Omega-3 fats are a type of polyunsaturated fat that your body needs but cannot make on its own

Omega-3 fats are essential fatty acids, meaning your body requires them to function but cannot produce them internally. You have to get them from food or supplements. Three main types exist: ALA (alpha-linolenic acid), found mostly in plant oils; EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), both found primarily in fish and marine sources. Your body can convert small amounts of ALA into EPA and DHA, but the conversion is inefficient—typically less than 10 percent—which is why fish and marine oils are considered more direct sources of the forms your body uses most readily.

Fish and marine oils contain EPA and DHA in ready-to-use form, so your body does not have to convert them. This is why they appear in supplements and why people who eat fish regularly tend to have higher blood levels of these two omega-3 types. The amount varies by fish species and what the fish ate, but fatty fish like salmon, mackerel, and sardines consistently deliver substantial quantities.

Key Takeaways

  • Omega-3 fats EPA and DHA, found in fish and marine oils, support heart rhythm, blood vessel function, and brain cell structure.
  • Your body cannot make omega-3 fats and converts plant-based ALA into EPA and DHA very inefficiently, so marine sources deliver them more directly.
  • Research shows regular omega-3 consumption is linked to lower triglycerides and reduced inflammation markers, though individual results vary.
  • Fish oil supplements contain concentrated EPA and DHA but may cause digestive side effects, and some people need to avoid them due to medications or medical conditions.

How omega-3 fats work in your heart and blood vessels

EPA and DHA influence how your heart beats and how your blood vessels respond to stress. They help regulate heart rhythm by affecting the electrical signals that control each heartbeat. They also reduce triglycerides—a type of fat in your blood—and appear to lower inflammation in blood vessel walls. This combination of effects is why cardiologists often discuss omega-3 intake with patients who have heart disease risk factors or existing heart conditions.

The anti-inflammatory effect extends beyond the heart. Omega-3 fats reduce production of inflammatory molecules throughout your body, which is relevant because chronic inflammation is linked to many age-related conditions. This does not mean omega-3 fats cure inflammation or prevent disease on their own, but they appear to be one factor among many that influence inflammatory markers doctors can measure in blood tests.

Omega-3 fats and brain function

DHA makes up a significant portion of the structural fat in your brain cells, particularly in the outer membrane that allows cells to communicate. Because of this structural role, DHA is especially important during pregnancy and early childhood, when brain development is rapid. Adults also maintain DHA in brain tissue throughout life, and some research suggests adequate omega-3 intake is associated with better cognitive function in older adults, though the evidence is still developing.

The brain's reliance on DHA is one reason why prenatal vitamins often include omega-3 fats and why some infant formulas are now fortified with DHA. If you are pregnant, nursing, or planning pregnancy, discussing omega-3 intake with your healthcare provider can help you understand what level is appropriate for your situation.

What research shows about omega-3 and disease risk

Studies consistently show that people who eat fish regularly have lower average triglyceride levels and lower markers of inflammation compared to people who rarely eat fish. Large population studies also show associations between regular fish consumption and lower rates of heart disease. However, these studies cannot prove that omega-3 fats alone cause the benefit—people who eat fish regularly often have other healthy habits, and fish contains other nutrients beyond omega-3 fats.

Research on omega-3 supplements shows mixed results. Some studies find that fish oil supplements lower triglycerides in people with very high levels, while other studies find minimal benefit in people with normal triglyceride levels. The variation depends on the dose, the duration of the study, and the health status of the people studied. This is why your own doctor's recommendation matters more than general statements about omega-3 benefits—they know your individual risk factors and blood work.

Fish oil supplements versus eating fish

Fish oil supplements concentrate EPA and DHA into capsule or liquid form, so you get a measured dose without eating an entire fish. A typical fish oil capsule contains 300 to 1,000 mg of combined EPA and DHA, whereas a 3-ounce serving of salmon contains roughly 1,500 to 2,000 mg. Supplements are convenient for people who dislike fish or have dietary restrictions, but they cost more per dose than buying fish and do not provide the other nutrients fish contains—protein, selenium, vitamin D, and B vitamins.

Fish oil supplements can cause digestive side effects including fishy aftertaste, nausea, and loose stools, especially at higher doses. Some people find that taking them with food or choosing enteric-coated capsules (designed to dissolve in the intestine rather than the stomach) reduces these effects. If you take blood thinners, have a bleeding disorder, or are scheduled for surgery, you should discuss fish oil supplements with your doctor before starting them, because omega-3 fats can affect blood clotting.

How much omega-3 do you need

There is no official daily requirement for omega-3 fats in the way there is for vitamins, but major health organizations offer guidance. The American Heart Association recommends eating fatty fish at least twice per week, which typically delivers 500 to 1,000 mg of EPA and DHA combined per week. For people with existing heart disease, some organizations suggest higher intakes, sometimes achieved through supplements. For people without heart disease, the evidence supports fish consumption as part of a healthy diet, but does not show that supplements provide additional benefit.

Individual needs vary based on age, health status, medications, and existing conditions. Pregnant people, nursing people, and young children have different considerations than healthy adults. Your doctor or a registered dietitian can review your diet and health history to suggest an omega-3 intake level that makes sense for you specifically.

Plant-based omega-3 sources and their limitations

Plant oils like flaxseed, chia seed, and walnuts contain ALA, the plant form of omega-3 fat. Your body can convert ALA to EPA and DHA, but the conversion rate is low—typically 5 to 10 percent for EPA and even lower for DHA. This means eating a tablespoon of flaxseed oil does not deliver the same amount of EPA and DHA as eating a serving of salmon. For people who do not eat fish or marine products, plant sources are better than nothing, but they are not an equivalent replacement.

Some plant-based supplements now include algae-derived EPA and DHA, which come from the same marine source that fish eat. These supplements offer a way for vegetarians and vegans to get EPA and DHA without consuming fish, though they tend to cost more than fish oil and deliver lower doses per capsule.

Frequently Asked Questions

Can omega-3 fats prevent heart disease?

Omega-3 fats appear to be one factor that supports heart health, but they cannot prevent disease on their own. People who eat fish regularly and have other healthy habits—exercise, not smoking, managing stress—tend to have better heart health outcomes. Omega-3 fats work alongside these other factors, not instead of them.

Is fish oil safe to take every day?

Fish oil is generally safe for most adults at standard doses, but it is not risk-free. High doses can increase bleeding risk, especially if you take blood thinners or have a bleeding disorder. Some people experience digestive upset. Talk with your doctor before starting daily supplements, particularly if you take medications or have existing health conditions.

Do I need a supplement if I eat fish twice a week?

If you eat fatty fish twice weekly, you are likely getting enough EPA and DHA for general health. Supplements are most useful for people who do not eat fish regularly, have specific health conditions, or have been advised by their doctor to take them. Eating fish provides omega-3 fats plus other nutrients supplements do not contain.

Can omega-3 fats help with joint pain or arthritis?

Some research suggests omega-3 fats may reduce inflammation markers in people with rheumatoid arthritis, but the evidence is modest and results vary widely. If you have arthritis, omega-3 fats may be one part of a broader approach to managing inflammation, but they are not a substitute for medical treatment. Discuss omega-3 intake with your rheumatologist.

What is the difference between fish oil and krill oil?

Krill oil comes from small shrimp-like creatures and contains EPA and DHA like fish oil does. Krill oil also contains astaxanthin, an antioxidant. Krill oil costs significantly more per dose and delivers lower amounts of EPA and DHA than fish oil. For most people, fish oil provides the same omega-3 benefit at lower cost, though some people tolerate krill oil better digestively.