Does Oatmeal Cause Gas and Bloating?

7 Ways Oatmeal Can Cause Gas and Bloating (Directly/Indirectly)

A question I hear often in my private nutrition practice is: “Does oatmeal cause gas and bloating?”

In short, yes, it’s possible – whether directly, or indirectly. However, this isn’t the case for everyone.  If this is happening, it’s usually a sign of something deeper going on.

Whether or not oatmeal could be making you gassy and bloated (and why) depends on certain factors related to your unique biochemical individuality, including but not limited to your:

  • Gut microbiome
  • Gut lining
  • Immune system
  • Genetics
  • Intestinal brush border enzyme production

From a holistic perspective, there are also some other angles to consider, such as:

  • The amount of oatmeal you’re eating at one time
  • The type of oatmeal you’re eating
  • Oatmeal add-ons (think: nuts, fruit, milk, sugars/sweeteners, etc.)
  • What else you’re eating/drinking alongside your bowl of oatmeal 

Now, let’s dive deeper into each of these possible ways oatmeal can make you gassy – and what you can do about it!

Disclaimer:  This article was written for education purposes and shouldn’t replace 1-1 medical nutrition advice from your doctor and a gut health dietitian nutritionist.

Affiliate disclosure:  This post contains affiliate links*.  I may earn a commission on qualifying purchases, at no extra cost to you!

Gas and bloating – what’s normal, and what isn’t

Before we dive into oatmeal, let’s quickly make sure we’re on the same page about what it means to experience gas and bloating.


Gas means there’s some kind of fermentation happening in your gut… and the bi-product is odorous air (with or without noise) which will need to get released via burping or farting.  

(Unpleasant to think about / talk about… but hey, it’s more common than you may realize! Take it from a gut health dietitian.) 😉

Occasional gas is normal, especially after eating notoriously “gassy foods” like beans or brussel sprouts.

But while frequent gas (especially the smelly kind) may be common – it’s NOT normal! It means something is out of alignment in your digestive system, such as digestive insufficiency and/or a gut microbial imbalance.


My clients have described bloating as a “basketball belly” and feeling like they’re “6 months pregnant.”  (Their words, not mine!)

Bloating can happen with or without symptoms of gas.  Again, occasional bloating (especially after a large meal) is normal, but daily bloating (especially after eating) is a sign that something in your digestive system is off. 

It’s usually caused by a digestive insufficiency, microbial imbalance, and/or gut inflammation.

In my clinical practice, I’ve noticed that 99% of the time, gas and bloating seem to get triggered by certain foods (or in more severe cases, all food).

Enter… oatmeal! 

When does oatmeal cause gas and bloating? (7 considerations)

Based on my experience as a holistic and functional gut health dietitian and as a former IBS sufferer, some of the most common but little-known ways oatmeal may cause gas and bloating (directly or indirectly) include:

  1. Fiber/roughage
  2. Gluten/wheat cross-contamination (if reactive to gluten/wheat)
  3. Starch intolerance
  4. Too-large portions
  5. FODMAP stacking
  6. Reactive flavorings/add-ons
  7. Reacting to accompanying foods

Note that some considerations aren’t directly related to oatmeal… but these considerations may help explain how oatmeal could be indirectly causing gas, if none of the other reasons apply to you!  (As always, please take what you need, and leave the rest.)


Oatmeal is high in fiber.  Just 1/2 cup of rolled oats (before cooking) usually contains close to ~5-6 grams of fiber per serving.  

Fiber is a type of indigestible “roughage” which adds bulk to stool, reducing transit time and helping in regularity.

Generally, a healthy adult needs between ~20 to 38 grams of fiber per day.

Fiber and fluids: foundations

On a foundational level, not drinking enough fluids while eating fiber-rich foods can lead to symptoms of gas and bloating.

That’s because fiber needs fluids to help flush it through and out of your digestive tract.

What you can do

Are you drinking at least 8 to 10 cups of fluid per day? If not, I’d give that a try!

But if this doesn’t help, there may be something deeper going on.

Fiber/roughage intolerance

However, in cases of a fiber intolerance, your body can’t tolerate fiber due to an underlying digestive disorder or gut imbalance.

(I’m a huge advocate of uncovering the root causes of your gut issues, so you can take more informed action!)

Based on my experience in private practice, a fiber intolerance is most often caused by:

  1. Small intestinal bacterial overgrowth (SIBO) and/or
  2. Inflammatory bowel disease (IBD)

(Yes, you read that right… it’s possible to have BOTH SIBO and IBD in unfortunate, complex cases!)

SIBO-induced fiber intolerance

If you have SIBO, you may likely feel worse eating high fiber, high FODMAP foods.  

You may also notice that high-fiber “functional foods” like chia seeds, ground flax seeds, and psyllium husks (which are supposed to be “healthy” make you very bloated and uncomfortable.

This is because the microbes in your intestines are consuming the fibers, which produces intestinal gas such as methane or hydrogen… even if the fiber is from low FODMAP foods.  (When you have SIBO, everything and anything you eat can make you bloated/gassy unfortunately, until the microbial overgrowth is eradicated!)

The best way to know for sure is to consult your GI doctor about running a SIBO breath test (so you can take more informed action with a targeted approach), and to work with a SIBO-trained gut health dietitian to help you look for patterns via a detailed food-symptom journal.

But note that not all fiber intolerances are caused by SIBO.

Enter:  Inflammatory bowel disease (IBD).

IBD-induced fiber intolerance

Inflammatory bowel diseases (IBD) such as Crohn’s, celiac disease, colitis, and diverticulitis are caused by immune system imbalances.  

Left unchecked, these conditions will cause a very inflamed gut lining, because an autoimmune reaction causes your intestinal cells to attack themselves.

When your gut lining is inflamed, this makes it difficult to digest and absorb roughage – aka high fiber foods.

In these cases, you may notice that not just oatmeal, but also other high-fiber foods like raw veggies (lettuce, salads, carrots, celery), fresh fruit with skins, and beans also seem to trigger gas and bloating – usually alongside diarrhea and abdominal pain.

The best way to know for sure if you suspect IBD-induced fiber intolerance is to consult your GI doctor about a colonoscopy, or at the very least, a calprotectin test.  

  • Calprotectin is an inflammatory marker that usually runs high in cases of IBD.

What you can do about it

If you’ve determined you have an intolerance to the fiber and roughage in oatmeal, the next step is to figure out what’s causing it (if you haven’t already) – and treat/address the root cause.

For example, in cases of SIBO, people usually feel better on a low fiber + low FODMAP diet, and also need antibiotics or herbal antimicrobials (alongside other supportive supplement interventions) to properly eradicate the microbial overgrowth.  (You can’t starve SIBO!)

In cases of inflammatory bowel disease, a low fiber, low residue diet may need to be layered with another type of dietary intervention such as the LEAP diet, a gluten free diet (in cases of celiac disease), or perhaps another type of IBS diet such as Specific Carbohydrate, Gut and Psychology Syndrome, or Paleo – to address your autoimmune issues.

Recommended reading:  What’s the Best IBS Diet for You? 

When in doubt, keep a food-symptom diary which can help you to more easily pinpoint the food triggers of unwanted symptoms.  But make sure to also consult a gut health dietitian who specializes in what you need, for clinical support and customized guidance.

But the buck doesn’t stop with food! Gut repair, microbial rebalancing and nervous system regulation are not optional when it comes to addressing and resolving gut issues long-term.

If you’d like more details on what a holistic, comprehensive gut repair protocol looks like step-by-step, I highly recommend my online course, the Complete Gut Repair Roadmap.

The Complete Gut Repair Roadmap Learn More

Gluten/wheat cross-contamination 

Unless you’re buying gluten free oatmeal, you may be consuming oats that have been cross-contaminated with wheat, a grain that contains gluten.

While this isn’t inherently bad, it could be an issue if you have celiac disease or even a non-celiac wheat sensitivity.

What you can do about it

If you have or suspect an issue with wheat/gluten, consider switching to gluten free oats and see if this fixes the gas/bloating reaction.

If you notice you feel better, consider consulting your doctor about ruling out celiac disease (BEFORE going gluten free) so you don’t leave that unchecked!

Recommended reading:  Gluten vs. Wheat – What’s the Difference?

But if gluten/wheat cross-contamination isn’t the issue, keep reading.

Starch intolerance

Oatmeal is a type of whole grain which provides us with carbohydrates in the form of starch.

This isn’t inherently bad or unhealthy… unless you happen to have a starch intolerance!

A starch intolerance means your body isn’t making enough of the enzymes that break down maltose (the sugar which makes up starch).

When you eat any kind of starch (including oatmeal) in these cases, you’ll likely feel gassy and bloated, usually alongside diarrhea, abdominal cramping, and in some cases, nauseous.

Of course, keeping a detailed food-symptom journal and paying special attention to how you feel when you eat other starchy foods (like bread, crackers, potatoes, and rice) can quickly help to rule out whether or not your oatmeal-induced gas/bloating is caused by a starch intolerance!

For clinical supervision and guidance, consult with a CSID-informed gastroenterologist to help you determine whether or not you have one of the following conditions (which cause starch and sucrose intolerance):

  1. Congenital sucrase-isomaltase deficiency (CSID)
  2. Acquired sucrase-isomaltase deficiency (ASID)

What you can do about it

If you DO have an intolerance to starch (and/or sucrose), I highly recommend the following resources:

However, if this isn’t relevant, keep reading!

Too much oatmeal

Food for thought:  Are you eating oatmeal at breakfast, before your hunger cues start kicking in?  And how much oatmeal are you eating at one time?  

Believe it or not, eating when you’re not hungry, and/or eating too much of anything at given time (including oatmeal) relative to how much your body needs, can most definitely cause gas and/or bloating.

That’s because your digestive secretions will max out at a certain point.  

The rest of the undigested food (in this case, oatmeal) will end up getting fermented by the microbes in your gut. They will have a feast, and the bi-product of this is – you guessed it – gas (and bloating)!

What you can do

If you suspect you’re eating too much oatmeal relative to what your body is ready for at any given time, consider waiting until the hunger cues start kicking in.  (Think: a slight growl and slightly empty feeling in your stomach – but not too much.)

It may also be worth consulting an expert for support with mindful eating.

But another factor to consider is called “FODMAP stacking”.

FODMAP stacking 

While oatmeal is low FODMAP in portions of 1/2 cup (before cooking it) or less, exceeding a low FODMAP serving size of some low FODMAP foods (including oatmeal) is referred to by Monash University (the leading authority in FODMAPs) as “FODMAP stacking”.

If you’re among the estimated ~40 to 80% of IBS sufferers who feels better on a low FODMAP diet, consider keeping your portions of oatmeal to the Monash-approved serving size of 1/2 cup (measured before cooking), or less.

In this case, I highly recommend adding fats and proteins to have alongside your oatmeal, to help you feel more satiated and sustained for longer.

But there’s more to consider!  Your gas/bloating could potentially be triggered by something else you’re adding to your bowl of oatmeal.

Oatmeal flavorings/add-on’s

What kind of oatmeal are you buying, and do you add anything special to doctor it up?

Think: milk, fruit, honey, nuts, etc.  (As a reminder, none of these types of foods are inherently bad, but they all have the potential to cause gas and bloating!)

We don’t have time or space to open Pandora’s box here, but it’s always good to remember that you could be reacting to something else that you’re adding to your oatmeal. 😉


Okay, so you’ve determined that you aren’t reacting to the fiber, gluten cross-contamination, starch, or FODMAPs in oatmeal, and it isn’t anything you’ve been adding to it.

Have you considered you could be getting gassy from something else that you like to have with your oatmeal?

Think: a cup of coffee/tea (or something you add to it), a glass of milk, etc.

Again, the possibilities are endless, and this will vary depending on a lot of factors.  I just wanted to make you aware of this, since we often don’t know what we don’t know!

Recommended reading:

Frequently asked questions (FAQ’s)

Is oatmeal low FODMAP?

It depends! A Monash-approved portion of low FODMAP portion of oatmeal is ~1/2 cup rolled oats, before cooking.

(Read more about how to enjoy low FODMAP oatmeal here.)

What’s a good portion of oatmeal?

Generally, a low FODMAP portion of oatmeal is 1/2 cup rolled oats before cooking.  Sticking to this portion of oatmeal means you’re less likely to experience symptoms of gas and bloating, unless there are other reasons for your symptoms.

While this may not feel very filling by itself, keep in mind a balanced breakfast should also include some fruit, healthy fat, and protein for sustenance.

Is oatmeal gluten free?

It depends!  Some, but not all types of oats are gluten free, depending on whether or not they’ve been cross-contaminated with wheat (a grain that contains gluten).

Make sure you’re purchasing certified gluten free oatmeal if you need to avoid cross contamination.

Related articles & resources

Final thoughts

As a quick recap, there are lots of possible reasons oatmeal can cause gas and/or bloating – whether directly or indirectly.

Some factors to consider include a possible fiber intolerance (usually related to SIBO and/or IBD), gluten/wheat cross-contamination, starch intolerance (caused by a sucrase-isomaltase deficiency), eating too much oatmeal, FODMAP stacking, potential reactive add-ins, and oatmeal accompaniments.

Remember, as always, to consider keeping an IBS food diary* and consult with a doctor and registered dietitian 1-1 to crack your code faster. 

Next steps

Clearly there’s lots to talk about! And gut health is SO incredibly important. 

If you’d like to stay in touch and learn more about how to support your gut health holistically, make sure to download a copy of my free gut health nutrition PDF guide: 5 Common Diet Mistakes to Avoid On Your Gut-Healing Journey!

Free Download - 5 Diet Mistakes to Avoid When Healing Your Gut - by Jenna Volpe RDN LD CLT

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