What’s the best diet for IBS?


Have you just been diagnosed with irritable bowel syndrome (IBS)? If you answered yes, then you may be fervently looking for which type of diet is the best for helping with your IBS symptoms. This post will go over all of the different dietary therapies that may (or may not) be beneficial to those with IBS. It’s important to remember that while some diets have stronger recommendations than others, there is not one perfect IBS diet that will work for every single person. Be sure to weigh the pros and cons of each diet and work with your healthcare provider. Now onto your dietary options!


Specific Triggers

  • High-fat foods: For some people, meals and specific food items that are high in fat may overstimulate the gut. However, there are no studies proving that high-fat foods are or are not a specific trigger for people with IBS.
  • Spicy foods: A food chemical called capsaicin is found in chili peppers and spicy foods made from it. Some people with IBS report increased symptoms, specifically abdominal pain when consuming those foods. The reason may be that people with IBS experience visceral hypersensitivity
  • Alcohol: Alcoholic drinks are considered a gastric irritant as they increase acid in the stomach. Excess alcohol consumption is potentially inflammatory to the lining, resulting in gastritis. When it comes to IBS, alcohol may increase symptoms because it increases gut transit speed. The type and quantity of alcohol may also play a role.
  • Caffeine: Similarly to alcohol, beverages containing caffeine increase gut transit speed as well as increase acid. This may increase symptoms of IBS.


Fiber Changes

There are two different types of fiber, soluble and insoluble. Soluble fiber reduces constipation by providing bulk to your stool, pulling water into the gut, turning into a gel, and producing a softer and easier to pass bowel movement. Insoluble fiber also provides bulk to stool and may speed up transit time. Many foods contain both soluble and insoluble fiber. 

Soluble fiber-rich sources include psyllium husk, oat bran, beans, and chia seeds. Insoluble fiber-rich sources include wheat bran, whole grains, and vegetables like carrots and dark, leafy greens. 

Recent AGA guidelines recommend trying soluble over insoluble fiber for IBS symptoms, specifically soluble fiber that won’t ferment in your gut. Fermentation, while a good thing for most, may increase symptoms in people with IBS. Good sources of poorly fermentable soluble fiber are psyllium husk and chia seeds. 

Elimination Diets

An elimination diet removes specific foods or food groups from your diet due to suspicion of intolerance. Elimination diets are typically not meant to be long-term, and should always be followed by a reintroduction or challenge period. This ensures that you are not unnecessarily eliminating foods or food groups. This type of diet is not without the risk of nutritional deficiencies, so it’s recommended to discuss any big dietary changes like this with your healthcare provider.

  • Dairy-free: A dairy-free diet is when you eliminate all dairy products and any products made from dairy (i.e. cow’s milk). Most studies looking at the effects of dairy and IBS symptoms focus on lactose. Lactose is the sugar in milk (also a FODMAP!) that requires the lactase enzyme to digest it. Over 60% of the population is considered lactose intolerant. Dairy-free may be unnecessarily restrictive as opposed to lactose-free. Since it is typically the lactose in dairy products that cause gastrointestinal issues, it’s a more reasonable recommendation to try lactose-free first.
  • Gluten-free (GF): Gluten is a protein found in wheat, barley, and rye products. People with IBS often find relief from a gluten-free diet. However, this is likely not because they are cutting gluten, but because they are simultaneously reducing or eliminating fructans, a carbohydrate (also, FODMAP) found in many of the same foods. On the other hand, some people do not experience relief from a GF diet. This may be because some GF products contain high-FODMAP ingredients like coconut or soy flour. Some studies have shown benefits for a GF diet with IBS, but most are in favor of a low FODMAP diet. A GF diet may be unnecessarily restrictive.
  • Low FODMAP: The Low FODMAP diet is a three-phase diet where fermentable carbohydrates are eliminated or reduced for a short period of time. The first phase is elimination, the second phase is reintroduction, and the third phase is personalization. Recent ACG guidelines as well as the Canadian Association of Gastroenterology all recommend a limited (2-6 week trial) of the Low FODMAP diet as a first-line dietary treatment. Evidence shows benefit in 3 out of 4 people in terms of IBS symptom management. 

What’s on the internet? (Aka Fad Diets…)

If you google “IBS diet” you may find some websites or anecdotal reports of certain foods and fad diets helping with IBS. There are zero studies looking at the effectiveness of these diets. Popular diets right now include ketogenic (aka keto), intermittent fasting, and juicing. 

The keto diet was initially meant to help control seizures in those with epilepsy. It is extremely low carbohydrate, high in fat, and minimal in protein. Since going more mainstream, the keto diet has been introduced to help with everything from weight loss to IBS. While there is no evidence for IBS, some people may find benefits. This may be due to a reduction in FODMAPs or other trigger foods. We do not know what long-term impact the keto diet may have on your gut microbiota, so take any information you read with a grain of salt!

Intermittent fasting is all about the timing of eating. You fast for a set period (i.e. 16 hours) and then have a window where you can eat (i.e. 8 hours). There are no current studies on IBS and Intermittent fasting. Anecdotal evidence may show benefits for some, while others may feel worse. The frequency or portion sizes consumed during the eating window may play more of a role in symptoms than the actual fasting.

Finally, juicing. Celery juice, specifically, shows zero evidence of any health benefits. Juice fasts may be detrimental to health due to the lack of fiber and protein. However, juice made from fruits and vegetables can act as a supplement to someone’s diet. There just isn’t any evidence that it will help with IBS symptoms. Be sure to take into account that some fruits and vegetables that are high-FODMAP may worsen your symptoms, and discuss this with your healthcare provider.


The Bottom line…

IBS and food triggers are typically very person-specific. Although the Low FODMAP diet has been shown to be effective in 3 out of 4 IBS patients, not all people will have the same triggers within the diet. Be sure to work with an IBS and Low FODMAP-trained Registered Dietitian to ensure that you’re receiving the proper nutrition while making dietary changes. Remember, your clinicians are also there to help you make sense of your symptoms,  including the timing, and to help differentiate between what’s normal vs. what’s abnormal.



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