Fish oil and IBS

Copy of IBS and fish oil supplements.png

Jimmy Lee - Research Dietitian, 21 October 2022

You probably have seen fish oil supplements on the shelves of your local supermarket or pharmacy. Although many of us consume fish oil supplements, have you ever thought of what role fish oil plays in IBS symptom management? 

What is fish oil?

Fish oil is extracted from the tissues of oily fish. Examples of oily fish include, but are not limited to: sardines, salmon, herring and mackerel. 

Fish oil is a rich source of omega-3, a type of ‘good fat’ known as polyunsaturated fats. Specifically, there are three types of omega-3, namely DHA, EPA and ALA. DHA and EPA are the two types of omega-3 that can be found in fish oil.

Omega-3 helps support optimal body function and cell growth. Moreover, the human body cannot synthesise this type of fat. In addition to oily fish, omega-3 can also be found in other sources, such as:

  • Seafood

  • Nuts and seeds

  • Plant oils (flaxseed oil, soybean oil, rapeseed oil)

Some foods, such as yoghurt, may also be fortified with omega-3.

Supplements are another way to receive omega-3 for many individuals. In 2021, the global market value of fish oil supplements was estimated to be over 800 million USD (1). 

The effects of fish oil supplements are often investigated in heart health. Although still an area of research requiring further studies, systematic reviews of multiple clinical trials have indicated their possible benefits in lowering the risk of heart disease events and heart disease related deaths (2-4). 

What role does it play in gut health?

In recent years, there has been emerging evidence investigating the role of omega-3 in optimising gut health. Studies have suggested that omega-3 may support gut health by reducing inflammation and regulating the ratio of ‘good’ and ‘bad’ bacteria in the gut environment (5). 

An observational study in 2017 found an association between omega-3 blood levels and an increased variety of bacteria in the gut (known as gut microbiome diversity) amongst middle-aged and elderly women (6). A larger diversity of microbiota means it can support more health-beneficial functions and build a stronger gut. Lower diversity of gut microbiota is also associated with various diseases. The authors of this study also stated that the anti-inflammatory properties of omega-3 on gut microbiome may be due to the products produced from DHA metabolism.  

Another open-label randomised trial found that omega-3 supplementation (as capsules or as a fish oil-containing drink) increased the number of some short chain fatty acid-producing bacteria amongst healthy individuals (7). Short chain fatty acids are thought to support the wellbeing of the gut and also our immune system. 

A Taiwanese study looking into a female-based Asian population found that blood DHA and omega-3 in IBS patients were lower than controls (8). 

Until now, research on the use of fish oil supplements remains relatively new in gut health. Moreover, there is a lack of complex research to support the use of fish oil supplements in the IBS population. Current IBS clinical guidelines make no mention of using fish oil supplements to treat IBS. 

Pure fish oil supplements are naturally low FODMAP (assuming that they are 100% fish oil with no other additives) and likely safe for IBS patients if you choose to have fish oil supplements for other health benefits. However, until large-scale and high-quality research can warrant the effectiveness of fish oil supplements, we should opt for other evidence-based treatment options to keep IBS symptoms at bay. 


1. Global News Wire. Fish Oil Market Size is projected to reach USD 3.60 Billion by 2030, growing at a CAGR of 6%: Straits Research [internet]. USA: Global News Wire; 2022 [updated 2022 Jun 30, accessed 2022 Oct 21]. Available from:

2. Abdelhamid AS, Brown TJ, Brainard JS, Biswas P, Thorpe GC, Moore HJ, et al. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database of Systematic Reviews. 2020;2020(3).  

3. Rizos EC, Markozannes G, Tsapas A, Mantzoros CS, Ntzani EE. Omega-3 supplementation and cardiovascular disease: Formulation-based systematic review and meta-analysis with trial sequential analysis. Heart. 2020;107(2):150–8.  

4. Hu Y, Hu FB, Manson JAE. Marine omega‐3 supplementation and cardiovascular disease: An updated meta‐analysis of 13 randomized controlled trials involving 127 477 participants. Journal of the American Heart Association. 2019;8(19).  

5. Costantini L, Molinari R, Farinon B, Merendino N. Impact of omega-3 fatty acids on the gut microbiota. International Journal of Molecular Sciences. 2017;18(12):2645.  

6. Menni C, Zierer J, Pallister T, Jackson MA, Long T, Mohney RP, et al. Omega-3 fatty acids correlate with gut microbiome diversity and production of N-carbamylglutamate in middle aged and elderly women. Scientific Reports. 2017;7(1).  

7. Watson H, Mitra S, Croden FC, Taylor M, Wood HM, Perry SL, et al. A randomised trial of the effect of omega-3 polyunsaturated fatty acid supplements on the human intestinal microbiota. Gut. 2017;67(11):1974–83.  

8. Chua CS, Huang S-Y, Cheng C-W, Bai C-H, Hsu C-Y, Chiu H-W, et al. Fatty acid components in Asian female patients with irritable bowel syndrome. Medicine. 2017;96(49).  

Back to all articles
Back to all articles