The easiest way to get fish oil naturally is to eat fatty fish two or three times a week. Salmon, sardines, mackerel, herring, and anchovies are the richest sources of EPA and DHA, the two omega-3 fats that give fish oil its health benefits. If you don’t eat fish, plant foods and algae-based options can fill the gap, though with some important trade-offs.
Best Fish for Omega-3s
Not all fish are created equal when it comes to omega-3 content. Cold-water, oily fish pack the most EPA and DHA per serving. Your strongest options include salmon, Atlantic mackerel, sardines, herring, anchovies, and freshwater trout. These all fall into the FDA’s “Best Choice” category for low mercury levels, meaning you can safely eat two to three servings per week (about 8 to 12 ounces total).
Leaner fish like cod, tilapia, and shrimp still provide some omega-3s, but in much smaller amounts. If your goal is to replace a fish oil supplement with real food, stick to the fattier species. A single 3-ounce serving of wild salmon delivers roughly 1,000 to 1,500 milligrams of combined EPA and DHA, which is more than most supplement capsules contain.
Canned options work well too. Canned sardines and canned light tuna (skipjack) are inexpensive, shelf-stable, and low in mercury. They’re a practical way to add fish to your diet without buying fresh fillets every week.
Fish to Limit or Avoid
Some high-omega-3 fish carry enough mercury to outweigh their benefits if eaten regularly. The FDA lists king mackerel, swordfish, shark, marlin, orange roughy, bigeye tuna, and Gulf of Mexico tilefish as choices to avoid due to the highest mercury levels. Albacore tuna, halibut, grouper, and snapper fall into a middle tier: fine occasionally, but limit them to one serving per week.
Plant Sources of Omega-3s
If you don’t eat fish, several plant foods are rich in ALA, a different type of omega-3. Chia seeds lead the pack at about 5 grams of ALA per ounce. English walnuts provide roughly 2.6 grams per ounce, and a single tablespoon of whole flaxseed delivers around 2.4 grams. Hemp seeds and canola oil are other common sources.
Here’s the catch: ALA isn’t the same thing as the EPA and DHA found in fish. Your body can convert ALA into EPA and DHA, but the conversion rate is poor. Estimates range from 5 to 10 percent for EPA and only 2 to 5 percent for DHA, with some research suggesting the conversion to DHA in adults is closer to 1 percent. That means you’d need to eat a very large amount of flaxseed or walnuts to match what a single serving of salmon provides. Plant sources are a valuable part of your diet, but they’re not a direct replacement for fatty fish when it comes to EPA and DHA specifically.
Algae: The Plant-Based Exception
Microalgae are unique among non-fish sources because they produce EPA and DHA directly (fish actually get their omega-3s by eating algae in the first place). Algal oil, extracted from cultivated microalgae, is the only plant-based option that delivers preformed EPA and DHA without relying on your body’s weak conversion process.
A 2025 bioavailability study found that EPA and DHA from microalgal oil supplements were statistically equivalent to fish oil supplements in terms of how well the body absorbs them into the bloodstream. For vegetarians, vegans, or anyone who simply doesn’t like fish, algae-based foods and oils are the most effective natural alternative.
Whole Fish vs. Isolated Oil
Eating whole fish gives you more than just omega-3s. You also get protein, selenium, vitamin D, and other nutrients that work together. Research on how the body processes omega-3s from different sources shows that the fats in whole fish are digested just as efficiently as isolated oils: fish proteins and other components don’t interfere with fat absorption.
One advantage of getting omega-3s from actual fish rather than concentrated supplements is the chemical form. The fats in fish are naturally bound in a form called triacylglycerol, which the body absorbs more readily than the ethyl ester form found in many processed fish oil supplements. This means a piece of salmon may deliver its omega-3s more efficiently than a cheap capsule, even at the same dose on paper.
How You Cook Matters
Cooking method has a real impact on how much omega-3 survives on your plate. Frying is the worst option. Research published in Food Chemistry found that frying causes the greatest reduction in EPA and DHA content, especially when using vegetable oils like corn, soybean, or canola oil. The high heat breaks down omega-3s, and the cooking oil dilutes whatever remains with less beneficial fats.
Boiling and smoking also reduce omega-3 levels, particularly in shellfish. Your best bets for preserving omega-3 content are baking, steaming, and poaching. These gentler methods keep temperatures lower and avoid introducing competing oils. Interestingly, some studies found that certain preparations like curries or gravies can actually concentrate EPA and DHA as fish tissue releases moisture during cooking, sometimes resulting in higher omega-3 levels than the raw fish.
Building a Practical Routine
The Dietary Guidelines for Americans recommend at least 8 ounces of seafood per week, which works out to about two servings. For pregnant or breastfeeding women, the target is 8 to 12 ounces weekly from low-mercury options. Children need less, scaling from about 1 ounce per serving at age one up to 4 ounces by age eleven.
A realistic weekly plan might look like baked salmon one night and sardines on toast for lunch another day. On days you’re not eating fish, add a tablespoon of ground flaxseed to a smoothie or snack on a handful of walnuts. If you’re vegetarian, an algal oil added to salad dressings or taken as a liquid supplement fills the EPA and DHA gap without fish.
The key insight is that your body handles EPA and DHA from food at least as well as from capsules, and in some cases better. Prioritizing two to three servings of fatty fish per week, prepared with gentle cooking methods, is the most straightforward way to get what fish oil supplements promise, without the supplement.