Fish oil is a dietary supplement rich in omega-3 fatty acids, which have been found to support brain and heart health and improve mood. The two main types of omega-3 found in fish oil are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
While generally safe and well-tolerated, fish oil supplements can cause side effects, especially at higher doses (more than 2 grams per day).
Fish oil supplements can cause your skin, breath, and urine to have a fishy smell. This side effect may be worse in people who tend to sweat more. You can also experience fishy-smelling burps.
Some fish oil supplements tend to have a fishy aftertaste. It’s been reported that freezing your fish oil capsules may slow their breakdown in the stomach, reducing aftertaste.
Some studies suggest that high amounts of fish oil (900 milligrams of EPA and 600 milligrams of DHA or more per day for several weeks) can reduce immune function and may suppress the body’s ability to fight off infections.
However, several other studies have found that omega-3 fatty acids in fish oil can improve immune function.
High doses of fish oil (especially doses over 5 grams per day) can raise the risk of bleeding. Taking fish oil with other medications that increase bleeding, such as blood thinners like Coumadin (warfarin), can further raise this risk.
Fish oil supplements may also cause headaches when taken in high doses. However, other studies have reported that omega-3 fatty acids in fish oil can help prevent or reduce headaches.
Fish oil can cause stomach-related side effects such as diarrhea, stomach pain, and nausea. These symptoms are more common with higher doses of fish oil.
Fish oil can cause heartburn, especially if you are already prone to acid reflux. However, taking fish oil supplements with food may help reduce this side effect.
While fish oil has been found to reduce the risk of heart attack, some studies suggest that regular use of fish oil supplements might raise your risk of atrial fibrillation (a type of irregular heartbeat).
The increased risk of atrial fibrillation may be due to the oxidation of the oil found in fish oil supplements, which can clog your arteries.
Do not take fish oil without first checking with a healthcare professional if you:
- Are allergic to fish
- Have heart disease or a bleeding disorder
- Are pregnant
- Take blood thinners (aspirin or warfarin) or blood pressure-lowering medications
Some ways you can manage fish oil side effects include:
- Take fish oil supplements with food, especially meals high in healthy fats, like avocados
- Divide your dose of fish oil between morning and evening to make it more tolerable
- Store fish oil capsules in the fridge or freeze capsules before use
- Do not exceed the recommended dosages
- Choose brands that make fish oil from smaller fish, such as anchovies and sardines, to minimize mercury exposure
