is helping recover after being “glutened” after eating out. It is definitely helping gut health, fat loss, and absolutely has made an improvement in speeding up memory and thinking quickly and clearly again. .I exercise consistently I am seeing a shift in my metabolism of FAT enough that people are starting to notice the change even the scale is just barely creeping down. But, the last two days I’ve experienced what I think is a side effect of getting hot and my head POURing sweat. I’m 60 and haven’t had hot flashes in years and this isn’t typical of those either. This is just my head that sweats. I’ll experiment with a lower dose.

    • Maria says:

      Hello I will be turning 60 and I wanted to know what MCT oil you use, that was helpful in your fat burning and clearer thinking?
      John O’Connor did mention in his article above that if you take Vit D with MCT oil then that could cause the symptoms you are experiencing. He said to take lower doses of the MCT oil and not with D vitamin.
      Thank you

  14. Virginia says:

    Is Purely Inspired 100% pure MCT Oil a good brand. I have Hashimoto’s and n matter how I cut back on carbs, drink a lot of water and do moderate exercise, I keep gaining weight. I thought the MCI Oil would speed up my metabolism.

  15. Diane Bailey says:

    I’m curious to know if MCT oil can cause detox that manifests as long bone pain. Specifically femur shank. I once experienced severe extremity pain…bone pain…when a D.N. suggested a detox regime that was too aggressive. Just curious. Not severe enough that I”m going to abandon use.

    • Arlie Staab says:

      I’ve been taking two tbsp of MCT oil a day and on the sixth day I woke up with severe pain in long bones of both legs. I couldn’t imagine what was going on. I’m a retired RN and was checking off what all it might be. Also had a headache. Finally decided I was coming down with a flu bug and took an extra strength pain pill and went to bed all day. The next day woke up, same problem. Decided to do some on line research about MCT oil and found this site,

  16. John T. says:

    Began using NOW MCT about Dec 6, 2018. I don’t particularly measure amounts that I use I just pour some on top of cider three times a day. Noticed that seemingly incurable to fungus is starting to disappear. I’m 79 years old and began taking MCT mostly for short term memory improvement, it helps. Side effects for me, reduced belly fat, better short term memory,
    anti bacterial and fungus obvious. Good stuff for aging body I am sure.

Leave a Reply

Facebook icon Twitter icon Instagram icon Pinterest icon Google+ icon YouTube icon LinkedIn icon Contact icon Info icon