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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 lauric and capric acid provide better support for maintaining gut health.
Genes Mentioned
MCT oil side effects

Hey, thanks for stopping by. 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 can help reduce harmful bacteria in the gut.

I currently take MCT oil in low doses a few times a month to maintain gut health, but also for energy. 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.

MCT oil benefits

The MCT oil I used 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 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) For more on preventing antibiotic associated diarrhea, see: S. Boulardii: the antibiotic resistant probiotic.

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.

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 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

Forum accounts of MCT 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.

I now find that I tolerate MCTs quite well at lower doses.

Choosing a good MCT Oil

So, you’ve read the potential side effects and still want to give MCT oil a shot?

There is a ton of marketing surrounding MCT oil. Now that I have decided to supplement with the product on occasion, I have added MCT oil reviews of some of the top brands on Amazon. Consumers may be worried what they’re getting in the manufacturing process, so we’ll mention if hexane — an organic chemical compound used as a solvent — is present in each (it’s not in any of the brands we reviewed). You generally want to steer clear of MCT products made with hexane.

MCT oil brand comparison

BrandIngredientsHexane extracted?
Viva Naturals Non-GMO Pure Coconut MCT Oil60% caprylic acid (C8) and 39.7% capric acid (C10)N
Sports Research Premium MCT Oil38% C8, 31% C10, 31% lauric acid (C12)N
Brain Octane Oil100% C8N
Left Coast Performance MCT Oill56% C8, 44% C10N
NOW MCT OilAt least 60% C8, 35-40% C10, 0-5% otherN

Viva Naturals Non-GMO Pure Coconut MCT Oil – Good product

Viva Naturals MCT Oil, made from 100% sustainably harvested coconut, is non-GMO and paleo/vegan-friendly. Viva Naturals is not mixed with any other MCT sources and is flavorless and odorless. The company previously used palm oil before this product version.

Ingredient breakdown: 100% pure, plant-based capric and caprylic acid that have been naturally extracted from the pulp of fresh coconuts. To isolate MCTs from other fatty acids, the oil is fractionated and purified without the use of solvents or harsh chemicals and tested via a third-party lab. Fatty acid percentages: 60% caprylic acid (C8) and 39.7% capric acid (C10).

What reviewers are saying: Increased energy with minimal side effects. Lots of props for being tasteless, and has helped some reviewers lose weight quickly.

Sports Research Premium MCT Oil – Recommended as antimicrobial

The Sports Research brand of premium MCT oil is 100% coconut sourced with no palm oil, containing the full spectrum of MCTs. This MCT oil is registered with the Vegan Society and is non-GMO verified, certified paleo. Sports Research stresses the benefits of lauric acid, in particular, for gut health. This isn’t the product to use for the energy seeker, but for those looking for a product to manage pathogens like Candida, this product is a good choice as it contains both capric and lauric acid. 

Ingredient breakdown: Derived from organic virgin coconut oil. Does not contain long-chain fatty acids. Fatty acid percentages: 38% C8, 31% C10, 31% lauric acid (C12).

What reviewers are saying: Increased energy, but reviewers recommend low doses to start to minimize side effects. One user with an autoimmune disease highly praised the product alone as giving a higher boost of energy over their previous fatty coffee ingredients (organic coconut oil, grass-fed butter, grass-fed heavy whipping cream).

Brain Octane Oil – Recommended for ketone production, energy and mental clarity

One of Bulletproof’s popular offerings (the other is XCT Oil), Brain Octane Oil is distilled from 100% pure coconut oil. It differs from other products in that it supports cognitive function completely through caprylic acid and no other MCTs. It’s also one of the pricier brands out there.

Ingredient breakdown: Unlike its XCT Oil, which is a combination of C8 and C10, Brain Octane is only comprised of caprylic acid, which is said to convert to ketones faster. Fatty acid percentages: 100% C8.

What reviewers are saying: Brain fog diminishes, and has even helped a couple of dementia patients with increased focus and improved mood. Some reviewers note softer skin and a better complexion, as well. Many report higher boosts of energy than with blended C8/C10 products, and Brain Octane Oil side effects of the gut variety appear to be light.

Left Coast Performance MCT Oil  – Neutral

Left Coast Performance MCT oil is triple-filtered and manufactured at a Good Manufacturing Practice facility in Iowa. Each batch is created using a low-heat, time-consuming process. Fun fact: The company recently upgraded to coconut-only MCT oil and does direct-to-consumer sales only, offering a full refund for customers who experience upset stomach.

Ingredient breakdown: Made from 100% fractionated coconut oil; vegan, gluten-free, and paleo-friendly. The company tests every batch for heavy metals and impurities. Fatty acid percentages: 56% C8, 44% C10.

What reviewers are saying: Suppresses appetite and no upset stomach when using the recommended dosages (less than ½ tsp in a coffee or smoothie if new to MCT oil; 1-2 tbsp one to three times per day for those accustomed).

NOW MCT Oil – Neutral

NOW MCT Oil is marketed as a vegetarian product, and 100% pure MCT oil. What you get in C8 could be a mixed bag based on the ingredients, however, but it’s mostly a C8/C10 blend. All raw materials are tested for purity.

Ingredient breakdown: This product is a combination of coconut oil and palm oil. Fatty acid percentages: at least 60% C8, 35-40% C10, 0-5% other.

What reviewers are saying: Enjoyed mixed in with salads as well as smoothies or coffee. Comes in a glass bottle, which some reviewers found to be better than most brands’ plastic. Did reportedly raise one reviewer’s triglycerides.

Choosing the winners

We haven’t reviewed any “bad” MCT products in this post — we’ve included only quality formulas. If you’re having a hard time choosing, the bottom line is that different brands of MCT can be used for different purposes.

Sports Research MCT Oil comprises about 33% lauric acid, and reduced caprylic acid, so it’s not the go-to MCT oil for energy, but it may have added antimicrobial benefits for maintaining gut health. Most of the research on the antimicrobial benefits of coconut oil have been focused on lauric acid.

However, if energy and focus are your goals, caprylic acid should be the focus. Most good-quality MCTs filter out the lauric acid (which we don’t necessarily love) as part of the manufacturing process, so we’re left with just the ketone-boosting caprylic acid. Choosing between high-quality products really comes down to how well you tolerate caprylic acid.

If you tolerate MCTs well, Brain Octane is the winner.

If you’re like me, and want a slightly less potent MCT with lower levels of caprylic acid, try Viva Naturals.

John O'Connor

John O'Connor is the founder of Gene Food and an Integrative Health Coach, trained at Duke IM. He lives in Austin, Texas.

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  1. 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?

  2. 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.

  3. 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

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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!

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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 …

  15. 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?

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  21. 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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