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Are you getting enough omega-3s? These vital fats are beneficial for heart, brain and eye health, but it’s not just the amount that matters. The type of omega-3s in your diet could determine the health benefits you’re getting — especially if you don’t eat fish.

Long-chain omega-3 fatty acids called EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are found in marine sources such as fatty fish and fish oils. Another type of omega-3s is ALA (alpha-linolenic acid), which is found in plant sources such as flax seeds, canola, chia and walnuts.

Most Americans aren’t getting enough EPA and DHA. That’s of concern because there is strong evidence that these omega-3s reduce triglyceride levels to help lower the risk for heart disease or heart attack. There is some evidence that these healthy fats may also reduce blood pressure and improve blood vessel function. And those are just some of the heart-health benefits. The evidence for these benefits in ALA isn’t as strong.

Penny Kris-Etherton, distinguished professor of nutrition at Pennsylvania State University, points out that, “We really haven’t seen evidence for benefits of plant omega-3s on cognition or in preventing stroke.”

Bruce Holub, professor at The University of Guelph adds, “EPA and DHA are shown to be quite effective at lowering triglyceride levels in the blood, while equal amounts of ALA had no effect.”

Getting enough DHA is especially important for pregnant women because it’s essential for healthy development of a baby’s brain and eyes.

ALA is a shorter-chain omega-3 fatty acid that can be converted into EPA and DHA. The problem is the process isn’t very efficient, so meeting your needs for long-chain omega-3s through plant-based sources isn’t possible. That’s why it’s essential to get enough EPA and DHA in your diet.

How much EPA and DHA do you need?

Health organizations recommen d healthy adults get 250 to 500 milligrams of EPA and DHA per day. If you have heart disease, the American Heart Association recommends a daily dose of 1000 mg total of EPA and DHA. For high triglycerides, 2000 to 3000 mg is recommended. Talk to your doctor before taking more than 3000 mg of omega-3s a day.

To meet your EPA and DHA needs, start with food sources before supplements. With foods such as fatty fish, you’re also getting other important nutrients such as high-quality protein and vitamin D. Eating two servings of fatty fish per week gets most people to their daily goal. For example, wild salmon and mackerel have upward of 1,500 mg of omega-3s per 3.5-ounce serving. For people who need higher doses or don’t eat fish, EPA and DHA supplements are recommended.

So why aren’t you eating fish or taking fish oil supplements . . . or getting enough of them? Here are some of the most common reasons I hear in my nutrition practice and what to do about them.

You’re concerned about mercury

Eating enough fish for health benefits while also keeping mercury levels at bay can seem like a challenge. It’s not. Focus on eating lower-mercury fish such as salmon and light canned tuna. If you’re pregnant, the Food and Drug Administration recommends getting up to 12 ounces per week of low-mercury fish and shellfish such as shrimp (which is way below the amount most people are eating).

If you’d rather take supplements, look for fish oil made from smaller fish such as anchovies. They have short life spans so they don’t accumulate as many contaminants as larger fish. You can also visit Consumer Reports to see which brands they’ve found to be the cleanest.

All things considered, the substantial health benefits of eating fish far outweigh any potential risks.

You’re vegetarian or vegan

If you’re following a plant-based diet, you’re not out of luck when it comes to getting long-chain omega-3s. Algae oil supplements are available as a plant-based source of DHA and EPA.

Despite the low conversion rate of plant-based omega-3s to EPA and DHA, the benefits of ALA shouldn’t be ignored. ALA sources such as walnuts, flax seeds and chia seeds also provide heart-healthy fiber along with protein and other nutrients not found in supplements. Further, the literature is still emerging on the benefits of plant-based omega-3s for heart health, brain health and more.

According to Kris-Etherton, there are some prospective long-term studies on ALA linking higher intakes with a lower risk of cardiovascular events and death, just as we’ve seen with EPA and DHA.

So it’s not that the plant-based omega-3s aren’t good for us. It’s that we know more about what the longer-chain omega-3s can do.

You get your omega-3s from eggs or margarine

To produce omega-3 eggs, chickens are fed flax seed so they convert some of the ALA into DHA. Still, you’re not getting enough long-chain omega-3s to get the health benefits or justify the higher cost.

There are also margarines, yogurt, milk and more foods that are fortified with EPA and/or DHA. Clearly some choices are healthier than others: Adding extra margarine to everything to get your omega-3s could mean you’re also loading up on extra calories and fat you don’t need. Fortified foods contain between 30 and 100 mg of EPA and/or DHA. Your daily goal is 250 to 500 mg, so you’ll likely still need to include fish or supplements.

All in all, food-based sources of EPA and DHA should be at the top of your list to meet your needs. Adding in plant-based sources of omega-3s (ALA) certainly can’t hurt and provides other nutritional benefits. Based on what we know to date, plant foods containing ALA shouldn’t be your sole source of omega-3s.

Christy Brissette is a dietitian, president of 80TwentyNutrition.com and a spokeswoman for GOED (Global Organization for EPA and DHA Omega-3s), a nonprofit association that educates people on the health benefits of EPA and DHA. Follow her on Twitter @80twentyrule.