The benefits of Omega-3 fatty acids are emerging as more and more studies are done. Along with reduced risk of cardiovascular disease, they have been associated with brain development and creating more radiant skin. Yet not all omega-3 fatty acids are the same. Understanding the different types of these long chain fatty acids and what they do can help you decide the best foods to include in your diet.

What Omega-3 Fatty Acids Are

You’ve probably heard of good-for-you monounsaturated fat found in foods such as olive oil. You know that the saturated fat in butter should be used in moderation. Omega-3 fatty acids fall into a third group, polyunsaturated fat, which plays an important role in every cell of the body. There are two categories of omega-3: land plant-based and marine-based. Alpha-linolenic acid (ALA) is land plant-based; docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and docosapenteonoic acid (DPA) are marine-based. While both categories contribute to good health, each originates from different sources and offers different benefits, so it’s wise to eat a mix of both.

What Omega-3 Fatty Acids Do

One of the most studied benefits of omega-3 includes reduced risk for cardiovascular disease. The Institute of Medicine recommends 1.6 and 1.1 grams of ALA per day for men and women, respectively, as recommended adequate intakes. The American Heart Association recommends eating two servings of fish per week (roughly 8 ounces or a total of 250 milligrams of EPA and DHA per day), for primary prevention of coronary heart disease and stroke. Evidence also suggests that even higher doses of marine-based omega-3 may improve blood triglyceride levels and lower blood pressure.

Consuming DHA is especially important for pregnant women as research suggests DHA helps support brain development. This is a bit of a balancing act, since pregnant women are also advised to eat only those fish and seafoods lowest in methyl mercury. The good news is that sardines, which are low in methyl mercury, are chock full of omega-3.

Omega-3 fatty acids may bring even more benefits. Their role in vision (our retinas in particular) and even neurological and mental health are currently being researched.

Marine-Based Omega-3 Essential Fatty Acids

To maximize the benefit of eating seafood, choose the fattier DHA-rich fish that are low in pollutants including: herring, wild Alaskan salmon, barramundi, canned Pacific albacore tuna, farmed rainbow trout, wild oysters, and sardines. These fish feed on microscopic plants in the ocean, which are the original sources of DHA. With advances in technology, DHA can now be extracted from these plants in the form of algal oil. Foods such as milk and orange juice are sometimes fortified with this oil and make for good fish alternatives. (Note, however, that eating fish and seafood instead of DHA supplements means you also get protein, iron, and vitamin B12.)

For more on healthful, sustainable seafood, see the Monterey Bay Aquarium’s Seafood Watch.

Land-based Omega-3 Essential Fatty Acids

ALA is the land plant-based source of omega-3 and can be found in concentrated doses in foods such as flaxseed oil, canola, wheat germ, hempseed, and soybeans, plus walnuts, flaxseed, and soybeans. Nutritious foods made with these ingredients also offer significant sources of ALA, including salad dressing, tofu, granola, some breakfast cereals and energy bars, and eggs from flaxseed-fed hens. To make sure you’re getting the recommended amount of ALA, aim for 1-4 servings of these foods daily. ALA provides an additional source of DHA and EPA in small amounts by the body converting about 10% of ALA into DHA and EPA. However, this amount should not be relied upon as the only source of omega-3.