Heart disease remains the leading cause of death for men, women, and people of most racial and ethnic groups in the United States. In the search for better heart health, few supplements have generated as much buzz as fish oil.

The fascination with these fatty acids began in the 1970s when researchers noticed something peculiar about Inuit populations: Despite a diet high in fat, they had remarkably low rates of heart attacks. The secret appeared to be their consumption of cold-water fish rich in Omega-3s.

But does that mean everyone should be taking fish oil supplements? And is fish oil good for you?

Health Matters spoke with Dr. Sean Mendez, a cardiologist at NewYork-Presbyterian Brooklyn Methodist Hospital, to break down exactly what Omega-3 fatty acids do for our bodies and whether you should incorporate them into a heart-healthy diet.

Let’s start with the basics. What are Omega-3 fatty acids?

Dr. Mendez: Omega-3s are a type of polyunsaturated fat. Unlike some other fats, our bodies don’t naturally produce them, so we have to get them from dietary sources.

When we talk about heart health, we are really focusing on three specific types. There is alpha linolenic acid (ALA), which comes from plant sources like walnuts, chia seeds, and flaxseed oil. However, the two “powerhouse” molecules that people usually refer to when discussing fish oil are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These are primarily found in marine sources and seafood. While your body can break down ALA into EPA and DHA, it happens at lower levels, so we mostly focus on marine sources for those direct heart benefits.

How do Omega-3s help the heart?

We know that high levels of saturated fat increase cardiovascular disease, but unsaturated fats like Omega-3s work differently. The strongest evidence we have is that Omega-3s lower triglycerides.

Triglycerides are a type of fat in your blood that, when elevated, can increase your risk of heart disease even if your other cholesterol numbers are controlled. Omega-3s lower these levels in a dose-dependent manner – meaning the higher the dose (and the higher your starting triglycerides), the more they go down.

There are other potential benefits, like:

• Anti-inflammatory effects: They may help reduce inflammation in the body.
• Blood pressure: They can improve endothelial cell function (the cells lining your blood vessels), helping them relax. This can lead to a reduction in blood pressure.
• Plaque stabilization: There is some evidence that Omega-3s might help stabilize plaque in the arteries, making it less likely to rupture and cause a heart attack.

If someone wants to prevent heart disease, should they reach for a supplement or focus on food?

The main focus should definitely be on dietary changes. Most cardiovascular societies and government agencies recommend a healthy diet that includes at least two servings of fish per week.

Specifically, you want to look for oily, cold-water fish that are high in EPA and DHA. Some of the best sources are Atlantic salmon (wild-caught is preferred), mackerel, anchovies and herring, sardines, and oysters.

Even if you can’t afford wild salmon, swapping red meat or fried foods for white fish like tilapia or cod is still a good change, even if those fish have lower oil content. It’s about substituting detrimental foods for healthier options.

What about those who don’t eat fish? Are supplements a good “plan B”?

The data on over-the-counter supplements for general prevention is pretty mixed. One major study, the VITAL trial, showed that taking one gram of fish oil per day didn’t significantly reduce overall major cardiac events, though there were signals that it might reduce heart attacks specifically.

If you are generally healthy, the main focus should be on diet, exercise, and not smoking. However, if you cannot get Omega-3s through your diet, a supplement isn’t unreasonable, but you have to be careful about what you buy.

If someone decides to take a supplement, what should they look for?

Supplements aren’t regulated by the FDA the same way prescription drugs are, so the quality can vary. You’ll want to check the dosage. Many supplements say “1,000 mg of fish oil” on the front, but when you turn the bottle over, they may only contain 400 mg of actual EPA and DHA. And check the ingredients. Some supplements contain fillers or even saturated fats.

You also want to take it with fat. Your body needs enzymes to break down these fatty acids, which are released when you eat fat. If you take the pill on an empty stomach, you won’t absorb it as well. So, take it with a meal.

Are there prescription options? How are they different?

Yes. There are prescription Omega-3s, such as Vascepa, which is pure EPA. These are typically used for patients with very high triglycerides or those who already have heart disease or diabetes and need to reduce residual risk. The doses used in prescriptions (often 4 grams daily) are much higher than what you find in standard supplements.

Are there side effects of fish oil?

The most common complaints are “fishy burps,” nausea, or a fishy taste in their mouth. A good tip is to freeze the pills – this can help reduce the fishy taste. In rare cases, some prescription formulations have been associated with rashes or eczema.

Is there anyone who should not take fish oil supplements?

While generally safe, there are a few groups that need to be cautious. First, those with seafood allergies should speak with their doctor. Because Omega-3s have anti-inflammatory properties, lab studies have shown they can increase bleeding time though this has not been shown to cause increased bleeding risk in clinical studies. However if you’re on a blood thinner, have a high risk for bleeding, or have a known bleeding disorder, talk with your doctor first.

The FDA recommends limiting over-the-counter supplementation to two grams per day. Higher doses – like the four grams used in prescription therapies – should only be taken under a doctor’s supervision.