Fish Oil vs. Cod Liver Oil Supplements: Which Is Better for Heart Health?

Reviewed by Dietitian Madeline Peck, RDN, CDN

Key Points

• Fish oil is more widely studied for heart health, and there is more evidence to support its health claims.

• Cod liver has lower omega-3 content than fish oil.

• Always consult a health care provider before starting fish oil or cod liver oil supplements.

From store shelves to wellness routines, fish oil  and cod liver oil have become go-to supplements for people looking to support their heart health. Although similar, fish oil is typically derived from the tissues of a variety of oily fish like mackerel, salmon or tuna, while cod liver oil is extracted from the liver of cod. Since both supplements share an oceanic origin, they're often assumed to offer the exact same heart-health benefits. However, key differences in their nutrient profiles set them apart. We spoke with registered dietitians to break down how these supplements compare and determine which one is the better choice for improving your cardiovascular health.

How Fish Oil Affects Heart Health

Few supplements have attracted more attention for their potential heart-health benefits than fish oil. Much of that interest stems from the two omega-3 fatty acids  it contains: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). According to Lauren Williams, M.C.N., RDN, LD , these omega-3 fatty acids may support heart health by lowering triglycerides, reducing inflammation and keeping blood vessels healthy and flexible.

Triglycerides are a type of fat in the blood that, when elevated, is associated with an increased risk of heart disease. Studies show that EPA and DHA in fish oil may help lower triglycerides  by reducing how much fat the liver produces and releases into the bloodstream. These omega-3s also have anti-inflammatory properties that may help reduce chronic inflammation, a process that can damage the inner lining of blood vessels over time. Together, these effects help support smoother blood flow and decrease the workload on the heart.

While these benefits are promising, Williams highlights that there are nuances to keep in mind when supplementing with fish oil. Prescription-strength fish oil is often preferred to over-the-counter supplements because it provides more reliable dosing and greater assurance of purity. Evidence also suggests that the cardiovascular benefits may be more pronounced in EPA-only fish oil supplements compared to products with combined EPA and DHA formulations. Additionally, high-dose DHA supplementation may raise harmful LDL cholesterol in some individuals and is linked to a higher risk of atrial fibrillation. Therefore, Williams cautions that it is important to always take fish oil under the guidance of a health care provider.

How Cod Liver Oil Affects Heart Health

Similar to fish oil, cod liver oil is a source of omega-3 fatty acids, which play a key role in its cardiovascular effects. Limited research suggests that, when taken alongside cholesterol-lowering medications, it may help lower LDL and total cholesterol levels. The researchers also note that combining cod liver oil with statin therapy  may allow for lower statin doses under medical supervision, potentially helping reduce medication-related side effects. Still, more research is needed to verify this effect.

However, Michelle Routhenstein, M.S., RD, CDCES , points out that cod liver oil supplements typically contain lower amounts of EPA and DHA compared to concentrated fish oil supplements, which means it may take a higher dose to reach the levels used in some studies.

Cod liver oil is a rich source of essential vitamins and minerals. That said, it is worth mentioning that cod liver oil naturally contains high amounts of vitamin A and D . These vitamins are fat-soluble, which means they can increase the risk of toxicity, shares Routhenstein. "If someone is considering taking cod liver oil, they would also need to look at other supplements they're taking and foods they regularly consume to make sure they don't consume more than the daily upper limit of vitamin A or vitamin D (3,000 micrograms per day and 4,000 IU per day, respectively, for those 19 years of age and older)," Williams adds.

Fish Oil vs. Cod Liver Oil: Which Is Better for Heart Health?

Although fish oil and cod liver oil share similarities, one has a clear advantage when it comes to improving your heart health. "For cardiovascular benefits, fish oil would be the better choice, as it is more readily studied for cardiovascular benefits, typically contains higher amounts of EPA and DHA, and doesn't come with the risk of vitamin A or vitamin D toxicity," says Williams.

That said, not all fish oil supplements provide equal benefits. Routhenstein shares that it's important to check the EPA and DHA content on the supplement label , since the amount can vary considerably between products. "You want to choose a dose that aligns with your individual needs, so you don't under- or overconsume these essential fatty acids," she explains. More importantly, you should always speak to a health care professional  before beginning a new supplement to ensure you are taking the right product, dose and formulation for your specific health goals.

Expert Tips for Better Heart Health

While supplements can provide additional support, the lifestyle habits you practice every day play the biggest role in protecting long-term heart health.

• Prioritize a heart-healthy diet. Williams explains that it's best to replace foods rich in saturated fat  with those that contain unsaturated fat, as well as focus on fiber-rich foods like vegetables, fruits, whole grains and beans . In addition, Routhenstein adds that people with heart disease often lack nutrients such as potassium, magnesium, calcium and selenium that your heart needs to thrive. Eating a varied, balanced diet can help you meet your nutrition needs for these essential nutrients.

• Exercise regularly. "For adults, aim for 75 minutes of vigorous-intensity physical activity or 150 minutes of moderate-intensity physical activity [per week], along with a couple of days per week of resistance training. Kids and teens need at least 60 minutes of active play time daily," says Williams.

• Limit added sugar. Excess sugar intake can contribute to cardiovascular disease risk. Minimize added sugar from foods and drinks to no more than 25 to 36 grams per day.

• Get more quality sleep. "Having consistent and healthy sleep routines helps promote a healthy nocturnal dip in blood pressure, which allows the heart and blood vessels to rest and recover, supporting vascular health and reducing cardiovascular risk," says Routhenstein.

Our Expert Take

When comparing fish oil and cod liver oil for heart health, fish oil comes out on top. Not only is it higher in omega-3 fatty acids, but it also has stronger research supporting its cardiovascular benefits. That doesn't mean cod liver oil isn't beneficial, but for those seeking cardiovascular benefits, fish oil is the more practical choice. However, before heading to your nearest supplement shop, you should always talk to a health care professional to ensure fish oil supplements are safe and effective for you. Still, no supplement can outdo the fundamentals of heart health, which include a heart-healthy diet , regular exercise  and good-quality sleep .

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