Fish Oil: Most Common Questions Answered

September 25, 2020 6 min read

Fish Oil is sold almost everywhere now but how healthy is it for you? We went on a hunt and gathered the most common questions related to fish oil and the health benefits it offers.

The Difference Between Fish Oil and Omega 3

Fish oil is a fat or oil that has been extracted from the tissues of a fish.1 Fish oil typically comes from oily fish such as tuna, trout, mackerel and many more.1 Fish oil is rich in omega-3 fatty acids, which provide many benefits for the body. Omega-3 fatty acids are not naturally produced in the body, and therefore, these fatty acids must be obtained from a diet that includes items such as flaxseed oil, fish oil, and fatty fish.2 Consuming fish oil can have many benefits including supporting heart health and fighting inflammation.1 Fish oil supplementation can be beneficial in individuals that do not eat 1-2 portions of oily fish per week.1

The Best Time of Day to Take Fish Oil

Fish oil can be taken at any time of day. Evidence from studies has shown that the potential benefits of fish oil supplements occur with long-term use.3 It is important that regardless of when the fish oil supplement is taken, it is taken with a good source of fat in order to ensure optimal absorption.4

Can Fish Oil Help with Weight Loss?

Fish oil supplements show an improvement in risk factors for heart disease in obese individuals.5 When fish oil supplements are used in combination with an improved diet and exercise, evidence shows that individuals can see weight loss as well.5 Therefore, it is important to avoid relying on fish oil supplements alone for weight loss benefits. Consistent exercise and eating a proper diet along with fish oil supplementation are important ways that can work together to help with weight loss.

Fish Oil and High Cholesterol

Cholesterol is a fat-like substance that is carried throughout the body via proteins called lipoproteins.6 There are two types of lipoproteins involved in movement of cholesterol and they are sometimes referred to as “good” and “bad” cholesterol.6 Low-density protein (LDL) is referred to as the “bad” cholesterol.6

When LDL is high it is associated with higher risk of heart disease and stroke.6 High-density lipoprotein (HDL), conversely, is “good” cholesterol, and higher levels of HDL can lower the risk of heart disease and stroke.6

Evidence has shown that fish oil supplementation can increased HDL.7,8 However, there is not much data to support that fish oil supplementation can cause a decrease in LDL.7,8 Therefore, fish oil supplementation can be beneficial in individuals with high cholesterol, as it will work to increase HDL and reduce the risk of heart disease and stroke.

Fish Oil for Kids

There are some studies that show that fish oil supplementation can be beneficial for children. A systematic review of 16 different studies showed that omega-3 fatty acids helped with improved memory, attention, learning and hyperactivity in children.9 Therefore, it is possible that fish oil supplementation can be helpful in children that have symptoms of ADHD such as those listed above.

There is also some evidence that fish oil supplementation can help reduce symptoms of asthma such as breathing difficulties, coughing and wheezing.9 Lastly, another benefit of fish oil supplementation in children is improved verbal learning ability and memory.9 Evidence shows that after supplementing fish oil in children for 6 months, there was improvement in verbal learning ability and memory.10

Each child may have a different need for omega-3 fatty acids compared to other children his or her age. Therefore, it is important to consult with your child’s pediatrician to assess the risks and benefits of starting fish oil supplementation.  

Can I Give My Dog Fish Oil?

Fish oil is a great supplement to give to your dog because it can help promote a healthy coat, healthy heart, reduce inflammation and reduce itchy and flaky skin.11  The most common side effect of fish oil in dogs is diarrhea, which typically occurs at higher doses of fish oil.11 You can choose between natural fish such as sardines or anchovies, or give them fish oil supplements. Before considering which type of fish oil to give to your dog, it is important to consult with your veterinarian first to individually assess the needs of your dog.

Cod Liver vs. Fish Oil

Cod liver oil and fish oil come from two different sources and both supply omega-3 fatty acids for the body.12 Since humans cannot produce omega-3 fatty acids on their own, it is beneficial to consume either cod liver oil or fish oil. Cod liver oil comes from the liver of codfish, while fish oil can come from a varying source of fish tissue such as salmon, tuna, anchovies, and many more.12 Both of these are considered safe, however it is still important to discuss the benefits of either of these products with you primary care provider.

Side Effects of Fish Oil

Side effects of fish oil supplements are typically very mild. Some of the side effects can include unpleasant taste, unpleasant breath, heartburn, belching, diarrhea and headaches.3 Fish oil supplements can also have some potential drug interactions with medications. Therefore, before starting a fish oil supplement it is important to speak to your doctor. Some doctors may recommend increased intake of natural fish into your diet rather than supplementation.

Is Fish Oil a Blood Thinner

Although fish oil is not categorized as a blood thinner, two FDA approved fish oil products, Lovaza and Vascepa, are associated with prolonged bleeding time.13, 14 Some trials have shown that omega-3 fatty acids have demonstrated increased bleeding time, however, the bleeding time has not exceeded beyond normal limits. 13, 14

Therefore, it is important to be cautious of the potential for bleed risk, however, the bleeding episodes have not been deemed as clinically significant. 13, 14

These have also been studied to have drug-interactions with drugs that affect coagulation, or clotting, of the blood. 13, 14 It is extremely important to discuss benefits and risks of fish oil supplementation with your primary care provider.

Can You Take Too Much Fish Oil?

Although there are no strict recommendations on the amount of fish oil supplementation to consume, dosing will depend on a variety of factors such as age, diseases, and individual health. Studies have looked at as many as 20 grams of fish oil per day, and it is likely that consuming this high of a dose or more than this amount can cause side effects.15 It is important to discuss the appropriate starting dose recommendation with your primary care provider prior to consuming fish oil supplementation. As mentioned above, fish oil can have some unpleasant side effects such as unpleasant breath, belching and stomach upset.3, 15 Therefore, it is important to start at a low dose recommended by your doctor and increase or decrease the dose per your tolerance.



  1. 13 Benefits of Taking Fish Oil. Last Reviewed on December 18, 2018. Accessed on May 1, 2020.
  2. What Are Omega-3 Fatty Acids? Last Reviewed on May 23, 2019. Accessed on May 1, 2020.
  3. Omega-3 Supplements: In Depth. National Center for Complementary and Integrative Health. Last Reviewed on May, 2018, Accessed on May 1, 2020.
  4. Von Schacky C. (2015). Omega-3 fatty acids in cardiovascular disease–an uphill battle. Prostaglandins, leukotrienes, and essential fatty acids92, 41–47. Accessed on May 1, 2020.
  5. Hill, A. M., Buckley, J. D., Murphy, K. J., & Howe, P. R. (2007). Combining fish-oil supplements with regular aerobic exercise improves body composition and cardiovascular disease risk factors. The American journal of clinical nutrition85(5), 1267–1274. Accessed on May 1, 2020.
  6. Centers for Disease Control and Prevention.. Last Reviewed on January 31, 2020. Accessed on May 1, 2020.
  7. Eslick, G. D., Howe, P. R., Smith, C., Priest, R., & Bensoussan, A. (2009). Benefits of fish oil supplementation in hyperlipidemia: a systematic review and meta-analysis. International journal of cardiology136(1), 4–16. Accessed on May 1, 2020.
  8. Petersen, M., Pedersen, H., Major-Pedersen, A., Jensen, T., & Marckmann, P. (2002). Effect of fish oil versus corn oil supplementation on LDL and HDL subclasses in type 2 diabetic patients. Diabetes care25(10), 1704–1708. Accessed on May 1, 2020.
  9. Should Kids Take Omega-3 Supplements? Last Reviewed on October 9, 2019. Accessed on May 1, 2020.
  10. Dalton, A., Wolmarans, P., Witthuhn, R. C., van Stuijvenberg, M. E., Swanevelder, S. A., & Smuts, C. M. (2009). A randomised control trial in schoolchildren showed improvement in cognitive function after consuming a bread spread, containing fish flour from a marine source. Prostaglandins, leukotrienes, and essential fatty acids80(2-3), 143–149. Accessed on May 1, 2020.
  11. Fish Oil For Dogs. American Kennel Club. Last Reviewed on November 29, 2019. Accessed on May 1, 2020.
  12. What Is the Difference Between Cod Liver Oil and Fish Oil? Last Reciewed on March 12, 2018. Accessed on May 1, 2020.
  13. Lovaza package insert. Food and Drug Administration. Last Reviewed on April, 2019. Accessed on May 1, 2020.
  14. Vascepa package insert. Food and Drug Administration. Last Reviewed on February, 2017. Accessed on May 1, 2020.
  15. What Side Effects Can Fish Oil Cause? Medical News Today. Last Reviewed on August 31, 2019. Accessed on May 1, 2020.
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