September 2026

Omega-3: What It Actually Does, and Whether You Need to Supplement

Fish oil has sat on supplement shelves for decades, but omega-3 conversation has picked up considerably in recent years, partly driven by growing interest in anti-inflammatory eating and partly by genuinely accumulating research. Worth separating, though: what's well-established, what's promising but still developing, and where an actual gap might exist for you personally.

What omega-3 actually is

Omega-3 refers to a family of essential fatty acids, meaning the body can't produce them itself and they must come from diet or supplementation. The three most relevant forms are ALA (found in plant sources like flaxseed and walnuts), and EPA and DHA (found primarily in fatty fish and algae), with EPA and DHA generally considered more biologically active and more directly linked to most of the benefits associated with omega-3 intake. The body can convert some ALA into EPA and DHA, but this conversion is quite inefficient, which is a significant part of why plant-only omega-3 sources don't provide an equivalent effect to marine sources.

What the evidence actually supports

Omega-3, particularly EPA and DHA, has a well-established role in cardiovascular health, with research supporting benefits for triglyceride levels and general heart health as part of an overall healthy diet. There's also a meaningful and growing evidence base around anti-inflammatory effects more broadly, which is part of why omega-3 gets mentioned frequently alongside joint health and general inflammation-related conversations, alongside supportive evidence for brain health and eye health, given DHA's role as a structural component of both.

Where the evidence is more preliminary

Areas like mood, cognitive ageing, and specific inflammatory conditions show promising associations in research, but the evidence in these areas is generally less conclusive than the cardiovascular research, and effects, where present, tend to be modest rather than dramatic. This is a case where the underlying interest is reasonable, but the confidence with which some of these benefits get marketed online outpaces what the research currently, clearly supports.

Who's most likely to be genuinely low

People who eat little to no oily fish are the most obvious group, since Western diets in general tend to run fairly low in omega-3 relative to omega-6 fatty acids (found abundantly in many vegetable oils and processed foods), and this ratio imbalance is itself a point of ongoing research interest. Vegetarians and vegans are particularly likely to fall short of EPA and DHA specifically, since reliable dietary sources are almost exclusively marine-based, with algae-based supplements being the main non-fish alternative.

Food sources vs supplementation

Oily fish, salmon, mackerel, sardines, and similar, remain the most direct and well-evidenced dietary source of EPA and DHA, with most guidelines suggesting roughly two serves a week as a reasonable target for general health. For anyone not meeting this regularly through food, supplementation is a reasonable way to help close the gap, though quality varies considerably between products, and checking for third-party purity testing (given concerns about contaminants like mercury in some fish oil sources) is worth doing when choosing a specific product.

Practical considerations

Fish oil supplements are generally well tolerated, though mild digestive side effects (a fishy aftertaste, mild nausea) are common and often improve by taking the supplement with food. Anyone on blood-thinning medication should discuss omega-3 supplementation with their doctor first, since higher doses can have a mild blood-thinning effect of their own.

The bottom line

Omega-3, particularly EPA and DHA from marine sources, has solid evidence behind it for cardiovascular health, with promising but still-developing evidence in several other areas. Regular oily fish intake is the most well-evidenced way to get it, and supplementation is a reasonable option for anyone not eating fish regularly, particularly vegetarians, vegans, and those who simply don't eat much fish.

General nutrition information, not individual dietary advice. If you're on blood-thinning medication or have other health conditions, speak with your doctor before starting omega-3 supplementation.