Krill Oil 101: Health Benefits, Side Effects, Who Should Take It, and More

If you hear a lot about omega-3 fatty acids, it’s for good reason. These micronutrients are not only critical for some basic bodily functions — and even make up the membranes of our cells — but also plenty of research indicates that they may help lower the risk of many chronic diseases, according to the National Institutes of Health (NIH).

“Omega-3 fats are beneficial for heart, brain, and cell health,” says Vicki Shanta Retelny, RDN, the Chicago-based creator of the podcast Nourishing Notes.

While eating seafood is one of the best ways to get these ever-important omega-3 fatty acids, most Americans don’t eat enough of it, the U.S. Department of Agriculture reports. Fish oil supplements have long been promoted as a way to bridge that nutritional gap in typical Western diets, but they aren’t the only way to get your omega-3s in supplement form. In fact, there are claims that krill oil, which comes from tiny Antarctic crustaceans, may be a better source of the fatty acid. Here, discover all you need to know about krill oil and whether the supplement is right for you.

What Is Krill Oil?

Krill oil supplements are derived from krill, small oceanic crustaceans that resemble miniature prawns, according to researchers at the Australian Antarctic Program. “The word krill actually means ‘small fish’ in Norwegian,” says Amy Kimberlain, RDN, CDCES, a Miami-based Academy of Nutrition and Dietetics media spokesperson. Krill are mostly transparent, except for a slight red coloring on their shells; they often live in large groups of up to 30,000 per square meter, and they are one of the most plentiful animal species on earth, per the Australian Antarctic Program. (However, climate change is rapidly impacting krill’s habitat, research published in 2021 in Frontiers in Marine Science notes.)

Don’t let their tiny size fool you. “Even though they are small, these crustaceans have a ton of DHA and EPA, which are two kinds of omega-3 fatty acids,” Kimberlain adds. DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid) come primarily from aquatic creatures (like fish and crustaceans), and thus are called the “marine omegas,” according to Harvard T.H. Chan School of Public Health.

Krill are a huge part of the diets of whales, penguins, and other ocean dwellers. While they can be consumed by people as well — in Japan, they are prepared in a way similar to shrimp and called okiami, while Norwegians make the creatures into a paste, says Kimberlain — krill are not exactly convenience food. They can be extremely salty and have a hard exoskeleton that has to be removed prior to eating, explains Retelny. Plus, she says, these tiny crustaceans are high in fluorine, a chemical that is toxic at high levels. Fluorine can be removed during the process of making krill oil into supplements.

Krill oil is usually sold as softgels.

Because krill oil is a good source of omega-3 fatty acids, it provides many of the health benefits that come along with it.

Krill Oil May Help Your Heart

There’s a lot to love about krill oil — for your heart’s sake. “Krill oil may be beneficial in lowering our total cholesterol and also triglycerides. Additionally, it may help to increase HDL or ‘good’ cholesterol levels, too,” says Kimberlain. Past research backs this up. In a randomized control study, 1 to 3 grams of krill oil per day helped reduce the study participants’ LDL (“bad”) cholesterol, triglycerides, and blood glucose, while increasing their HDL cholesterol, more so than even fish oil (or, of course, the placebo).

Another study, published in January 2022 in JAMA Network Open found that krill oil helped lower triglyceride levels by 26 percent in people with hypertriglyceridemia, or elevated triglyceride levels, after 12 weeks of supplementation.

Other research, published in 2021 in Mayo Clinic Proceedings found that omega-3 supplements with DHA and EPA can help prevent cardiovascular disease (CVD). “Supplementation with EPA and DHA is an effective lifestyle strategy for CVD prevention, and the protective effect probably increases with dosage,” the researchers note.

Krill Oil Might Reduce Inflammation

Inflammation is not necessarily a bad thing — when you’re ill or hurt, your body starts an immune response, according to the Cleveland Clinic, which helps fight the illness or kick off the wound-healing process. If, however, your body is triggering inflammation and you’re not sick or injured, then you may have chronic inflammation. In that case, krill oil may help lower inflammation levels. A study published in 2016 in Digestive and Liver Disease found that krill oil reduced intestinal inflammation — however, the study was done in a laboratory setting (thus, more research needs to be done).

Krill Oil May Help With Arthritis and Joint Pain

“Along the lines of helping to reduce inflammation, krill oil has been shown to help reduce arthritis pain,” says Kimberlain. Past research, for example, shows that people with arthritis pains who took 300 milligrams of krill oil for 30 days experienced an improvement in pain and stiffness, and some even felt relief after day seven.

A study published in July 2022 in The American Journal of Clinical Nutrition also shows that krill oil improved osteoarthritic knee pain, stiffness, and physical function in adults with mild to moderate knee osteoarthritis. Participants either consumed 4 grams of krill oil a day for six months or a placebo.

A study published in 2016 in PLoS One found that taking 2 grams of krill oil per day helped relieve knee joint pain (in people with mild knee pain), compared with the study participants with mild knee pain who were taking a placebo.

Krill Oil May Help Battle Harmful Free Radicals

Most of us think of fruits and vegetables as antioxidant-containing foods, but seafood, like krill, can have antioxidants, too. Krill oil actually has a pigment called astaxanthin, which is found in a group of antioxidants known as carotenoids. It’s the same antioxidant that gives salmon its pink color, according to the Cleveland Clinic. “This carotenoid has been shown to help fight off the negative effects of free radicals on both our brain and nervous system,” says Kimberlain.

Free radicals are molecules that your body creates when you eat certain foods, or when you’re exposed to harmful substances like cigarette smoke, according to the Mayo Clinic. And these free radicals, they also note, may play a role in cancer and heart disease.

Before you rush out to your local drug store or pharmacy, know this: Krill oil isn’t for everyone. “If you have fish allergies or are on blood thinners, consult with your healthcare provider before taking krill oil supplements,” says Retelny.

Fish oil and krill oil can cause blood thinning for some, which is why it’s important for people who are on blood thinners (or have bleeding disorders or are going to have surgery) to consult with their doctor before taking them, the Cleveland Clinic notes. As for those with a fish allergy, the American College of Allergy, Asthma, and Immunity agrees that you should talk with your doctor before taking any marine supplement.

While doctors might suggest that pregnant women take fish oil (for example, the American Pregnancy Association notes that omega-3s can have a positive impact on pregnancy), you might want to stick to fish oil if you are pregnant or nursing. “As there isn’t much research on the effects of krill oil, it’s cautioned that women that are pregnant or breastfeeding should also not take krill oil,” Kimberlain says.

“Additionally, it may interact with other medications people are taking,” says Kimberlain. In people with diabetes, for instance, some classes of oral medication may not be as effective, so it’s important to discuss your plan with your doctor or dietitian prior to starting, she says.

Also, if you have a sensitive stomach and don’t care for fish, it might not be right for you. “I wouldn’t call this a risk, but many people note that krill oil supplements have a fishy taste,” says Kimberlain. Some other symptoms or side effects may also be possible, such as diarrhea, heartburn, or an upset stomach, she adds.

And a word of caution in general about dietary supplements: The U.S. Food and Drug Administration (FDA) does not approve supplements before they are marketed, and supplement companies don’t have to provide the FDA with information about why their products are safe, the organization notes. Thus, it’s important to take caution when using supplements, and to ask your doctor before you start.

Because of that, Kimberlain suggests that you try to up your seafood game before considering a supplement. “I always suggest a food-first approach,” she says. You can get omega-3 fatty acids by adding cold-water fatty fish, like salmon, trout, herring, mackerel, and sardines, to your weekly menu. If you don’t eat seafood, you can also obtain omega-3s from flaxseed, chia seeds, and walnuts, according to the NIH.

A study published in 2018 in the Journal of Nutritional Science had one group of study participants eat fish, while the other were assigned krill oil capsules. They found that eating fish increased study participants’ vitamin D levels, but those who were in the krill oil group did not see this benefit (however, eating fish and taking a krill supplement both provided their respective groups with beneficial health effects, the researchers note).

If you do decide to take krill oil, follow the dosage instructions on the box or bottle carefully. That’s because taking too much fish oil (or krill oil) can increase your risk of bleeding and potentially impact how your immune system responds, the Mayo Clinic notes.

Perhaps you’ve been a longtime fish oil user, or maybe you’re just now deciding to take a supplement with omega-3 fatty acids. While there are a lot of similarities between the two marine oils, there are a few differences. “Krill oil is on par with fish oil in studies for overall health, as well as cardiovascular health, however it can be more pricey and harder to find,” says Retelny.

Here’s what you need to know when deciding between the two:

Both are taken as a capsule, though the krill oil capsule may be smaller. A study published in Hospital Pharmacy looked at the differences between krill oil and fish oil and noted that krill oil delivers omega-3 oils efficiently in a smaller and more convenient capsule than fish oil.

Krill oil may be more bioavailable. “Research suggests that the EPA and DHA in krill oil may have a higher 72-hour bioavailability than in krill meal or fish oil, however more studies are needed,” says Retelny. (According to the National Cancer Institute, “bioavailability” is the ability of a substance to be absorbed and then put to use by the body.) That study, published in 2015 in Lipids in Health and Disease, notes that a potential reason for this difference could be that the omega-3 fatty acids are “wrapped” in something different (for krill oil it’s primarily molecules called phospholipids, and for fish oil it’s triglycerides), which could affect the bioavailability.

Other reviews of research, like one published in Vascular Health and Risk Management, concluded that while krill oil’s EPA and DHA seem to be more bioavailable, compared with fish oil, more studies need to be conducted before a definitive conclusion can be made.

Krill oil contains additional antioxidants. Just by taking a look at the pills, you’ll see a difference. Fish oil is a golden yellow, and krill oil has a reddish tinge. The red you see is an antioxidant called astaxanthin that may be able to combat free radicals in your body. And fish oil typically does not contain that antioxidant. Past research shows that taking that antioxidant helped lower triglycerides and raise HDL cholesterol in study participants (the study did not look at krill oil specifically). That said, taking a prescription omega-3 fatty acid medication (whether it’s fish oil or krill oil) has been shown to help lower triglyceride levels, the American Heart Association notes.

Krill oil potentially provides more PMS pain relief. Past research looked at whether krill oil or fish oil might help relieve symptoms that can come along with premenstrual syndrome and dysmenorrhea. Researchers found that women taking krill oil used fewer pain relievers after three cycles, compared with women taking fish oil (even though both groups did experience improved symptoms).

There is some debate over whether krill oil is environmentally friendly. While supplement companies will suggest that krill oil is a more sustainable alternative to fish oil, given the vast amounts of krill in the oceans, authorities including Greenpeace say that the issue is not so clear-cut. Krill are an important part of the oceanic ecosystem, and they a food source for many other kinds of wildlife. You can look for products that bear a seal from the Marine Stewardship Council, which is a trustworthy certifier of sustainable supplements.

“If you are looking for a good source of EPA and DHA and can spend a little extra money, look for krill oil,” says Retelny. Still, Kimberlain thinks that krill oil should be a backup plan. “Aiming to include sources from food naturally is always the first approach, and for those that still are unable to obtain an adequate amount, it’s possible then to consider a supplement,” says Kimberlain.

If you have high triglycerides or are at risk of heart disease, you may want to talk with your doctor about krill oil — and whether an omega-3 supplement is right for you.

And as a reminder, before taking any supplement, you’ll want to talk to your doctor, especially if you are allergic to fish, are on blood thinners, or are pregnant or breastfeeding.

If your doctor gives you the go-ahead, follow the dosage instructions on the label, unless your doctor has specific dosage instructions. Research on krill oil has given subjects a wide range of dosages — anywhere from 300 milligrams to 4 grams — thus it’s important to stick with what the manufacturers have intended and deemed safe.

When you walk down the supplement aisle at a health food store, the options can be endless (especially when it comes to omega-3 capsules). You’ll see that krill oil comes in capsule form, and each capsule contains a reddish oil.

If your doctor says it’s fine for you to take krill oil, consider asking them for brand recommendations, the Mayo Clinic suggests, and also whether they have any dosage recommendations. If not, you’ll want to follow the dosage recommendations listed on the bottle, the Mayo Clinic adds. Just know: “There isn’t enough research to determine a set recommended dose for krill oil,” says Kimberlain. The NIH recommends taking no more than 5 grams a day total of EPA and DHA from dietary supplements.

When choosing a bottle, look for brands that have been tested by independent sources, such as NSF International, ConsumerLab.com, or U.S. Pharmacopeia, the Mayo Clinic says. Companies will usually print that info on the box or label, so you should be able to visibly see it. You can also contact the manufacturer if you have questions about the supplement.

If you’re not a big fish fan but want to get beneficial omega-3 fatty acids, specifically EPA and DHA, it’s worth talking to your doctor about whether krill oil is right for you. While it’s often more expensive than fish oil, you may score additional perks — such as free radical–fighting antioxidants, though research is still ongoing.