You can get omega-3 fatty acids without eating fish by combining two strategies: eating plant foods rich in ALA (the plant form of omega-3) and, if you want the same types found in fish, taking an algae-based supplement. Each approach has trade-offs worth understanding, because not all omega-3s work the same way in your body.
The Three Types of Omega-3s
Omega-3 isn’t a single nutrient. There are three main forms: ALA, EPA, and DHA. Fish and seafood provide EPA and DHA directly, which are the forms your body uses for brain function, heart health, and controlling inflammation. Plants provide ALA, which your body can partially convert into EPA and DHA, but the conversion is inefficient.
In healthy young men, roughly 8% of dietary ALA converts to EPA and somewhere between 0% and 4% converts to DHA. Women of reproductive age convert more efficiently: about 21% to EPA and 9% to DHA, likely due to the influence of estrogen on the conversion enzymes. This means that while plant foods are excellent sources of ALA, you’d need to eat a lot of them to match the EPA and DHA you’d get from a serving of salmon.
Best Plant Sources of ALA
A handful of everyday foods deliver significant amounts of ALA per serving. The top three, based on NIH data:
- Chia seeds (1 ounce): 5.06 g ALA
- English walnuts (1 ounce): 2.57 g ALA
- Whole flaxseeds (1 tablespoon): 2.35 g ALA
To put these numbers in perspective, the adequate intake for ALA is 1.1 g per day for women and 1.6 g per day for men. A single tablespoon of flaxseeds covers a full day’s requirement and then some. Hemp seeds, canola oil, soy products, and leafy greens like Brussels sprouts also contribute smaller amounts.
One important detail with flaxseeds: whole seeds can pass through your digestive system intact. Ground flaxseed (or flaxseed meal) is far more useful because your body can actually access the fats inside. Store it in the refrigerator or freezer, since the oils oxidize quickly once the seeds are ground.
How to Use These Foods Daily
The easiest approach is to build these ingredients into meals you already eat. Stir ground flaxseed into oatmeal, yogurt, or smoothies. Toss walnuts into salads or eat them as a snack. Add chia seeds to overnight oats or blend them into dressings.
Be careful with heat. Flaxseed oil is particularly fragile. Research shows that heating it causes significant breakdown of its polyunsaturated fats, with measurable degradation starting around 120°C (250°F) and accelerating at higher temperatures. The oxidation produces compounds that not only lose nutritional value but can be harmful. Use flaxseed oil as a finishing oil on cooked dishes, in salad dressings, or drizzled over toast. Never use it for frying or sautéing. Walnut oil has similar limitations. For cooking, canola oil is a better choice among omega-3-containing oils because it has a higher smoke point, though its ALA content per tablespoon is lower.
Algae Oil: The Direct Source of EPA and DHA
Here’s something most people don’t realize: fish don’t actually produce EPA and DHA themselves. They accumulate it by eating algae (or eating smaller fish that ate algae). Algae-based supplements cut out the middleman, giving you EPA and DHA directly from the original source.
A 14-week clinical trial comparing algal oil to fish oil found that the two were nutritionally equivalent. Plasma levels of both DHA and EPA were non-inferior in the algae group compared to the fish oil group, with the algae group actually trending slightly higher. This means you’re not compromising on absorption or effectiveness by choosing algae over fish.
Algae oil also sidesteps the contamination concerns that come with fish-derived supplements. Because the algae are grown through fermentation in closed, sterile conditions rather than harvested from the ocean, the oil is free of mercury, PCBs, and other marine pollutants. USDA testing of algal oil found heavy metals like mercury, lead, and cadmium all below detectable levels.
Most algae oil supplements provide between 250 and 500 mg of combined DHA and EPA per capsule. Many are heavier on DHA than EPA, which is the reverse of most fish oil capsules. If you want both in significant amounts, check the label and look for brands that list EPA and DHA separately.
Why Your Overall Diet Matters
Your body converts ALA to EPA and DHA using specific enzymes, but those same enzymes also process omega-6 fatty acids. Omega-6 and omega-3 literally compete for the same enzyme binding sites. When your diet is heavy in omega-6 (from vegetable oils like corn, sunflower, and soybean oil, which dominate processed and fried foods), less of your ALA gets converted into the forms you need.
This doesn’t mean omega-6 fats are bad. They’re essential too. But the practical takeaway is that if you’re relying on plant-based ALA as your main omega-3 source, reducing excess omega-6 intake will help your body make better use of it. Cooking with olive oil or canola oil instead of corn or sunflower oil is a simple swap. Cutting back on heavily processed snack foods, which tend to be loaded with omega-6-rich oils, helps as well.
A Practical Strategy
For most people avoiding fish, the most reliable approach combines both plant foods and an algae supplement. The plant foods (flaxseeds, chia seeds, walnuts) provide abundant ALA, which covers your baseline omega-3 needs and contributes some EPA conversion. The algae supplement fills the gap for DHA and EPA that plant foods can’t efficiently provide on their own.
If you’re vegan, pregnant, or don’t eat any seafood at all, an algae-based DHA/EPA supplement is especially worth considering, since DHA is critical for brain and eye development and the conversion from ALA alone may not produce enough. For someone who simply dislikes fish but eats an otherwise varied diet, getting generous amounts of ALA from whole foods and adding an algae capsule a few times a week covers your bases without any compromise compared to a fish-eating diet.