Among the supplements lining grocery store shelves, you’ve likely come across fish oil. Thanks to its high content of omega-3 fatty acids (found in the diet via fatty fish) for centuries, research links fish oil to health benefits, including better heart health, cognitive function and reduced risk of certain cancers. Like other supplements, it can be confusing to determine whether or not to take fish oil, especially if you do not consume fatty fish regularly. Here’s what you need to know about fish oil before deciding if a supplement is right for you.
Fish oil is derived from the tissues of fatty, oily fish like salmon, mackerel, tuna, anchovies, sardines and trout. Just like these fish, fish oil is rich in omega-3 fatty acids, specifically EPA and DHA. Omega-3 fats are important components in the structure of our cells, especially in the brain and eyes. They’re also an energy source for the body and an anti-inflammatory agent. Health organizations have varied recommendations on omega-3 fats, but the recently updated 2020-2025 Dietary Guidelines recommend adults and children consume fish 2–3 times per week (with one serving equating to 4 ounces). However, most Americans are far from meeting this goal.
The updated guidelines on fish consumption are greater than ever before, and children are included for the first time, likely due to the growing body of research on the benefits of omega-3 fats. The literature tends to favor a few different health categories, where it is thought to have the most benefits: fetal growth and development, cardiovascular health and cognitive function, though various cancers and inflammatory conditions are also being researched.
Because omega-3’s, especially DHA, is an important component in the structure of brain cells, it has been hypothesized that fish oil may be protective against cognitive decline and promote overall brain health. Several studies on this topic have mixed findings, ranging from a reduced risk of Alzheimer’s disease and dementia among individuals who supplemented with DHA versus those who did not, to several reviews and meta-analyses showing omega-3 supplementation did not significantly affect cognitive function.
Fish oil is commonly thought to have a cardio-protective effect, but the research has also been somewhat mixed. Studies have found a reduced risk of cardiovascular death and significant reductions in rates of heart attack and heart disease in individuals taking fish oil supplements compared to those who did not. However, a meta-analysis found omega-3 supplementation did not reduce the risk of heart attack, stroke or cardiovascular death. Another study using high-dose omega-3 supplementation (available only by prescription) found individuals taking the supplement had a significantly lower risk of stroke. Prescription, high-dose omega-3 supplements have also been found to reduce triglycerides in individuals with high levels.
Omega-3 fatty acids, especially DHA, are essential for fetal growth and development because they play such an important role in the structure of cells in the brain and eye. The current dietary guidelines recommend pregnant women consume 8–12 ounces of low-mercury, high-DHA/EPA seafood per week, such as salmon, sardines and trout. This equates to around 200–300mg of DHA, and the recommendation for breastfeeding women is similar. Studies are mixed and inconclusive on improvements in a child’s cognitive function, language and conceptualization whose mothers were supplemented with omega-3’s when pregnant. However, omega-3 supplementation may help reduce the risk of low birth weight. Most prenatal vitamins contain DHA.
Fish oil is also known to produce molecules that work to reduce inflammation in the body, which may help reduce the risk of chronic disease and even some cancers. It may also be beneficial to help reduce painful symptoms of inflammatory diseases such as rheumatoid arthritis.
If you like and consume fatty fish regularly (2–3 times per week), fish oil supplementation isn’t typically necessary. You can also get omega-3’s from other sources such as grass-fed beef and free-range eggs.
Supplementing with fish oil can help those who dislike the taste of fatty fish, but it’s not strictly necessary if you’re eating a well-balanced diet. A good place to start is by tracking your intake with an app like MyFitnessPal so you can get a sense of the types of fats you’re consuming.
If you’re thinking of supplementing, always discuss it with your dietitian or doctor and make sure you’re purchasing from a reputable brand that does third-party testing. It’s also a good idea to store the bottle in the refrigerator to slow oxidation. Avoid buying large bottles of capsules or liquids. While the price per capsule may be enticing, buying in bulk could lead to accidental oxidation — smaller bottles are open for, and used up, in a shorter time.
Ultimately, the best way to reap the most benefits from fish oil is to combine your intake (either via supplementation or fish) with a diet rich in fruits, vegetables, whole grains, beans and legumes.
Originally published August 2014, updated with new information
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