Fish Oil: Why do doctors love prescribing these to heart patients?

fish oil healthy

Last Updated December 20th, 2021

How is fish oil obtained?

Fish oil is obtained from the tissues of oily fish.  Fish oils contain the omega 3 fatty acids called eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).  These compounds are known to reduce inflammation in the body and also provide other health benefits, for example, treating hypertriglyceridemia.  

Fish oil and omega-3 fatty acids have been known to help in a wide variety of health conditions, such as clinical depression, anxiety, cancer, and macular degeneration.  Advantages of fish oil can be inherited from eating fish or even by taking fish oil supplements. Fatty predatory fish like sharks, swordfish, tilefish, and albacore tuna are known to be high in omega-3 fatty acids.  

Fish oil contains omega-3 fatty acids, which have an anti-inflammatory action. Since a cervical cyst formation is an example of an inflammatory response, taking fish oil supplements daily can reduce the risk of inflammation. In other words, fish oil supplements could prevent the formation of nabothian cysts itself. Fish oil supplements are also given to breastfeeding and pregnant women as it helps to improve the vision and overall health of the baby.

Marine and freshwater fish are rich sources of fish oil but vary in contents of arachidonic acid, EPA, and DHA.  The numerous species range from lean fish to fatty fish and their oil content in the tissues have been shown to vary from 0.7 percent to 15.5 percent and also differ in their effects on organ lipids.  

The nutritional content of fish oil

Cold-water oily fish namely salmon, herring, mackerel, anchovies, and sardines are rich in EPA and DHA.  Fish oils from these fish have a profile of around seven times as much omega-3 oils as compared to omega-6 oils.

Amount of Omega-3 fatty acids per 3 oz (85g) serving of popular fish.

  • Herring, sardines:  1.3 to 2.
  • Tilefish:  0.9.
  • Tuna (canned, light):  0.17 to 0.24.
  • Halibut:  0.60 to 1.12.
  • Swordfish:  0.97.
  • Catfish:  0.22 to 0.3.
  • Flounder:  0.48.
  • Shark:  0.83.
  • King mackerel:  0.36.
  • Snapper:  0.22.
  • Barramundi, saltwater:  0.100.
  • Blue eye cod:  0.31.
  • Sydney rock oyster:  0.30.
  • Spanish mackerel, Atlantic, Pacific:  1.1 to 1.7.
  • Salmon:  1.1 to 1.9.
  • Tuna:  0.21 to 1.1.
  • Greenshell/lipped mussels:  0.95.
  • Pollock:  0.45.
  • Cod:  0.15 to 0.24.
  • Grouper:  0.23.
  • Mahi Mahi:  0.13.
  • Orange roughy:  0.028.
  • Red snapper:  0.29.

What are omega-3 fatty acids?

Omega-3 fatty acids are the compounds that are present in plants and marine life.Two types of omega-3 fatty acids are abundant in oily fish:

Eicosapentaenoic acid (EPA):  Eicosapentaenoic acid (EPA) helps the body synthesize chemicals, which are involved in blood clotting and inflammation namely the prostaglandin-3, thromboxane-2, and leukotriene-5.  Fish obtain EPA from the algae that they get through diet.

Docosahexaenoic acid (DHA):  In humans, this omega 3 fatty acid is an important part of the sperm, the retina, the eye, the cerebral cortex, and also an important part of the brain.  Docosahexaenoic acid (DHA) is present throughout the body, but are abundant in the brain, the eyes, the heart, and the breast milk.

Why should you consume fish oil?

People use fish oil for many health conditions namely to lower blood pressure, to lower triglycerides and to lower cholesterol levels.  Fish oil has also been used to prevent diseases such as heart disease, stroke, chest pain, irregular heartbeat, clogged arteries, bypass surgery, heart failure, and rapid heartbeat.  

Fish oil can also prevent blood clots and high blood pressure after a heart transplant. It is used to treat many kidney-related complications namely kidney disease, kidney failure, and kidney complications related to diabetes, cirrhosis, heart transplantation, and Berger disease which is also called as IgA nephropathy.  

Fish oil is widely used to treat dry eyes, cataracts, glaucoma, and macular degeneration. Fish oil is supplemented orally for stomach ulcers caused by Helicobacter pylori (H. pylori), inherited disorder called phenylketonuria, inflammatory bowel disease, pancreatitis, allergy to salicylate, Crohn disease, Behcet syndrome, and Raynaud syndrome.  Women should consume fish oil to prevent painful periods, breast pain, and complications associated with pregnancy such as miscarriage. 

It can help bring down the symptoms of:

High triglycerides

Consuming fish oil from supplements and food sources can reduce triglyceride levels.  The effects of fish oil tend to be the greatest in people who have very high triglyceride levels.  Higher fish oil consumption is related to the reduction of triglyceride levels in higher levels. Fish oil supplements such as Lovaza, Omtryg, and Epanova have been approved by the FDA to lower triglycerides.

Re-blockage of blood vessels

Studies have shown that fish oil decreases the rate of blood vessel re-blockage by up to 45% when given for at least 3 weeks.

Miscarriage Risk

Taking fish oil by mouth helps to prevent miscarriages and increase live birth rates in pregnant women, who suffer from the antiphospholipid syndrome.

Attention deficit hyperactivity disorder (ADHD)

Fish oil has the capability to increase attention, mental function, and behavior in children in the age group of 8 to 13 years who are suffering from attention deficit-hyperactivity disorder (ADHD).  Studies have shown that taking supplements having the combination of fish oil and evening primrose oil improves mental function and behavior in children who are in the age group between 7 to 12 years and who are suffering from attention deficit-hyperactivity disorder (ADHD).  

A combination of fish oil (80%) and evening primrose oil (20%) seems to improve reading, spelling, and behavior when given to children aged 5 years to 12 years with developmental coordination disorder.

Bipolar disorder

Fish oil is also beneficial in treating bipolar disorder.  Taking fish oil along with regular treatments for bipolar disorder seems to improve symptoms of depression in people with bipolar disorder.

Chemo-related weight loss

Consuming a high dose of fish oil can slow weight loss in cancer patients.  Researchers believe that fish oil slows cancer-related weight loss by fighting depression and improving the mood of people with cancer.

Heart disease

fish oil healthyEating fish is known to be effective in reducing the risk of heart disease and keeping the heart healthy.  People who already have heart disease also benefit from eating fish as it reduces the risk factors associated with heart disease.  Consuming fish oil along with the regular medications for heart ailments improves the chances for curing the disease.

High blood pressure

Cyclosporine is a medication, which is used to reduce the chance of organ rejection after an organ transplant, but Cyclosporine is also known to cause high blood pressure.  Consuming fish oil seems to prevent high blood pressure caused by this drug.

Damage to the kidneys

Cyclosporine is a medication, which is used to reduce the chance of organ rejection after an organ transplant but Cyclosporine is also known to cause high blood pressure and cause damage to the kidney.  Adding fish oil to the diet seems to prevent kidney damage in people taking this drug.

Menstrual pain (dysmenorrhea)

Dysmenorrhea is also known as painful periods or menstrual cramps, which is the pain during menstruation.  The onset of dysmenorrhea occurs around the time when the menstruation begins.  Research shows that taking fish oil can improve painful periods and reduce the need for pain medications in women suffering from menstrual pain.

Movement disorder in children (dyspraxia)

Consuming fish oil with the combination of evening primrose oil, thyme oil, and vitamin E is helpful to decrease movement disorders in children with dyspraxia.

Endometrial cancer

Endometrial cancer is a cancer of the endometrium and initially begins in the uterus.  Endometrial cancer is known to first affect the layer of cells that form the lining of the uterus.  Studies have shown that women who regularly eat about two servings of fatty fish weekly have a reduced risk of developing endometrial cancer.

 IgA nephropathy

IgA nephropathy is also known as Berger disease, which is a kidney disease that occurs when IgA deposits build up in the kidneys, causing inflammation that damages kidney tissues.  Research has shown that long-term use of fish oil can slow the loss of kidney function in high-risk patients with IgA nephropathy.  Fish oil gives much higher effects when consumed in higher doses. Also, it is most effective in people with IgA nephropathy who have higher levels of protein in the urine.


Osteoporosis is a medical condition when the bones become fragile and brittle due to bone tissue loss and low bone mass.  Studies have shown that taking fish oil alone or together with calcium and evening primrose oil slows the rate of bone loss and increases bone density in elderly people with osteoporosis.


Psoriasis is defined as a chronic skin condition, which is caused by an overactive immune system.  Symptoms of psoriasis include flaking, inflammation, and thick, white, silver, or red patches of skin.  There is evidence that administering fish oil intravenously (by IV) can decrease the severity of psoriasis symptoms.  Also, applying fish oil to the skin also seems to improve symptoms of psoriasis.


Psychosis is a medical condition known to cause severe mental disorder.  During psychosis, thought and emotions become impaired and there is literally no conscious of what is happening in the surroundings. Research has shown that taking a fish oil supplement might help prevent psychotic illness in young adults and teenagers.

Raynaud syndrome

Raynaud disease causes numbness and cold in some areas of the body such as fingers and toes due to cold temperatures or stress.  There is some evidence that taking fish oil can improve cold tolerance in people with the usual form of Raynaud syndrome.

Rheumatoid arthritis (RA)

Rheumatoid arthritis (RA) is an autoimmune disease that can cause joint pain and damage throughout the body.  Taking fish oil by mouth, alone or together with the drug naproxen (Naprosyn), helps improve symptoms of rheumatoid arthritis.  Adding fish oil to the diet can reduce the use of pain medications associated with rheumatoid arthritis.  Also, administering fish oil intravenously (by IV) reduces swollen and tender joints in people with rheumatoid arthritis.


A stroke may be caused by a blocked artery called an ischemic stroke or the leaking or bursting of a blood vessel called a hemorrhagic stroke.  Moderate fish consumption, which is once or twice weekly seems to lower the risk of having a stroke by as much as 27%.

What happens when you overdose?

Fish oil is generally safe when consumed in appropriate quantities.  A high dose of fish oil can lead to some complications. Some of the side effects associated with fish oil include:

High blood sugar:  Research shows that supplementing with high amounts of omega 3 fatty acids could increase blood sugar levels.  This is because large doses of omega-3 fatty acids can stimulate the production of glucose, which can contribute to high levels of long-term blood sugar levels.

Bleeding:  Bleeding gums and nosebleeds are two of the main side effects of excess fish oil consumption.

Can lower the blood pressure:  Fish oil is known to lower the blood pressure.  The properties of fish oil can be beneficial for those with high blood pressure, but it can cause serious problems by further lowering the blood pressure for those who have low blood pressure.  Fish oil is also known to interact with blood pressure-lowering medications.

Diarrhea:  Diarrhea is one of the most common side effects associated with taking fish oil, and maybe especially prevalent while taking high doses.

Acid reflux:  Fish oil is high in fat and may cause acid reflux symptoms such as belching, nausea, indigestion, and heartburn in some people.

Stroke:  Studies have found that a high intake of omega-3 fatty acids could increase the risk of hemorrhagic stroke.

Vitamin A toxicity:  Many types of omega 3 fatty acid supplements that are available in the market are high in vitamin A and can lead to toxicity if consumed in large amounts.

Insomnia:  Moderate doses of fish oil have been shown to improve sleep quality, but studies also suggest that taking large amounts can cause insomnia.



Display this infographic on your website

Want to live a healthy lifestyle?

Subscribe to free FactDr newsletters.





If you're enjoying our website, we promise you'll absolutely love our new posts. Be the first one to get a copy!

Get factually correct, actionable tips delivered straight to your inbox once a week.

I want the latest scoop on :

We hate spam too. We will never share your email address with anyone. If you change your mind later, you can unsubscribe with just one click

By clicking Subscribe, I agree to the FactDr Terms & Conditions & Privacy Policy and understand that I may opt out of FactDr subscriptions at any time.




Top Stories