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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. Pam james says:

    Help! I started the keto diet 10 days ago. For the last five days very tired. From reading probably the so called keto flu. Read the MCT Oil will give one more energy. Then, I read one of the side affects of the Mct oil was fatigue!! What is it fatigue or energy? How does one product do both?? Has anyone had this keto flu stuff also??I am floating away with water and pinches of salt which has helped but still feeling tired. I am also surprised because I had taken a lot of carbs out of my diet for a year before I even went on the keto diet. Just trying to loose ten pounds that is it. Weighed the same amount for 30 years until my thyroid went bipolar and gained ten pounds in 6 weeks

    • Kelly in California says:

      Pam, a good way to support your thyroid is to supplement your iodine intake. There is iodized salt if you add salt to your diet (as stated in your comment). I personally take a iodine supplement (liquid) and it has evened out my body temperature as well as slowed my hair loss from alopecia (I have every autoimmune disease that Rheumatology has to off – 30+ diseases – except I don’t have RA aka Rheumatoid Arthritis. I am unable to gain weight and can now fluctuate 2 to 4 pounds throughout a month which is a big deal for my situation. I give credit to the Iodine supplement. If you would like more information about the specific one I take, please let me know and I will be happy to share that information with you. Best of luck to you with your health goals. Kind Regards <3<3<3<3

  2. Denmark says:

    I just realized that different MCT are used for different purposes. Now, I can choose what is exactly the right MCT for my goal. Thanks for making me realize about it!

  3. Leticia says:

    Hi john! Do you have any info regarding MCT pills? I’m not a big fan of the liquid version. I saw a pill version from the brand KETO, and it seemed pretty reliable by the reviews

  4. Sara says:

    Do you know if Perfect Keto Collagen or MCT powder contains hexane in it? Do you recommend this brand? I’m currently taking both.

  5. E says:

    Do you think MCT oil causes stomach upset and/or bathroom issues with FIRST use, or just after several days regular use? I want to try adding a very small amount to smoothies (maybe 1/4 TBSP) but nervous about this.

    Did you take your oil with coffee? I personally have issues with overheating/sweating when drinking coffee (and caffeine is known to cause that in some) plus a mild allergy to it (that didn’t show up til after 30).
    Maybe your overheating was cause of coffee??

    • Name says:

      “Bathroom issues” – can be the very first day of taking because it is oil. If you haven’t already, try a small dose (eg one tsp) and increase to see how you do.

  6. Susan Matthews says:

    You stated that MCT oil goes not to the lymphatic system but straight to the liver. That is incorrect coconut oil Maybe but MCT oil does not go straight to the liver it bypasses the liver into the lymphatic system.
    don’t misconstrue something so important, people with liver disease like me benefit from MCT oil because it bypasses the liver. The liver doesn’t have to work as hard I think you need to get a little educated. I’m seeing other comments on here were you have made allegations that aren’t true….
    Maybe you should brush up on it a little not just tap into the first website you see. Maybe look up MCT oil with dr. Eric Berg or MCT oil with Thomas delauer on YouTube.

  7. victoria says:

    Keto is NOT Atkins ( i can understand the reference though) . Also the proteins in the Atkins diet would hinder your body’s ketones synthesis . Another thing is that the ‘fuel preference’ for the body is only carbs IF you are not on the ketogenic diet at which time the preference is fat ( which breaks down into ketones ).
    I’m using the Jarrow (C8 & C10) but I suggest easing into it . I started at 1/2 a teaspoon graduating the same amount every day until I got to one tablespoon . This works for me very well .
    I also use coconut oil quite a bit in my cooking as well as take caprylic acid from time to time.
    Maybe the presence of medium chain fatty acids in my diet deferred the side effects ?
    Hope this helps …

  8. Amanda Hjortshoej says:


  9. David ONeil says:

    I’ve never used mct oil. So I’m unsure of my reaction to it. Which mct oil is the best for first time use?

  10. Scott says:

    I’m curious as I have often done the Atkins Diet. I thought the the whole idea was to cut out carbs so that your body rids itself of this fuel source, therefore bringing on Ketosis, which is a state of the body burning it’s own fat for fuel. This is how one loses Fat and Weight. By introducing this MCT into the mix, isn’t it like introducing an alternate fuel source therefore reducing the benefit of using one’s own fat for fuel ?

    Just very curious about this. Thanks for any help.

    • Joe says:

      No, mct is a fat not a carb, it’s just a quickly processed carb, ie the metabolic pathway isn’t as long, so it acts like carbs in that way, not as glucose.

  11. Neil Levin says:

    I am the Senior Nutrition Education Manager for NOW. Our MCT Oil is NOT processed with hexane. We don’t know why you mistakenly claim this, but it is a false allegation. Just today, I have personally reviewed the documentation and flow charts from the producers that we use and no hexane is used or needed to produce MCT oil from coconut and/or palm oils. I can’t imagine how you came to claim something that isn’t true, but please correct your article and the rating of our product to avoid false product disparagement. Our MCT oil is about 60% C8 and typically 99.7% C8 + C10 combined. The other 0.3% is typically split between C6 and C12.

    • Andrew says:

      Thanks for the clarification. I saw that Now Sports MCT Oil made the above list partly because it didn’t contain Hexane. And then became confused when I noticed that a commenter mentioned Hexane being in the formula and the article author, John O’ Connor, hadn’t refuted the claim. I just purchased Now Sports MCT Oil. Again, thanks.

  12. Carol says:

    I drink Nature’s Way MCT oil from coconut oil. I haven’t had side effects until I spilled too much in my shake and didn’t want to waste it so I drank it. I’m nauseous and looking for something to counter this effect. I’ll definitely stay away from it for a while – but I’d like to feel better sooner.

  13. Gingin says:

    I bought Now Sport MCT oil and didn’t know it had Hexane
    Since I bought it at my Coop Health Food Store
    I’ve been using it for about a month
    Do u think I may have damaged my liver because of the hexane ?


    I have been using Viva Naturals for the past month. Start at 1/2 teaspoon, now I’m up to one tablespoon a day. I have lost 17 pounds in 30 days. My digestion seems much better. I get a burst of energy after 30 minutes. I have no complaints what so ever. Bought on Amazon, lighting deal for $18.00 for 32 ounces.

    • Claire says:

      Please how are you doing with the Viva Naturals MCT oil. It is now August 2018 almost a year since your review.
      I am just now researching to find one MCT oil to use for the first time. I would greatly appreciate your response and direction.

      Thank you.


    • Kimberley, I can’t say because I’m not familiar with the brand, but at that price point I’d probably buy XCT oil from Dave Asprey (Bulletproof), especially if you were looking for a product that is exclusively caprylic acid.

  15. Neal says:

    Greetings John.
    I have gotten good results from Nature’s Way MCT oil. It’s made from 100% coconut oil produced in Singapore.


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