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Published on April 26, 2021

Krill Oil vs Fish Oil: Which Should You Take?

Krill Oil vs Fish Oil: Which Should You Take?

Omega 3 fats are essential in our diet, and there are lots of different sources, such as oily fish, nuts, seeds, and also supplements. There are pros and cons of both food sources and also supplements. So, in this article, I will guide you through the advantages and disadvantages of Krill oil vs fish oil supplements. I’ll also cover who needs to take these supplements, and if krill oil is better than fish oil, and cod liver oil.

What Are Omega Fatty Acids?

There are two types of fats or fatty acids that are essential and can’t be produced in our bodies. These are omega 3 and omega 6. Omega 3 can be broken down into three main forms: alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).

Where Are Omega Fatty Acids Found?

ALA is found in plant oils, such as flaxseed, soybean, and canola oils. DHA and EPA are found in oily fish, fish oils, and krill oils. DHA and EPA are actually synthesized by microalgae—not by the fish—but accumulate in the tissue when they are eaten by fish and shellfish further up the food chain.

Why Are Omega Fatty Acids So Important?

Omega-3 and -6 fatty acids have an important structural role needed for cell membranes. They are also energy sources and are used to form signaling molecules called eicosanoids, comprised of prostaglandins, thromboxanes, and leukotrienes.

There are many different prostaglandins with wide-ranging roles, such as the sensation of pain, inflammation, regulation of pregnancy and birth, control of blood pressure, secretion of stomach acid, contraction, and relaxation of smooth muscle.

Thromboxanes regulate blood clotting by causing constriction of blood vessels and the aggregation of platelets (so they stick together), which are early steps in blood clotting.

Leukotrienes are involved in immune function by attracting immune cells such as neutrophils to sites of inflammation. They also constrict bronchioles in the lungs and make capillary walls permeable.

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This is thought to be because the metabolic products of omega-3 fatty acids are less inflammatory than those produced from omega 6 fatty acids. Western diets are associated with an imbalance of omega-3, -6 such that instead of levels of omega 3 being higher than 6, the reverse is more commonly seen. This is associated with an increased risk of chronic inflammation.[1]

A large systemic review that combined 86 trials involving over 162,000 people looked at the effect of higher omega-3 intake versus lower omega-3 intake for at least a year. This was provided mostly by omega-3 supplements while a few trials gave oily fish. Omega-3 fatty acids have been shown to reduce blood pressure and can be incorporated into your diet by eating oily fish or seeds, such as chia seeds, flax seeds, and nuts.[2]

There are three types of omega-3: those found in oily fish called EPA and DHA and the plant-based ALA.

What Is Krill Oil?

Krill oil is extracted from the bodies of Antarctic krill, a tiny shrimp-like shellfish. Krill oil, fish oil, and cod liver oil are similar in that they all contain DHA and EPA.

Fish oil is extracted from the body of the fish and contains some vitamin A and vitamin D as well. Cod liver oil is extracted from the liver of the fish and contains higher levels of vitamin A and D.

High doses of vitamin A can be toxic as it is a fat-soluble vitamin that is stored by your body. This is why omega 3 supplements that contain vitamin A are to be avoided in pregnancy because high levels of this vitamin may damage the fetus.

Krill Oil Vs Fish Oil

Evidence surrounding krill oil is limited compared with fish oils and cod liver oils. A large portion of the EPA and DHA in krill comes in phospholipid form (whereas fish oil fatty acids are contained in triacylglycerols), which some claim has a higher rate of absorption in the body than fish oil.

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Previously, it was thought that Krill oil was more bioavailable than fish oil, but there were problems with this research with regards to dosing.[3] More recently, a randomized controlled trial in 66 people was performed to answer this question and compared the bioavailability of krill oil compared with fish oil. It found that there was no difference between blood measurements of DHA and EPA. Therefore, the evidence does not support krill oil being “better” or needing lower doses than fish oil.[4]

Krill Oil Vs Fish Oil in Terms of Cholesterol

A study in animals looked at gene expression after supplementation with either krill oil or fish oil. They found that fish oil upregulated (increased gene expression) the cholesterol synthesis pathway more than krill oil. Krill oil was found to upregulate (increase gene expression) more metabolic pathways than fish oil. This suggests that there might be different biological effects between krill and fish oil but more research is needed.[5]

In group (meta) analysis of seven trials totaling 662 participants, Krill oil supplementation was found to reduce low-density lipoprotein cholesterol and triglycerides but not total cholesterol.[6] Whether this translates to decreased risk of cardiovascular disease needs further research.

However, when directly compared, krill oil was not superior to fish oil supplementation and had very similar effects on cholesterol.[7]

Krill Oil Vs Cod Liver Oil

Cod liver oil contains higher levels of vitamin D and vitamin A, which may be toxic in excess. If you want to take a high dose of omega-3, this means you will also end up having higher doses of vitamin A and D. Both of these are fat-soluble vitamins that are stored by the body and can become toxic. Vitamin A supplementation should be avoided during pregnancy due to risks for the baby.

There is a risk that since the liver is used to filter out toxins, there is the possibility that cod liver oil contains more environmental contaminants than fish oil or krill oil.

Are There Risks With Krill Oil?

Less research has been performed on krill oil and although no side effects have been reported, the safe maximum dose of natural astaxanthin has not been determined.

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Krill make up a vital part of the Antarctic food chain and a huge number of species higher up the food chain depend on them. Fishing krill has the potential to catastrophically destabilize this important food chain. Therefore, fish oils are more sustainable than krill oil.

Why Is Krill Oil Red?

The deep red color of krill oil is due to a compound called astaxanthin found in krill. Astaxanthin is also found in other more sustainable sources such as red trout, crab, lobster, and wild salmon. Astaxanthin is a carotenoid antioxidant compound that mops up harmful free radicals.

When to Take Omega-3 Supplement

A large review of 86 trials combined—totaling over 162,000 people—looked to see what the effect of increased omega-3 had on cardiovascular risk. Increasing ALA made no significant difference to blood clots of the coronary arteries supplying the heart (coronary events) but slightly reduced cardiovascular events (diseases related to blood vessels such as clots and rhythm problems) while EPA and DHA reduced serum triglycerides and also reduced the risk of coronary heart disease, such as heart attacks.[8]

They found that EPA and DHA decreased triglycerides (a type of fat) by about 15% and reduced the risk of coronary artery death and coronary events, which are illnesses of arteries supplying the heart. However, they did not affect cardiovascular events (e.g., strokes, heart irregularities).[9]

While increasing ALA made no significant difference to coronary events, it slightly reduced cardiovascular events. This means that the three combined (ALA, EPA, and DHA combined) may reduce the risk of coronary, cardiovascular disease, and lower triglyceride levels, but the effects are small.

One of the ways of decreasing your risk of cardiovascular disease is by lowering your cholesterol—reducing saturated fats in your diet and eating ALA omega-3 (e.g., from walnuts). A grouped meta-analysis has not found any link between omega-3 and dementia, but more information is needed to see if omega-3 can prevent cognitive decline.[10]

Overall, if you aren’t pregnant or intending to get pregnant, then omega 3 supplements are probably unlikely to do you harm and might benefit your long-term cardiovascular risk. It isn’t possible to tell the difference in general between eating enough omega-3 in your diet versus supplementing, but whole foods have other benefits as well.

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Omega-3 supplements often have high levels of vitamin A, which can be harmful in pregnancy. Therefore, you should avoid supplementing or choose a pregnancy-safe version.

If you are vegan, you may consider taking an omega-3 supplement made from algae or seaweed, but these are unregulated and can contain significant quantities of iodine, which can be harmful. Therefore, it is better, where possible, to optimize your diet. There are concerns that part of the benefit of omega-3 is from a whole food effect that isn’t seen with taking a supplement instead.

Tips on How to Get Enough Omega-3 in Your Diet

  • Aim to have oily fish twice a week if you aren’t pregnant or once a week if you are, as the benefit of omega-3 has to be offset by the risk of contamination with heavy metals.
  • Algae and seaweed are the only plant-based sources of EPA and DHA, but ALA can be converted in your body into EPA and DHA.
  • Vegan sources of omega-3 are chia seeds, linseed, hemp seeds, walnuts, and vegetable oils, such as rapeseed. To meet the current guidance for omega-3, you would need to eat about a tablespoon of chia or ground linseeds, or two tablespoons of hemp seeds, or six walnut halves a day.
  • Algae oil is an alternative to fish oil, which makes it an attractive option for vegetarians. But while algae oils do contain large amounts of DHA, most don’t contain any EPA fatty acids at all.

In Summary

Krill oil supplements appear to be safe and as effective as fish oil. They also have the bonus of containing the antioxidant astaxanthin.

However, harvesting krill is not sustainable, and there are risks regarding destabilizing the Antarctic food chain. Instead, aim to include foods rich in omega-3 in your diet to benefit from the “whole food effect,” and eat foods that are naturally rich in carotenoids, such as vegetables, crab, and lobster. Avoid taking high doses of cod liver oil, and avoid it completely during pregnancy due to the risk of vitamin A.

Featured photo credit: Anshu A via unsplash.com

Reference

More by this author

Dr. Harriet Holme

Registered Nutritionist, and doctor

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Published on June 17, 2021

Flaxseed Oil vs Fish Oil: Which Is Better?

Flaxseed Oil vs Fish Oil: Which Is Better?

Both flaxseed oil and fish oil supplements are sources of Omega-3 fatty acids. Omega-3 fatty acids have so many known benefits, such as having a reduced risk of cardiovascular disease, diabetes, certain types of cancer, glaucoma, and stroke. This nutrient is essential for the body’s function, but our bodies are unable to produce them on their own. That’s why you should get enough Omega-3 fatty acids from outside sources as well.

In this article, I’ll discuss flaxseed oil vs fish oil and their various benefits and drawbacks to help you quickly make a more informed decision about which one of these is right for you.

Are These Supplements Safe?

According to the National Institutes of Health, side effects experienced by users of fish oil supplements, if any, are usually mild. These side effects may include unpleasant taste, bad breath, headache, and gastrointestinal symptoms. This could include symptoms such as nausea, diarrhea, or heartburn.[1]

In terms of possible medication interactions, it’s noted that fish oil supplements may interfere with medicines that many Americans take to prevent blood clotting. If you’re on one of these medications or if you have a seafood allergy, it’s important to speak with your doctor before deciding to start taking Omega-3 supplements.

Regarding the safety of flaxseed oil supplements, according to Mayo Clinic, these supplements are also generally considered to be safe. However, they report that if taken in excess and without sufficient intakes of water, users may experience various gastrointestinal symptoms. These symptoms include bloating, gas, and diarrhea.[2]

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The National Institutes of Health (NIH) also advise that these supplements should not be taken during pregnancy. This is because some studies suggest that taking flaxseed oil later in pregnancy may increase the risk of premature birth.[3]

Mayo Clinic notes that, like fish oil supplements, flaxseed oil may also have negative interactions with some medications. Specifically, it’s important to consult your doctor before starting these medications if you’re on medications to reduce blood clotting, lower blood pressure, or manage your diabetes as these may interact negatively with a flaxseed oil supplement.[4]

How Much Should You Take?

The tricky thing about these supplements is that there is no standard recommended dosage for any of them. To be safe, it is recommended that you read the label on the supplement you choose to buy and make sure to only take the recommended dosage.

Regardless of whether you’re taking a fish oil or flaxseed oil supplement, you may benefit from speaking with your primary care doctor to determine what dosage is right for you. They may be able to work with you to come up with an appropriate dosage, which may help prevent unwanted side effects.

If you are interested in researching a particular brand of Omega-3 supplement, you can use the Dietary Supplement Label Database from the National Institutes of Health.[5]

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Flaxseed Oil vs. Fish Oil

Before we get into the various benefits of Fish Oil and Flaxseed Oil supplements, it’s important to have some basic knowledge about Omega-3 fatty acids.

There are three types of Omega-3 fatty acids: Eicosapentaenoic acid (EPA), Docosahexaenoic acid (DHA), and Alpha-linolenic acid (ALA). EPA and DHA come mainly from fish while ALA comes mainly from plant sources such as flaxseed and walnuts.[6] This means that if you choose to take a fish oil supplement, you’ll be getting DHA and EPA, and if you choose a flaxseed oil supplement, you’ll be taking ALA.

Fish Oil Benefits

Fish Oil supplements typically contain oil that has been extracted from fatty fish, such as herring, tuna, or anchovies.[7] The Omega-3 found in fish oil is very important for our heart health. It can reduce the risk of cardiovascular disease and blood clots.[8] It can also help to reduce high blood pressure, which is common among adults in the United States.[9]

They can also help to reduce high cholesterol and plaque formation in your arteries.[10][11] They can also help reduce the risk of sudden cardiac death, which occurs when the heart is either pumping irregularly or ineffectively, making it unable to pump blood as intended to the rest of your vital organs.[12]

These supplements may have non-cardiac benefits as well. Studies show that they can reduce your risk of glaucoma, certain cancers, and certain mental health disorders.[13][14][15]

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Some studies have also shown that including Omega-3 fatty acids from fish oil in your lifestyle may lead to improved weight loss when combined with a healthful diet.[16]

Flaxseed Oil Benefits

As we’ve noted, flaxseed oil contains the third type of Omega-3 fatty acid, Alpha-linolenic acid (ALA). What the body does with ALA is incredibly interesting. It actually converts it into DHA and EPA, which are the Omega-3 fatty acids found in fish oil.

Something important to note, however, is that the body is not all that efficient at converting ALA to DHA and EPA. This means that the benefits of ALA may not necessarily be the same as those that you would get from just taking DHA and EPA. Studies seem to be overall mixed on whether taking flaxseed oil provides the same cardiac benefits as fish oil does. Specifically, it’s unclear whether or not flaxseed oil supplementation can lower cholesterol or reduce your risk of heart disease.[17]

According to the National Institutes of Health, studies have shown that taking flaxseed may help individuals with type 2 diabetes to manage their blood sugar levels. However, it’s important to note that these findings are for flaxseed, no flaxseed oil. NIH does note that it is unclear whether flaxseed oil would provide such a benefit.[18]

One big health benefit of flaxseed oil is its possible cancer-fighting ability. Studies have shown that taking flaxseed oil can stop the growth of cancer cells as well as cause apoptosis or death of cancer cells in certain types of cancer. One study found that the types of cancer which saw benefits from flaxseed oil intakes included breast cancer, cervical cancer, leukemia, and melanoma.[19]

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Flaxseed Oil Vs Fish Oil: Which Should You Take?

When deciding whether to take flaxseed oil vs fish oil supplements, there are some important things to consider. As I’ve discussed, fish oil supplements are a great source of DHA and EPA. In contrast, flaxseed oil supplements provide ALA, which the body ends up converting back to DHA and EPA, although inefficiently.

Additionally, the benefits of fish oil seem to be more deeply studied and more overall conclusive than the benefits of flaxseed oil. Fish oil supplements have been shown to provide so many benefits, including reduced risk of cardiovascular disease, glaucoma, certain cancers, and various mental health disorders.

In contrast, the research regarding the benefits of flaxseed oil supplementation is lacking. While these supplements may have anti-cancer properties, the findings on further benefits are overall mixed.

In terms of safety, these two supplements come out relatively even. They’re both regarded as generally safe. However, both have interactions with various medications that need to be taken into consideration before starting supplementation.

If you’re trying to settle on an Omega-3 supplement, I recommend trying a fish oil supplement over a flaxseed oil supplement. Fish oil has so many proven benefits while the research on flaxseed oil is significantly less convincing. Fish oil also has the benefit of providing EPA and DHA directly, so your body does not need to do any extra work to convert it.

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If you choose to take a fish oil supplement, know that you’ll be quickly reducing your risk of various chronic diseases with overall very minimal effort on your part. As always, make sure to check with your doctor before starting any supplementation to prevent negative side effects or drug interactions.

Featured photo credit: New Food Magazine via newfoodmagazine.com

Reference

[1] National Center for Complementary and Integrative Health: Omega-3 Supplements: In-Depth
[2] Mayo Clinic: Flaxseed and flaxseed oil
[3] National Center for Complementary and Integrative Health: Flaxseed and Flaxseed Oil
[4] Mayo Clinic: Flaxseed and flaxseed oil
[5] National Institutes of Health: Dietary Supplement Label Database (DSLD)
[6] Harvard School of Public Health: Omega-3 Fatty Acids: An Essential Contribution
[7] Healthline: What’s the Difference Between Cod Liver Oil and Fish Oil?
[8] Cleveland Clinic: Omega-3 Fatty Acids
[9] PubMed.gov: Moderate consumption of fatty fish reduces diastolic blood pressure in overweight and obese European young adults during energy restriction
[10] ResearchGate: Omega-3 fatty acids in health and disease and growth and development
[11] PubMed.gov: Effect of omega-3 fatty acids supplementation on endothelial function: a meta-analysis of randomized controlled trials
[12] Mayo Clinic: Ventricular fibrillation
[13] TVST: Oral Omega-3 Supplementation Lowers Intraocular Pressure in Normotensive Adults
[14] PubMed.gov: Dietary fatty acids and colorectal cancer: a case-control study
[15] PubMed.gov: Long-chain omega-3 fatty acids for indicated prevention of psychotic disorders: a randomized, placebo-controlled trial
[16] PubMed.gov: Randomized trial of weight-loss-diets for young adults varying in fish and fish oil content
[17] Mount Sinai: Flaxseed oil
[18] NIH: Flaxseed and Flaxseed Oil
[19] NCBI: Treatment with flaxseed oil induces apoptosis in cultured malignant cells

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