Medically reviewed by Elizabeth Barnes, RDN
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Cod liver oil may help lower cholesterol, improve bone mineral density, and protect eye health.
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Most brands recommend taking around 5 milliliters of cod liver oil each day, but talk to your doctor about how much you should take and for how long.
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Cod liver oil is generally considered safe, but taking too much can lead to unhealthy levels of omega-3s and vitamin A.
Fish oil, including cod liver oil, is one of the most common supplements in the United States—especially among older people who take it in hopes of supporting healthy aging and heart health. But can these supplements actually accomplish what manufacturers promise on the label?
More research needs to be done, but there is some science suggesting that cod liver oil—with its substantial concentrations of vitamin A, vitamin D, and omega-3 fatty acids—could offer benefits.
1. Potential Improvements in Heart Health
The omega-3 fatty acids in cod liver oil may improve heart health by reducing a type of fat called triglycerides. Lower triglyceride levels are associated with better heart health outcomes and a lower risk of stroke, death from cardiovascular disease, and more.
Research also suggests that people who take cod liver oil supplements may have a slightly lower risk of heart attacks, though the evidence isn’t conclusive and more studies are needed.
2. Lower Cholesterol Levels
Having unhealthy levels of fats in your blood—including high cholesterol levels—can be bad for your heart. The omega-3s in cod liver oil may help improve lipid levels in the body, lowering your risk of high cholesterol.
However, the research on cod liver oil’s benefits alone is limited, and benefits may be more pronounced when people take cod liver oil along with another cholesterol-lowering medication.
3. Possibility of Lower Inflammation
Supplements that contain omega-3 fatty acids have been shown to help lower inflammation markers. But cod liver oil in particular may additional benefits—that’s because, in addition to omega-3s, it’s also rich in vitamins A and D, which offer their own anti-inflammatory effects.
Keeping inflammation levels under control may help support normal immune system function, heart health, recovery after exercise, and more.
4. Support for Bone Health
As you age, your risk of osteoporosis increases—this means your bones can become more fragile and prone to fracture. Adding more vitamin D to your diet, along with more calcium, may help reduce your risk.
Cod liver oil is a great source of vitamin D, so it could help support bone health. Older research found that taking a daily cod liver oil supplement could improve bone mineral density, a marker of bone strength. However, this effect was only found in women.
5. Potential Eye Health Benefits
The omega-3s and vitamin A found in cod liver oil may help support your eye health. Vitamin A is important for the production of pigments in your eye’s retina—tissue that processes light into the images you see. And omega-3s have anti-inflammatory properties that may help improve dry eye and a type of vision loss called age-related macular degeneration (AMD).
How Do You Take Cod Liver Oil?
You can cook with cod liver oil, or find products for the skin—such as ointments with antibacterial properties—formulated with cod liver oil.
But most people take cod liver oil as a supplement; you can find it in capsule, liquid, or liquid-filled capsule forms. Most brands recommend about 5 milliliters of cod liver oil daily for adults.
If you’re interested in adding cod liver oil to your diet, make sure you talk to your doctor first to discuss what dosage might be best for you and how long you should take it.
Is Cod Liver Oil Safe?
Cod liver oil supplements are likely to be safe if you take them according to the manufacturer’s dosage recommendations. However, supplements are not regulated by the Food and Drug Administration (FDA) in the same way that medications are, so their safety and quality can vary. Make sure any supplement you purchase is independently tested by a reputable third party organization.
With cod liver oil supplements in particular, there’s concern of potential contamination from heavy metals, which include natural elements like mercury. This is because seafood (and fish products) are more likely to have higher concentrations of these heavy metals.
Though ingesting too many heavy metals can be dangerous, reports and research suggest fish oil supplements generally contain minuscule amounts that shouldn’t be harmful when consumed in moderation.
Potential Drug Interactions
There isn’t much research on the interactions between cod liver oil and other drugs, herbs, or supplements. But that being said, consider talking to your doctor if you currently take any of the following medications:
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Anticoagulants: These medications prevent blood clots. Although rare, supplements high in omega-3 fatty acids may increase your risk of bleeding if you take them with certain medications.
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Drugs that treat calcium loss: Vitamin D helps your body absorb more calcium. So if you’re already taking a drug to help boost your calcium levels, vitamin D-rich supplements (like cod liver oil) could lead to hypercalcemia, or too-high calcium levels.
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Statins: High levels of vitamin D in cod liver oil could interact with certain statins, which are drugs that lower cholesterol.
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Vitamin A: Cod liver oil contains high amounts of vitamin A, so taking it on top of another vitamin A supplement could lead to dangerously high levels.
Taking Too Much Could Lead to Side Effects
There are some potential risks associated with taking too much cod liver oil—or rather, with overdoing it on the vitamins and fats it contains.
Consuming high doses of cod liver oil for a long time could lead to excessive intake of:
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Vitamin A, which can cause headaches, nausea, and blurred vision
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Omega-3 fatty acids, which can cause nausea, heartburn, and diarrhea
For now, more research needs to be done on whether cod liver oil can cause side effects when taken short term at lower dosages.
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