Does Fish Oil Cause Gas?


Omega 3 fatty acids are a group of polyunsaturated acids. They are found innature but humans make use of three: ɑ-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). They are popular as it’s beneficial to our health. Interestingly, fish do not produce the fatty acids themselves but it accumulates in their tissues from consuming algae. 

Funnily enough, fish oils are derived from oily fish. It is produced by a variety of methods,the most commonly used method in industry is wet pressing.1 Wet pressing involves 4 stages: fish cooking, pressing, decantation and centrifugation. Examples of fish that contain oil in their soft tissues include: Mackerel, Salmon, Tuna and troutThe oil is often used for cooking like other oils such as olive oil and issought after as it contains omega 3 fatty acids.

Overconsuming can be a bad thing and this can be the case with fish oil. Studies revealed overconsuming of  fish oil might cause atrial fibrillation.2,3 Other side effects are milderHowever, one side effect may be the feeling of being “gassy”. This article will explore fish oils by introducing the function of  omega-3 fatty acids and the detrimental effect of overconsumption.

About fish oil

As previously discussed, fish oils are derived from fish that contain oil in their soft tissues. It is can be sold in oil form or as capsules. 

Omega 3 fatty acid

Fatty acids are essential parts of our diet and makeup triglycerides. Fatty acids consist of a carbon chain attached to a carboxylic acid. The carbon chain can vary in length and contain double bonds. When a double bond is present, the fatty acid is known as unsaturated;when there are several double bonds it is polyunsaturated. Omega-3 fatty acids belong to the polyunsaturated group.

In human bodies, we use three omega-3 fatty acids that can vary in carbon chain length and double bonds. We getEPA and DHA from fish. If we do not take sufficient fatty acids, it might lead to deficiency and put our health at risk. 

EPA and DHA have different molecule structures and also function differently. EPA acts as a precursor for three molecules: prostaglandin-3, thromboxane-3 and leukotriene-6. Prostaglandin-3 inhibits platelet aggregation, thromboxane-3 facilitates platelet aggregation and leukotriene-6 is an inflammatory mediator. Overall, the molecules produced by EPA are key to inflammation. DHA is critical  in maintaining brain function. It is the most abundant fatty acid in the brain and is involved in several processes such as the transport of glycine. Therefore, eating fish and taking supplements of  fish oil is proven to be beneficial to our health.

Benefits of eating fish

Benefits of eating fish include its high protein and the rich omega-3 fatty acids. Before moving on to  health benefits of eating fish and taking fish oil, it should be noted that there is no definitive evidence for these claims. Meta-analyses often find contradictory results.

Cardiovascular - Fish oil has been touted as imperative to cardiac health.However, the research did not show consistent results.. When fish oil is assessed in a population with a history of heart problem, there is no effect on overall heart health and prevention of diseases.4 

Stroke - there is unclear evidence for the effects of fish oil on stroke.5 Other studies state marginal effects of fish oil on stroke by lowering blood pressure and that they should not be used as an alternative to blood pressure medication.6

Cancer - Reviews and meta-analyses find that there is an inconclusive effect on cancer. With the possible exception of breast cancer, evidence suggests that fish oil has no effect on cancer.7,8

Inflammation - There is tentative evidence that fish oil might be beneficial towards inflammation. Types of inflammation can include rheumatoid arthritis.9

Other types of disease - It was also invastigated whether fish oil has an effect on other types of diseases including mental health, Alzheimer’s disease and Crohn’s disease. Various effects are reported, but overall, it is likely that fish oil has little or no effect on these.

Potential side effects from fish oil

There are a few side effects of taking fish oil have been reported, which includes: unpleasant taste, bad breath, bad-smelling sweat, headache and gastrointestinal symptoms. Bloating is a gastrointestinal condition where your stomach feels tight and full which is often caused by a build-up of gas, which can result from food intolerance. Other gastrointestinal symptoms such as diarrhoea and acid reflux will be discussed in the following section.


Diarrhea is a condition which affects the gastrointestinal system and causes the passing of loose, watery stool multiple times a day andcan follow by other symptoms such as cramping. It can be treated with over-the-counter medications such as Pepto-Bismol.  

Acid reflux

Acid reflux is another side effect which can be caused by fish oil. It is caused by acid from the stomach entering the oesophagus and results in a burning sensation in the chest. It can also result in an unpleasant taste in the mouth. If it is serious, a doctor may prescribe a proton pump inhibitor which decreases the amount of acid that the stomach creates.

Tips for reducing gas 

Gas and a feeling of being bloaty will naturally resolve itself, but there are some tips to reduce it. 

  • Exercise: This will help to relieve thegas 
  • Avoid swallowing air when eating by closing your mouth: Air can enter the stomach with food producing the gassy feeling
  • Drink plenty of water
  • Eat smaller and more frequent meals
  • Massaging the stomach area can relieve gas from the stomach.


Fish oil is a supplement that can be readily bought and is sourced from fish. It is believed that omega-3 fatty acids in fish oil have certain health benefits. However, the benefits were not consistently found across studyand vary depending on the disease. In addition, fish oil may cause several side effects. One of these is bloating/being gassy which is caused by a build-up of gas in the stomach. This is an unpleasant side effect but there are several tips to reduce it.

Reference list:

  1. Bonilla-Mendez JR, Hoyos-Concha JL. Methods of extraction, refining and concentration of fish oil as a source of omega-3 fatty acids. Revista Corpoica-Ciencia Y Tecnologia Agropecuaria. 2018;19(3):645-68.
  2. Jia XM, Gao F, Pickett JK, Al Rifai M, Birnbaum Y, Nambi V, et al. Association Between Omega-3 Fatty Acid Treatment and Atrial Fibrillation in Cardiovascular Outcome Trials: A Systematic Review and Meta-Analysis. Cardiovascular Drugs and Therapy. 2021;35(4):793-800.
  3. Gencer B, Djousse L, Al-Ramady OT, Cook NR, Manson JE, Albert CM. Effect of Long-Term Marine-3 Fatty Acids Supplementation on the Risk of Atrial Fibrillation in Randomized Controlled Trials of Cardiovascular Outcomes: A Systematic Review and Meta-Analysis. Circulation. 2021;144(25):1981-90.
  4. European Medicines Agency. Omega-3 acid ethyl esters - containing medicinal products for oral in use in secondary prevention after myocardial infarction. EMA. 2019:328211
  5. Campano CGA, Macleod MJ, Aucott L, Thies F. Marine-derived n-3 fatty acids therapy for stroke. Cochrane Database of Systematic Reviews. 2022(6).
  6. Campbell F, Dickinson HO, Critchley JA, Ford GA, Bradburn M. A systematic review of fish-oil supplements for the prevention and treatment of hypertension. European Journal of Preventive Cardiology. 2013;20(1):107-20.
  7. Heinze VM, Actis AB. Dietary conjugated linoleic acid and long-chain n-3 fatty acids in mammary and prostate cancer protection: a review. International Journal of Food Sciences and Nutrition. 2012;63(1):66-78.
  8. Zheng JS, Hu XJ, Zhao YM, Yang J, Li D. Intake of fish and marine n-3 polyunsaturated fatty acids and risk of breast cancer: meta-analysis of data from 21 independent prospective cohort studies. Bmj-British Medical Journal. 2013;346.
  9. Robinson LE, Mazurak VC. N-3 Polyunsaturated Fatty Acids: Relationship to Inflammation in Healthy Adults and Adults Exhibiting Features of Metabolic Syndrome. Lipids. 2013;48(4):319-32.
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Miles Peter Bremridge

Masters of Science - MSc Neuroscience Student and Neurosoc Chair, The University of Manchester, England

Miles Bremridge is a MSc Neuroscience Student who is working as a Neurosoc UoM Social Secretary at The University of Manchester. He is also an experienced Medical Writer.

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