Fish oil, which is derived from fatty fish like anchovies, mackerel and salmon, is one of the most popular dietary supplements in the world.

Its health benefits primarily come from two types of omega-3 fatty acids — eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Both have been shown to improve heart and brain health, among other benefits.

Recently, a supplement called krill oil has emerged as another product rich in EPA and DHA. Some people even claim that krill oil offers more benefits than fish oil.

This article examines the differences between krill oil and fish oil and evaluates the evidence to determine which is better for your health.

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Most people are familiar with fish oil, but fewer people know about krill oil supplements.

Krill oil is derived from tiny crustaceans called Antarctic krill. These sea creatures are a dietary staple for many animals, including whales, seals, penguins and other birds.

Like fish oil, krill oil is rich in EPA and DHA, the two types of omega-3 fatty acids that provide most of its health benefits. However, the fatty acids in krill oil are structurally different than those in fish oil, and this may impact the way the body uses them (1, 2).

Krill oil also looks different than fish oil. While fish oil is typically a shade of yellow, a naturally occurring antioxidant called astaxanthin gives krill oil a reddish color.

Summary Krill oil is a supplement that contains the omega-3 fatty acids EPA and DHA. The chemical structure of its fatty acids and red color set it apart from fish oil.

While fish oil and krill oil are both excellent sources of EPA and DHA, some studies suggest that the body may absorb and use the fatty acids in krill oil better than those in fish oil.

The fatty acids in fish oil are found in the form of triglycerides. On the other hand, much of the fatty acids in krill oil are found in the form of phospholipids, which many experts believe helps increase their absorption and effectiveness.

One study gave participants either fish or krill oil and measured the levels of fatty acids in their blood over the next several days.

Over 72 hours, blood concentrations of EPA and DHA were higher in those who took krill oil. These results suggest that participants absorbed the krill oil better than the fish oil (3).

Another study gave participants either fish oil or about two thirds the same amount of krill oil. Both treatments increased blood levels of EPA and DHA by the same amount, even though the dose of krill oil was lower (4).

However, several experts have reviewed the literature and concluded that there is not sufficient evidence to prove that krill oil is absorbed or used any better than fish oil (5, 6).

More studies are needed before any definitive conclusions can be made.

Summary Some studies suggest that krill oil may be absorbed better than fish oil. However, further research is needed before any definitive conclusions can be made.

Antioxidants help protect the body from oxidative stress, a type of cell damage caused by molecules called free radicals.

Krill oil contains an antioxidant called astaxanthin, which is not found in most fish oils.

Many people claim that the astaxanthin in krill oil protects it from oxidation and keeps it from going rancid on the shelf. However, no definitive research has confirmed this claim.

However, research has demonstrated that astaxanthin's antioxidant and anti-inflammatory properties may provide some heart health benefits (7).

For example, one study showed that isolated astaxanthin lowered triglycerides and increased “good” HDL cholesterol in people with mildly elevated blood lipids (8).

Nevertheless, this study provided astaxanthin in much larger doses than those you would typically get from krill oil supplements. It is unclear if smaller amounts would provide the same benefits.

Summary Krill oil contains a powerful antioxidant called astaxanthin, which may protect it from oxidation and provide some heart health benefits.

Fish oil is best known for its beneficial effects on heart health, but several studies have demonstrated that krill oil can also improve heart health, possibly to a greater extent.

One study had participants with high blood cholesterol take either fish oil, krill oil or a placebo daily for three months. Doses varied based on body weight (9).

It found that both fish oil and krill oil improved several heart disease risk factors.

However, they also found that krill oil was more effective than fish oil at lowering blood sugar, triglycerides and “bad” LDL cholesterol.

Perhaps even more interestingly, the study found that krill oil was more effective than fish oil, even though it was given at lower doses.

It is worth mentioning that this is only one study. Therefore, more research is needed to compare the effects of krill oil and fish oil on heart health.

Summary One study found that krill oil was more effective than fish oil at lowering several risk factors for heart disease. More research is needed to confirm these findings.

One advantage that fish oil may have over krill oil is that it’s typically much cheaper and more accessible.

While krill oil may share and even exceed many of fish oil’s health benefits, it comes at a higher cost. Because of expensive harvesting and processing methods, krill oil can often be as much as 10 times more expensive than fish oil.

However, fish oil isn’t just cheaper. It is also often much more accessible.

Depending on where you live and shop, you may have a harder time finding krill oil supplements, and you’ll likely find less of a selection than fish oil.

Summary Compared to krill oil, fish oil is typically much cheaper and more accessible.

Overall, both supplements are great sources of omega-3 fatty acids and have quality research to support their health benefits.

Some evidence suggests that krill oil may be more effective than fish oil at improving several risk factors for heart disease. However, this research is very limited, and no additional studies have confirmed that one is superior to the other.

Because of the extreme difference in price and limited research showing one is better than the other, it may be most reasonable to supplement with fish oil.

Although, you may want to consider taking krill oil if you have the extra income to spend and want to follow the limited research that suggests krill oil is better absorbed and may have greater heart health benefits.

It's important to note that fish and krill oil may affect blood clotting, so if you are currently taking blood-thinning medications or have a blood disorder, talk to your health care provider before you take either of these supplements.

Also, make sure you talk to your health care provider if you have any history of fish or shellfish allergies.

Summary Fish oil may be a reasonable choice if you are looking for a quality source of omega-3s at a low price. If you can spend the extra money, you may want to consider krill oil for its potentially greater health benefits, though more research is needed.

While fish oil is derived from fatty fish, krill oil is made from tiny crustaceans called Antarctic krill.

Some studies have shown that krill oil may be better absorbed by the body and more effective at improving risk factors for heart disease. However, more studies are needed to confirm these findings.

If you are looking for a supplement rich in EPA and DHA at a reasonable price, fish oil may be your best option.

On the other hand, if you are willing to spend the extra money for potentially greater health benefits, you may want to consider taking krill oil.

Despite their differences, both krill oil and fish oil are great sources of DHA and EPA and have plenty of research to support their health benefits.