EFA supplements provide essential fatty acids, the two fats your body cannot produce on its own: linoleic acid (an omega-6) and alpha-linolenic acid (an omega-3). Because your cells need these fats but have no way to manufacture them, they must come from food or supplements. Most EFA products on the market focus on omega-3s, though some also include omega-6 fatty acids like gamma-linolenic acid (GLA). They come in several forms, from fish oil capsules to algae-based softgels to plant seed oils.
Why These Fats Are Called “Essential”
The word “essential” in nutrition has a specific meaning: your body requires the nutrient but lacks the enzymes to build it from scratch. Only two fatty acids meet that definition. Linoleic acid is the parent omega-6, and alpha-linolenic acid (ALA) is the parent omega-3. Every other fatty acid your body needs in these families can, in theory, be built from these two starting materials.
In practice, that conversion is poor. Your liver can turn ALA into longer-chain omega-3s like EPA and DHA, but reported conversion rates are less than 15%. This is why many people supplement with EPA and DHA directly rather than relying on ALA alone. Similarly, some people have difficulty converting linoleic acid into GLA, particularly those with diabetes, which is one reason GLA supplements exist.
The Main Types of EFA Supplements
Omega-3 Supplements
These are by far the most common EFA supplements. They typically supply three forms of omega-3:
- ALA: Found in flaxseed oil, chia seed oil, and walnut oil supplements. It’s plant-based but converts poorly to the longer-chain forms your brain and heart rely on most.
- EPA (eicosapentaenoic acid): A 20-carbon omega-3 involved in producing signaling molecules that regulate inflammation and blood vessel function. Sourced mainly from fatty fish and krill.
- DHA (docosahexaenoic acid): A 22-carbon omega-3 that is the predominant fatty acid in the brain and retina. Critical during pregnancy for fetal brain development, and linked to cognitive preservation in older adults.
Fish oil is the classic delivery form, but krill oil and algae oil are also widely available. Algae oil is worth noting for vegetarians: it tends to deliver a higher proportion of DHA relative to EPA. In one comparison, algae oil capsules provided a 1:3 EPA-to-DHA ratio (164 mg EPA and 443 mg DHA per capsule), while fish oil capsules provided a 3:2 ratio (289 mg EPA and 205 mg DHA per capsule). Both are bioavailable, so the choice depends on your dietary preferences and which fatty acid you want to emphasize.
Omega-6 Supplements
Most Western diets already supply plenty of omega-6 from cooking oils, nuts, seeds, and eggs. For this reason, standalone omega-6 supplements are less common. The exception is GLA, which comes from evening primrose oil, borage oil, and black currant seed oil. GLA has anti-inflammatory and immune-modulating properties, and supplementation can be particularly helpful for people whose bodies struggle to produce it from dietary linoleic acid, including those with diabetic neuropathy.
Combination EFA Blends
Some products market themselves as “complete EFA” formulas, combining omega-3, omega-6, and sometimes omega-9 fatty acids in a single capsule. Omega-9 fats (like oleic acid in olive oil) are not technically essential because your body can make them, so their inclusion is more of a marketing choice than a nutritional necessity.
Heart and Brain Benefits
The strongest evidence for EFA supplementation centers on omega-3s and cardiovascular health. A large meta-analysis of over 149,000 participants found that omega-3 supplementation reduced the risk of cardiovascular death by 7%, non-fatal heart attack by 13%, and coronary heart disease events by 9%. EPA-only supplements showed even larger reductions: a 28% lower risk of non-fatal heart attack and a 27% reduction in coronary heart disease events compared to EPA-plus-DHA combinations.
For the brain, DHA plays the central role. It supports the structure of cell membranes in nerve tissue, influences neurotransmitter signaling, and helps regulate neuroinflammation. One study of elderly adults found that those with the highest blood levels of DHA had a 47% lower risk of developing dementia compared to those with lower levels. In people already diagnosed with Alzheimer’s disease, higher plasma DHA was associated with slower cognitive decline. These findings don’t prove supplementation alone prevents dementia, but they do suggest that maintaining adequate DHA levels matters for long-term brain health.
How Much You Need
Recommended intakes vary by organization, but the general range is consistent. The American Heart Association recommends about 500 mg of combined EPA and DHA per day for the general population, equivalent to eating oily fish twice a week. For people with existing cardiovascular disease, the recommendation rises to roughly 1,000 mg per day. The World Health Organization sets a broader range of 250 mg to 2,000 mg per day of EPA plus DHA.
If you eat salmon, mackerel, sardines, or herring regularly, you may already be meeting these targets through food. Supplements are most useful for people who rarely eat fish, follow a vegetarian or vegan diet, or have a specific health reason to increase their intake.
The Omega-6 to Omega-3 Ratio
Your body uses omega-6 and omega-3 fatty acids in competing pathways. When omega-6 intake is disproportionately high, it promotes more inflammatory signaling. Modern Western diets tend to deliver far more omega-6 than omega-3, which has been linked to higher rates of cardiovascular disease, cancer, and autoimmune conditions. Research on evolutionary diets and brain composition suggests an ideal omega-6 to omega-3 ratio somewhere between 1:1 and 2:1, while a ratio of 3:1 to 4:1 may still offer meaningful disease prevention compared to the current Western norm.
For most people, the practical takeaway is not to add more omega-6 through supplements but to increase omega-3 intake and reduce excess omega-6 from processed seed oils. This naturally shifts the ratio in a healthier direction.
Side Effects and Interactions
EFA supplements are generally well tolerated. The most common complaints with fish oil are fishy aftertaste, mild nausea, and digestive discomfort, all of which tend to improve when capsules are taken with meals. Omega-3s can extend the time it takes for a cut to stop bleeding, which matters if you take blood thinners or nonsteroidal anti-inflammatory drugs. If you’re on anticoagulant medication, talk to your prescriber before starting an omega-3 supplement. People with fish or shellfish allergies should opt for algae-based products instead.
Choosing a Quality Supplement
Not all EFA supplements are created equal. Fish oils are prone to oxidation, which produces rancid byproducts that may reduce benefits and cause more side effects. International voluntary standards set maximum limits for oxidation markers: peroxide values should stay at or below 5 mEq/kg, and total oxidation (TOTOX) values should not exceed 26. Some products on North American shelves exceed these limits, so choosing a brand that tests against these standards or carries third-party certification adds a layer of assurance.
Beyond freshness, check the actual EPA and DHA content per serving, not just the total “fish oil” amount. A 1,000 mg fish oil capsule might contain only 300 mg of combined EPA and DHA, with the rest being other fats. Concentrated formulas deliver more active omega-3s per capsule, meaning fewer pills to reach your target dose. Algae oil supplements are a reliable alternative that avoids concerns about ocean contaminants and is suitable for plant-based diets.