Is eating fish truly healthy for the heart? Here’s what science says

Fish with more than 5% fat or fatty fish have long been hailed as beneficial against heart diseases. Studies have found such fish lowers risk of heart disease compared with those who don't eat fish.

A closer look by scientists have revealed that the health benefits of consuming fatty fish is mostly owed to high levels of omega-3 fatty acids, according to scientists at Harvard's T H Chan School of Public Health, reports Harvard Health Publishing.

"The science linking fatty fish and heart health continues to evolve, but the evidence still points to omega-3s as a way to further protect against heart attacks and strokes," said Eric Rimm, a professor of epidemiology and nutrition at the T H Chan School of Public Health.

Omega-3s

The Harvard Health Publishing writes that omega-3s are essential fats, meaning the body can't make them and needs to absorb them from food.

There are three main types of omega-3s: eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and alphalinolenic acid (ALA).

EPA and DHA are found in seafood, especially fatty fish like salmon, mackerel, sardines, tuna, pollock, and cod. ALA is found mainly in nuts and seeds like flaxseed, chia seeds, pumpkin seeds, and walnuts, and in plant oils such as flaxseed, soybean, and canola oils.

"Your body can use ALA to make EPA and DHA, but the conversion is modest," said Rimm.

While all three omega-3s benefit the heart, EPA and DHA found in fatty fish have a more direct effect than ALA. Still, experts recommend that both fish and plant omega-3s be part of a healthy diet.

Why are omega-3s so helpful?

They reduce triglycerides (a type of fat in the blood) and increase "good" HDL cholesterol. Omega-3s slow plaque buildup in arteries that can cause blood clots and trigger heart attacks and strokes, according to the Harvard Health Publishing.

They help to ease inflammation and lower blood pressure. It's probably no surprise that fatty fish is a staple in most science-backed heart-healthy eating patterns, such as the Mediterranean and DASH diets.

How much should you eat?

The American Heart Association recommends eating two 3-ounce servings of fatty fish weekly as there doesn't appear to be extra heart benefit from eating more than this.

Besides, some fatty fish have higher amounts of omega-3s than others.

Vegetarians and vegans can get enough omega-3s by increasing their intake of plant-based ALA, said Rimm.

There also are algae-based EPA and DHA supplements available, and initial research shows their levels are comparable to fish oil.

However, relying on supplements probably shouldn't be your preferred strategy. Studies that have looked at omega-3 supplements' effect on heart health have shown mixed results. An analysis published Dec. 21, 2021, in Circulation found that taking omega-3 supplements may even slightly increase the risk of atrial fibrillation.

"Based on the current evidence, there is little reason to take an omega-3 supplement if you already eat fatty fish," said Rimm.

Farmed or wild?

Rimm recommends eating a variety of fatty fish to avoid mercury contamination.

"Overall, the benefits from eating fatty fish outweigh any possible risks from (mercury) contamination."

Research has found that most farmed and wild fish have similar omega-3 amounts, except farmed salmon, which actually has more omega-3s than wild. Canned fish also is on a par with wild fish in terms of omega-3s. 
How fatty fish is prepared usually doesn't matter, as cooking won't substantially change its omega-3 content," said Rimm.