Fish oil, commonly recognized for its omega-3 fatty acids, is one of the most sought-after dietary supplements available today. Promoted for its numerous health benefits—including heart protection, mood enhancement, and anti-inflammatory properties—it’s essential to examine the scientific basis for these claims and determine when fish oil supplements might be appropriate.
A Long History
The use of fish oils dates back for centuries.
Interest in their health benefits surged in the 1970s when researchers exploring Inuit diets identified omega-3 fatty acids and recognized their protective effects on heart health.
By the 1980s, fish oil capsules became popular as a convenient way to obtain these beneficial fats.
What’s in Fish Oil?
Fish oil is derived from oily fish, such as salmon, sardines, tuna, herring, and mackerel. It is particularly rich in omega-3 polyunsaturated fatty acids (PUFAs), primarily eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
These omega-3s play a vital role in cellular functions. Each cell in our body is encapsulated by a flexible cell membrane, which serves as a protective barrier. It maintains the integrity of the cell’s contents, regulates the movement of substances in and out, and facilitates communication between cells.
Though omega-3s do not form the membrane itself, they integrate into the membrane structure, contributing to its fluidity and flexibility. This is particularly crucial for tissues that depend on rapid and precise signaling, such as those in the brain and eyes.
As our bodies cannot produce sufficient omega-3s, we must obtain them through our diet or supplements.
How Are Fish Oil Supplements Made?
After fish are harvested, their tissues are cooked and pressed to extract the oil. This crude oil undergoes purification and refining processes to eliminate impurities, including harmful heavy metals like copper, iron, and mercury.
During production, the oil may be concentrated to enhance its EPA and DHA content.
The refined oil is then encapsulated into soft gels or sold as liquid oil. Some supplements are additionally treated to minimize odors or the characteristic “fishy” aftertaste.
Fish Oil and Heart Health
Omega-3 fatty acids are most renowned for their benefits to heart health, particularly in lowering triglyceride levels—a type of fat in the bloodstream that, when elevated, can increase the risk of heart disease.
A 2023 study that reviewed 90 clinical trials involving over 72,000 participants highlighted a nearly linear relationship between dosage and effect. However, it’s important to note that larger doses did not always equate to better outcomes. A combination of over 2 grams per day of EPA and DHA was found necessary to significantly reduce triglycerides (by 15% to 30%), especially in individuals with pre-existing heart conditions or high triglyceride levels.
When considering fish oil supplements, it’s vital to read labels carefully. For instance, a “1,000 mg” fish oil capsule typically refers to the total oil weight, not the active omega-3 content. Most standard capsules contain only about 300 mg of combined EPA and DHA, with the remaining weight made up of other fats.
At lower doses, changes in blood lipids were modest. This analysis also suggested that low-dose fish oil might slightly raise LDL or “bad” cholesterol levels while having minimal impact on triglycerides.
A 2018 trial examined a high-strength purified EPA product (4 grams per day) in individuals already on statins for cholesterol management. Over five years, this intervention prevented one major cardiac event (such as a heart attack or stroke) for every 21 individuals treated. However, this was a prescription-only, pharmaceutical-grade EPA, rather than a standard fish-oil capsule.
In Australia, fish oils can be found in pharmacies, health food stores, and supermarkets. Some concentrated formulations are available as “practitioner-only” supplements through healthcare professionals.
The same purified EPA used in the 2018 trial is now accessible in Australia under the name Vazkepa, a prescription-only medication. This product was included in the Pharmaceutical Benefits Scheme (PBS) in October 2024, enhancing access for those at high risk.
However, for otherwise healthy individuals, the evidence supporting the use of standard fish oil supplements for heart attack or stroke prevention is considerably less robust.
What About Arthritis and Joint Pain?
Fish oil exhibits mild anti-inflammatory properties.
For those suffering from inflammatory arthritis (e.g., rheumatoid arthritis), omega-3 fatty acids can help alleviate joint tenderness and morning stiffness.
However, these benefits typically require consistent higher doses, around 2.7g of combined EPA and DHA daily, which is roughly equivalent to taking about nine standard 1,000mg fish oil capsules for a minimum of eight to 12 weeks.
Can Fish Oil Improve Mood?
Some research indicates that omega-3s, particularly those higher in EPA, may help alleviate symptoms of clinical depression when taken in conjunction with antidepressants.
A 2019 review encompassing 26 trials and over 2,000 participants reported minor overall benefits, mainly for EPA-rich formulations with doses up to approximately 1 gram per day. In contrast, products containing only DHA did not demonstrate significant effects.
However, fish oil should not be seen as a universal mood enhancer. For individuals without a diagnosis of depression, omega-3 supplements have not been proven to consistently improve mood or act as a preventative measure for depression.
How Much Can You Take?
For most individuals, fish oil is generally safe.
Common side effects may include a fishy aftertaste, mild nausea, and diarrhea. Consuming capsules alongside food or opting for odourless formulations can mitigate these effects.
Prescription-strength products, such as Vazkepa (high-dose EPA), are also well tolerated but can slightly increase the risk of irregular heartbeat (atrial fibrillation) and bleeding.
For most adults, a daily intake of up to 3 grams of combined EPA and DHA from supplements is considered safe.
Higher doses intended for specific medical conditions should be monitored by a healthcare professional.
So, Should You Take It?
The Heart Foundation recommends that Australians consume two to three servings of oily fish weekly, which would provide roughly 250–500 mg of EPA and DHA daily.
If fish is absent from your diet, a fish oil supplement (or algal oil for vegetarians or vegans) can help you meet your omega-3 requirements.
For those with heart disease (especially with high triglycerides) or inflammatory arthritis, fish oil may offer added benefits. However, it’s essential to consider the dosage and type of product, so consulting a healthcare professional is advisable.
Ultimately, for most individuals, consuming two to three servings of oily fish each week remains the most straightforward, safe, and nutritious method to obtain omega-3s.
Mary Bushell is a Clinical Associate Professor in Pharmacy at the University of Canberra. Find Mary on X @mary_bushell
A version of this article was originally posted at Conversation and has been reposted here with permission. Any reposting should credit the original author and provide links to both the GLP and the original article. Find Conversation on X @ConversationUS
