What do I do if I get diarrhea on a ketogenic diet?

By Dr. Stephen Phinney and the Virta Team

There are three common errors made with a poorly-formulated low carbohydrate diet that can cause stomach and intestinal upset and diarrhea: sugar alcohols, too much protein, and the wrong source of dietary fats.

Diarrhea is not a common side effect of a well-formulated ketogenic diet. If it occurs, it likely due to well-intentioned but incorrect food choices. But while sorting this out, it is important that you stay hydrated and replenish your electrolytes!

It is also important to note that there are many causes of diarrhea independent of a ketogenic diet, so contact your doctor if your diarrhea causes severe symptoms or lasts longer than a week.

You may need to take a closer look at what you are eating.

Ask yourself a few questions:

1. Are you a frequent consumer of sugar free beverages, candies, protein/diet bars, and sugar substitutes? These can cause diarrhea.

Sugar free and low carb products frequently contain sugar alcohols to give them a sweet taste while avoiding table sugar (sucrose). These sugar alcohols (xylitol, sorbitol, mannitol, maltitol, lactitol, and isomalt) have been known to cause gastrointestinal distress (Makinen, 2016). Of these, sorbitol is the least tolerated, but all of them can cause gas, nausea, and diarrhea if consumed above one’s level of tolerance. Thus, eating fewer products containing sugar alcohols may help with your diarrhea.

This video explains the connection between sugar alcohols and gastrointestinal distress:

2. Are you eating low carb, low fat, and high protein? Too much protein can lead to diarrhea.

Remember, a well-formulated ketogenic diet is low carb, high fat, and moderate protein. When cutting carbs, it can be tempting to increase your protein without increasing your fat, but the resulting high protein diet can lead to diarrhea (Speth, 1983). It is important to keep protein at about 10-20% of your daily energy need and add ‘good fat’ for satiety. More on what constitutes ‘good fats’ below. Read more on how much protein you need on a ketogenic diet

3. Are you choosing the right sources of dietary fat? Some oils can cause diarrhea.

While a little bit of omega-6 and omega-3 essential fats are required from our diet, more is not better. In particular, our digestive systems have a limited tolerance for vegetable and seed oils high in omega-6 fats. Early in our human research, we found out that feeding our patients a high fat diet made with soybean, corn, safflower, or sunflower oils promptly made them feel nauseated and caused diarrhea. Given that a well-formulated ketogenic diet eaten to maintain body weight provides 70-80% of one’s daily energy intake as fat, the majority of this fat intake needs to come from mono-unsaturated and saturated sources such as olive oil, high oliec versions of safflower and sunflower, coconut oil, lard, butter, cream, and high fat cheese.

Here are some fats and oils that we recommend:

Keto diet - acceptable fats and oils

Citations:

Makinen KK. Gastrointestinal Disturbances Associated with the Consumption of Sugar Alcohols with Special Consideration of Xylitol: Scientific Review and Instructions for Dentists and Other Health-Care Professionals. Int J Dent. 2016; 2016: 5967907.

Speth JD, Spielmann KA. Energy source, protein metabolism, and hunter-gatherer subsistence strategies. J Anthropol Archaeol 1983; 2:1–31.

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20 Comments

  1. I had some GI issues when I first started on the keto diet. It took a bit of trial and error, but I found that removing sugar alcohols cleared it up right away! Now I use stevia…worse taste but totally worth it!

    Reply

  2. My issue was too much MCT oil. Once I cut back on that, and gave up diet soda, my issues resolved.

    Reply

  3. This fats and oils chart is really helpful. I’ve been frying in sunflower oil, and I think I need to switch to canola or avocado to help my diarrhea issues.

    Reply

  4. I believe that sunflower oil and canola oil have too much omega 6, which is harmful.
    Only butter, ccoconut oil and extra virgin olive oil have the right profile among different fats. Tthe right fats are essential for us and keep us healthy.

    Reply

    1. Virta Health

      Check out our chart above! We have some other fats that are acceptable, such as beef fat and avocado oil.

      Reply

  5. I’ve been on a keto diet for 2.5 years to help control my diabetes. In the past couple of months i’ve started feeling nauseous after meals. I’ve also had several episodes of diarrhoea and vomiting, together and separately. I’ve started cutting out things that might be causing it e.g. sugar alcohols, maltodextrin. The problem is that even the idea of fat of any kind makes me nauseous. I wonder if anyone has any suggestions? My doctor has run blood tests & a stool test but nothing has come back positive so far.

    Reply

    1. Virta Health

      Hello Miriam! Im happy to hear you went to your doctor for testing. Those symptoms sound like the keto flu. Here are some articles that will help. https://blog.virtahealth.com/keto-flu-how-to-avoid-it/ and https://blog.virtahealth.com/vitamins-supplements-on-keto/ I hope that helps!

      Reply

    2. I have been on keto only 5 months and I find myself in a similar situation. No vomiting but definitely discomfortIn the gut and ( bloated belly ). Always after a meal. I am afraid to abandon keto but I need to figure out what is happening. Best of luck to you and I hope to follow your progress.

      Reply

    3. I started out eating three meals a day on my keto diet. After a couple weeks when my body got used to the diet, I too got sick to the smell of food. I decided to skip my meal. After that I started intermittent fasting and only eating one meal a day. I’m not sure if you can do that with your diabetes but it is worth looking into.

      Reply

  6. I think the GI/diarrhea issues caused by different fats is not taken seriously by most. The MCT oil and bulletproof coffee trend has a lot of people suffering in the morning and not knowing why. Also, I remember Dr. Phinney telling a story about a study he was running where the participants were feeling absolutely gross and weren’t able to eat because of the oil used in the food he was serving (it was chicken or tuna salad made with low-quality mayo full of soybean oil with omega-6 if I remember right).

    Reply

  7. up your fiber and get on a probiotic for your gut -microbiome

    Reply

  8. Some times it can be a simple matter of good hand washing and cleaning the vegetables especially leafy greens in vinegar and water

    Reply

    1. Virta Health

      That’s a great point!

      Reply

  9. The only time that I have experienced diarrhea while living a ketogenic lifestyle has been due to a general sensitivity to sugar alcohols. As a result, I have to limit my intake of foods which contain these substances. Considering foods with sugar alcohols really shouldn’t be eaten in larger quantities/frequently anyway, this benefits my way of eating.

    Reply

    1. Virta Health

      Great point! It’s so important to recognize what foods are supporting us in our journey to better health and what foods may be holding us back from feeling our best.

      Reply

  10. Diarrhea is another possible side effect, especially during the first time on a low-carb diet, as your digestive system may need time to adapt to new way of eating. There are many steps to cure diarrhea, such as drinking plenty of fluids with electrolytes.

    Reply

  11. I’ve been on Keto for a month and have had direrreah the whole time. Is this normal?

    Reply

    1. Virta Health

      We aren’t able to provide direct medical advice through this channel. You may find our blog post on diarrhea helpful, though: https://blog.virtahealth.com/fix-diarrhea-keto/

      Reply

  12. I am tracking my intake and staying under 20% protein. I am only using Monk Fruit sweetener – so no sugar alcohol. & all of the fat in my diet has been cream, butter, lard and some Mayo. I am still experiencing diarrhea. Can I assume it is the mayonnaise? Would it help to switch to an olive oil mayo instead?

    Reply

    1. Virta Health

      I would compare the ingredients in your mayo to the ingredients listed in this post to see if you can identify any that may be problematic. There are some excellent mayos that are made with avocado oil that may be a good option for you.

      Reply

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