Soylent, IBS, the low-FODMAP diet, and gut bacteria

Hi gralinnaea,

I personally think it’s better to find a recipe that almost fully removes your symptoms and then follow that up with additions of pre-biotics, then pro-biotics and finally digestive enzymes, each as their own test before combining. This would be in line with the general fodmap diet methology.

The monash university has a seperate section specifically for pre-biotics >

Finally i reviewed your recipe and found some red flags you might want to consider

I hope this feedback could help you change the recipe in such a way that you won’t have any issues anymore.

Thanks Tetsuo,

I appreciate the info. :smile:

The major confusion for now is what to use for carbs, since corn is also potentially problematic. :frowning:

You could run a trial where you replace the masa harina for rice flour, rice is fodmap safe.

I don’t think we should be concerned about Soylent “dependence.” The balance of gut bacteria may change on exclusive Soylent, and some strains may disappear (though it’s more likely they’ll just become very scarce).

But they’ll come back when you get back on other foods. Pretty much nothing you eat is sterile… You’re being inoculated with fresh bacteria from your food and environment all the time. Your system may take days or even weeks to build up and re-stabilize colonies, but it won’t take too long.

It’s not unlike recovering after a necessary course of antibiotics. Or recovering after a fast… This year, I’ve been doing periodic three-day fasts, and my bacteria (which go largely absent during the fast) definitely need to recover when I start eating again and it’s about three days before I’m “normal” again.

Just to add on - whey protein isolate and soy protein isolate is safe on a FODMAP diet, as long as any other ingredients are also safe.

Whey protein concentrate may be safe, but only if it indicates that it’s lactose-free.

The popular NOW Foods whey protein isolate has no other ingredients and is a good, safe base.

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Whey protein isolate should be safe for FODMAP but might not be for IBS, personally a small scoop of whey protein isolate is enough to make me seriously sick.

Also protein powders have never been tested by monash university so we cannot be sure, we know that all of rice is safe, so the protein should be the safest choice.

I’m not really familiar with FODMAP, or “poop transplants” but I was diagnosed with “mild IBS” back in high school and was told it was primarily triggered by caffeine and overeating. I’ve also noticed anything from starbucks which I am sure is a combo of the caffeine with massive amounts of sugar.

About two weeks ago I got my first order of Soylent, one week’s worth. I was so excited! I had tried some DIY but it wasn’t the same. I found that eating Soylent for breakfast and lunch wasn’t just easier but it drastically improved my IBS symptoms. I normally take non-prescription pills and eat yogurt each morning for the pro-biotics to handle my IBS, but after about 2-3 days of my body adjusting to Soylent, I craved Soylent.

I have now signed up for a recurring subscription and cannot wait to try v1.2 that is supposed to have a thicker consistency.

Also, I noticed within the first day of going off Soylent I was more tired and my digestive tract went back to its old tricks. So until I get my next supply it’s back to the pills and yogurt.


I’ve been formally diagnosed with IBS-C (constipation type). I’ve had it my entire life. I normally only have bowel movements maybe once or twice a week. As you can imagine, it’s pretty painful. Over the last year, I’ve been prescribed and recommended all types of medicines, supplements, and diets to help ease my symptoms: magnesium complete, digestive enzymes, probiotics, laxatives, anti-bloating medicines, fiber supplements, gluten-free diet, dairy-free diet, and all of these at the same time (no joke) and found no relief. Last week, my GI doctor told me to consider the dreaded low FODMAP diet.

Luckily, my Soylent 1.4 arrived last week and I’ve been hoping it would help with my symptoms. I’ve been consuming almost nothing but 1.4 since, and I’m amazed. Now I have a bowel movement once daily in the morning like clockwork. Things come easy. I’m not in pain. My abdomen even looks kind of flat now (usually always bloated). The more normal food I eat, the less consistent and pleasant things get, but, so far, Soylent has been a huge success for my IBS. I’m hoping things will get even better with more exercise. Thank you so much, Rob, for making this.


So, my experience may not have been the positive sign that I thought it was. Basically, over the last two weeks that I’ve been on almost exclusively Soylent 1.4, I seem to have developed hypoglycemia. I’m also having symptoms of foul smelling stool which may indicate a potential carbohydrate malabsorption issue. All of this fits well with IBS since people with IBS tend to have issues processing certain carbohydrates. I suspect isomaltulose may be a source of these issues as it’s reportedly incompatible for people with fructose or sucrose intolerances, which I’ve been given a test kit for. I will be going to the doctor soon with this information, and putting a pause on Soylent. I’ve documented my experiences in these threads:

Thank you so much @Tetsuo, this fully addresses what I’ve been trying to find in my internet searching. I’m not concerned about dependency, just don’t. want to be surprised by some amount of FODMAP that could be a problem. Cheers!

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