- Prescription fish oil may lower high triglycerides and reduce heart risks in 4 to 12 weeks.
- Over-the-counter fish oil supplements vary in quality and may not offer the same benefits.
- Eating fatty fish twice a week is a proven way to support heart health without supplements.
Fish oil is a well-known source of omega-3 fatty acids, nutrients found in high concentrations in the eyes and brain. Unlike other nutrients, your body can’t make omega-3s on its own, so it’s important to get them through food—like fish—or supplements.
Often, fish oil is touted for its heart-health benefits, but taking a supplement isn’t right for everyone—and improvements aren’t always immediate. We spoke with a cardiologist to break down the science, expectations and timeline for fish oil’s impact on heart health.
How Fish Oil Supports Heart Health—And When Benefits Might Show Up
Fish oil contains two key omega-3 fatty acids: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), in varying amounts, which are often marketed as heart-healthy. You may have seen them marketed as a way to promote heart health. But before reaching for a supplement, consider this: the research is not promising for most people.
“There have been many studies conducted on fish oils over the years. Although some have shown benefit in select populations, when used for prevention in otherwise healthy patients, multiple, well-conducted, very large trials have not shown a benefit,” says Eugenia Gianos, M.D., FACC, chair of the American College of Cardiology’s Prevention of Cardiovascular Disease Council and director of cardiovascular prevention at Northwell Health.
Taking fish oil without a medical reason may even be harmful. Some studies have linked fish oil supplements with an increased risk of atrial fibrillation, a type of irregular heart rhythm, adds Gianos. They should be used in patients where the benefits are likely to be greater,” she says—primarily those with very high triglycerides. Triglycerides are a type of fat in the blood, and elevated levels can increase the risk of plaque buildup in the arteries, potentially leading to a heart attack or stroke.
In addition, it’s also important to consider the type of fish oil that physicians recommend for high triglycerides: prescription fish oil. That’s because over-the-counter supplements are not FDA-approved for managing high triglycerides, and their quality and dosage can vary widely. Many also contain impurities.
Another key difference is dosage. Prescription fish oil delivers a much higher dose of omega-3s than over-the-counter supplements. To reach a similar amount using nonprescription fish oil, you’d need to take multiple capsules, which can increase the likelihood of gastrointestinal side effects, including nausea and the unpleasant “fish burps” many people experience.
Prescription versions, such as icosapent ethyl (Vascepa), deliver a much higher dose of EPA and have been shown to reduce inflammation, stabilize arterial plaque and lower the risk of heart attack and stroke, notes Gianos.
Back to the question at hand, though: When will you notice a benefit? If your healthcare provider recommends taking a prescription fish oil medication to lower your triglycerides, you should see a benefit in about 4 to 12 weeks, adds Gianos.
How to Use Fish Oil Wisely for Heart Health
Although you can easily purchase fish oil supplements at the store or online, first make sure your healthcare provider recommends you take one. For lowering triglycerides, the typical dose is 2 grams twice daily, taken with meals.”Fish oils are generally very safe. They are unlikely to interact with other medications and are well tolerated,” says Gianos.
For most people, though, the best way to get omega-3s for heart-health benefits is through food. Fatty fish such as salmon, sardines, mackerel, anchovies, bluefin tuna, mussels and oysters are all excellent sources. “This has been a guideline recommendation for decades due to research showing benefits for the prevention of heart disease and can be a healthy way to get important protective nutrients,” she explains.
The American Heart Association recommends eating fish twice a week—a target that supports heart health without the need for supplements in most cases.
Our Expert Take
Fish oil supplements are often thought to be great for your heart, but evidence doesn’t support their use for everyone. Plus, in some cases, it can lead to harm or unpleasant side effects. If you’re managing high triglycerides, prescription fish oil may offer measurable benefits within a few weeks. But for most people, eating fish regularly is a stronger, more established strategy for supporting heart health.
