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Supplementing With MCT Oil: Benefits vs. Side Effects

Article at a Glance
  • MCT oil is a type of fat the the body can use for energy.
  • One study found that MCT oil improved cognitive function in a group of “mild to moderate” Alzheimer’s patients who do not carry any copies of APOE4. This would suggest it is important to know APOE status prior to using MCT oil.
  • Common MCT oil side effects include massive increases in LDL-C, heart palpitations, and digestive discomfort.
  • Most of the evidence for MCT oil benefits in humans is weak, and more research is needed.
Genes Mentioned

MCT Oil supplements are popular in many circles, with health seekers using the supplement for everything from boosting cognitive function, to clearing the gut of unwanted pathogens, but what is the evidence for and against using this “healthy fat?”

Let’s dive in and evaluate both the benefits and side effects of supplementing with MCT oil. We will spare you the SEO filler, and cut right to the chase.

Evidence based benefits of MCT Oil

#1. MCT Oil can help achieve ketosis

MCT oil is a precursor to Beta-hydroxybutyrate, a “ketone” or fat molecule the body can use for energy. 1

There are two places you can get ketones from – you can eat them in supplement form or you can get them when your body burns its own fat stores. Supplemental ketones are known as “exogenous” ketones, and MCT oil is one of the best known exogenous ketone sources since your body can use it as a quick source of fat energy. 1

Keep in mind that not everyone is capable of achieving ketosis genetically.

#2. MCT as an Antimicrobial Agent

Some studies have shown the lauric acid found in coconut oil inhibited the growth of Clostridium bacteria, a major cause of antibiotic associated diarrhea.2

Others have found the medium chain fatty acids found in MCT oil were effective at killing multiple harmful pathogenic bacteria strains.3

Best MCT Oil for Killing Bacteria and Fungal Pathogens

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 the antimicrobial activity of 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).

Most of the research on the antimicrobial benefits of coconut oil have been focused on lauric acid and capric acid, rather than the ketone boosting caprylic acid.

#3. MCT Oil and Neurological Health

While many who have tried MCT oil notice a cognitive boost, what does the medical literature have to say? Are there studies which back up this effect?

I couldn’t find many (if you have some good ones please share in the comments). We do know that MCT’s can cross the blood brain barrier as fuel for the brain. There is this one 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.

Another, more interesting study, found that MCT oil improved cognitive function in a group of “mild to moderate” Alzheimer’s patients who do not carry any copies of APOE4.

For more on Alzheimer’s and diet, see this blog post.

Side effects of MCT Oil

In our view, most of the articles online listing MCT oil benefits have overreached in order to make their articles longer to please Google. The side effects and potential negative impact on cardiovascular health are, in our view, a larger part of the story with MCT supplementation, a regimen that involves massive doses of saturated fat.

#1. MCT Oil Can Raise “Bad Cholesterol”

There is a lot of bad information online about the impact of elevated LDL-C levels. While many in the low carb community like to question whether LDL is causal in heart disease in insulin sensitive people, the verdict is in – lower is better when it comes to APOB levels.

In many of us, a diet high in saturated fat will meaningfully increase LDL levels, which meaningfully increases the risk for heart disease over the long term. MCT oil carries with it mega-doses of saturated fat which will blow out LDL numbers in a subset of the population.

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As we learn from the Retterstøl study, the variability in response to a diet high in saturated fat is tremendous. Some will see little difference in their levels of “bad cholesterol” when using MCTs, others will see massive spikes. The people who see the big increases are known as “hyper responders,” meaning they see a large uptick in LDL-C when eating a lot of fat, especially saturated fat.

The bottom line is heavy use of MCT oil can increase levels of bad cholesterol in some people. That is a known side effect. From there, it’s up to you and your doctor to decide where you would like to see LDL levels stay for optimal health.

#2. MCT Oil and heart palpitations

Many people who take MCT oil experience heart palpitations. Studies in rats have shown saturated fatty acids and coconut oil to be proarrhythmic, meaning they stimulate heart palpitations.

#3. MCT Oil and Upset Stomach

This is a really common side effect of MCT oil, probably the most common. It’s well known that if you take too much, the “disaster pants” kick in resulting in diarrhea and unwanted trips to the bathroom.

Overcoming MCT Oil Side Effects

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.

Some find that they tolerate MCTs quite well at lower doses and when they use on a very occasional basis (twice a year). It is usually after multiple days of use that the worst side effects kick in.

How much saturated fat can your body handle?

Gene Food uses a proprietary algorithm to divide people into one of twenty diet types based on genetics. We score for fat metabolism, histamine clearance, carbohydrate tolerance, and more. Where do you fit?

Learn More

Key Takeaways

MCT oil offers an immediate source of fat energy that can bring with it noted benefits such as a boost in mood and cognitive performance.

However, supplementing with MCT oil is not without side effects. In some people it may cause calcium levels to rise in the blood leading to heart palpitations and a racing feeling.

In others, digestive distress will be an issue.

Last, if you see a major uptick in LDL after using MCT oils, take it seriously, not everyone can handle the mega-doses of saturated fat that come with MCTs.

Dr. Aaron Gardner, BSc, MRes, PhD

Dr. Aaron Gardner, BSc, MRes, PhD is a life-scientist with a strong background in genetics and medical research, and the developing fields of personalized medicine and nutrition. Read his full bio here.

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  1. Stephanie says:

    Omg !!!! I have been taking MCT oil with my morning coffee for a few months because i do intermittent fasting and a wellness physician recommended it. I had no idea it could be harmful ! I have been having extreme fatigue and palpitations for awhile now. Been to lots of drs had lots of tests and nothing showed up. This has made me depressed and anxious. My quality of life is suffering . I am nauseous again this morning and decided to look up can MCT oil cause nausea? And i found this forum and am gonna stop the MCT oil now and see if my heart palpitations go away. I am hopeful that this is the cause. Anybody else have severe fatigue and / or arms tingling and weak ?

    • Terry martz says:

      I have had upper stomach pain and bouts of severe diarrhea and with doing some research I’ve decided not take the MCT oil any longer. Thank so much. No palpitations

  2. Mcohen says:

    I have been on keto for 3 wks and taking mct oil- a tablespoon in the morning, and a tsp at lunch- this weekend the acne hit! All over both cheeks! I am not happy! Knew it had to be something new that i was eating so thru process of elimination arrived at mct oil. Started researching so happy to have found this forum! I agree with person who said that this supplement needs closer scrutiny before being sold as harmless! I have also had buzzing in my head! Time to drop the mct oil! Thank you everybody!

  3. 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.

  4. 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!


  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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?

  11. 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 !

  12. 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.

  13. 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.

  14. Rafael says:

    Processed MCT oil is toxic. It causes severe gastrointestinal distress. Use pure natural coconut oil instead.

    • 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.

  15. 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

  16. 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

  17. 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.

  18. 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,

  19. 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.


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