Fish oil: proven benefits, side-effects and pregnancy safety

Eat more fish and collect more benefits

fish oil

Fish oil is in reality fat extracted from the fish tissues or liver depending on the species. It is often referred to as omega-3 since its highly rich in these fatty acids. Unlike plants that only contain one type of omega-3 (ALA –  alpha-linolenic acid), fish oil provides two: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).

The first plays an important role in helping the body synthesize compounds that can trigger blood clots and inflammation, while the second is part of the structure of the eye and the brain.

The body cannot produce omega-3, so these important fatty acids need to come from an external source. Due to its richness fish oil is an excellent source, particularly if ingested by eating the fish, but supplements are not a bad option either.

Benefits of fish oil

fish oil benefits

Omega-3 fatty acids are essential to numerous body functions. By having an active role in the brain, the eyes and fighting inflammations, maintaining good levels of these acids is extremely important for the body general well-being.

Cardiovascular benefits

A 2018 meta-analysis of 10 different trials debunked the popular idea that omega-3 fatty acids can reduce the risk of cardiovascular disease.

However, even if their benefits aren’t as big as people used to believe, fish oil can still provide support to get a healthier heart. According to a 2013 overview of omega-3 therapies, both EPA and DHA have a direct effect lowering the triglyceride levels. In fact, the FDA has already more than one approved treatment using these fatty acid agents to treat the triglycerides with little side-effects.

Furthermore, these types of omega-3 have been shown to lower blood pressure, even on subjects with obesity, It should be noted, nonetheless, that dietary omega-3 presented better results than that of supplements.


The intake of fish oil has proved to have anti-inflammatory effects. In a 2017 research, the consumption of omega-3 showed potential to inhibit the secretion of inflammatory factors, while in a 2002 study, the intake of these fatty acids helped to reduce the symptoms of chronic inflammatory and autoimmune diseases.

In both instances, the researchers confirm the anti-inflammatory effect but admit that further studies are required to understand where this effect stems from as omega-3 can interfere with several processes.

Skin health

fish oil skin

Several studies have already been conducted to assess the effect of omega-3 fatty acids to treat different skin conditions such as psoriasis and acne. A 2012 critical review analyzed the main work in the area and concluded that most have contradicting results.

The only condition it was proved to be effective against was psoriasis. The original research showed that a supplementary treatment with omega-3 fatty acids reduced pruritus, scaling and scalp lesions. A more recent 2017 study also confirmed the positive results but admitted that it is necessary to better assess the ideal quantities of these fatty acids for each level of severity.

As for pruritus, a 2015 trial using fish oil for oral supplementation had already concluded that the omega-3 present in this oil could help treat this condition and dry skin by “reinforce and restore cutaneous integrity and function”.

Other possible benefits

Fish oil is associated with several other benefits. However, the studies on the matter seem to present contradictory results or are not suitable for comparison, which makes it hard to evaluate the efficiency of the oil and the doses required for it to be.


Different studies have been performed to assess the effect of an increased omega-3 intake for depression prevention and treatment. However, to date, the results have been conflicting.

In a 2015 review of scientific evidence, the researchers admit that the different findings could be caused by the specificities of each research.

They also recommend further studies evaluate if the causes of depression could also be influencing the results. If that’s the case, it would explain why depressed subjects with low omega-3 levels experienced an improvement, while others with balanced values of this fatty acid did not.

Psychiatric disorders

fish oil psychiatric

As with depression, the studies conducted so far regarding the use of fish oil – and omega-3 fatty acids in particular – to treat psychiatric disorders are not conclusive.

In a review of the main scientific literature published between 1980 and 2015, the researchers admit that, given the amount of positive results, there are strong indications that omega-3 could help with psychiatric disorders such as schizophrenia and bipolar disorders. However, the studies had too many different variables and factors between them, which renders their comparison impossible.

Eye diseases

The effect of omega-3 in the treatment of eye diseases is still a hot topic of debate and there is no middle ground.

The problem seems to be the different conditions it could act upon and the reason it does so. In a 2016 study, for instance, the researchers suggest that omega-3 could potentially help to treat dry macular degeneration. However, they could not be certain if this was due to the anti-inflammatory response of the fatty acids or if they intervened in other factors too.

In May 2018, a study published in The New England Journal of Medicine made the headlines by affirming that, as far as dry eye disease goes, omega-3 has the same effect as a placebo: none.

And yet, in the year before, a different study published in the Biomedicine Hub presented scientific proof that the anti-inflammatory effect of the fatty acids was enough to produce positive results for the treatment and prevention of several eye diseases, including dry eye.

Attention deficit and hyperactivity disorder (ADHD)

The publishing of a 2009 study casted light over the possible use of omega-3 to treat children with ADHD, as the controlled group taking this supplementation showed fewer symptoms. However, the authors already alerted back then to the necessity of further studies to assess the required doses and length of treatment.

A 2016 critical review also confirmed that the results of similar trials are inconsistent. All tests were positive only where there wasn’t a placebo group for comparison. Whenever this group was introduced the results become irregular.


fish oil dosage

To attain a good intake of omega-3 fatty acids, the American Heart Association recommends eating fish at least twice a week, especially mackerel, herring, sardines and salmon. This is a much better option than supplements since fish is also a good source of protein and it’s low in saturated fat.

As for supplements of fish oil, there isn’t a recommended dosage established. The guideline should be the content of omega-3 fatty acids each capsule contains, but not only this might vary depending on the brand, the ratio of EPA and DHA can also be different. Furthermore, different conditions such as high blood pressure or inflammation, require different quantities of fish oil to be effective.

Ideally, you should talk to your doctor before taking any fish oil supplements and ask for his advice regarding the dosage. If you decide to skip the doctor’s appointment, make sure to carefully follow any label instructions.


If you decided to take fish oil the old good way by eating more fish, then you don’t need to worry about side-effects. It would be very hard for you to consume enough fish to reach potentially dangerous quantities of this oil.

However, if you choose to take the fish oil supplements, there are a few things you should be paying attention to.

Individuals with diabetes

A 1989 study first raised awareness to the fact that an increased intake of omega-3 could affect the blood sugar levels and be potentially dangerous for individuals with diabetes without any added benefits.

However, further research presented inconsistent results. A 2015 research admits that omega-3 fatty acids might affect the glucose control and lipid levels but it is highly dependable of the ratio EPA/DHA.

A 2017 clinical trial, however, did not find any changes in the blood glucose levels or the lipid profile in subjects with diabetic dyslipidemia.


fish oil bleeding

An excessive intake of fish oil can prevent blood clot formation and result in bleeding. The most common symptoms are nosebleeds and bleeding gums.

If you take any blood thinners, talk to your doctor before deciding on trying fish oil supplements. Likewise, these supplements are not recommended prior to surgery.

Lower blood pressure

One of the effects of fish oil is lowering blood pressure but this is only a benefit if you suffer from hypertension. In healthy individuals, these supplements could lower blood pressure too much.

People already with low blood pressure are particularly more at risk.

Other side-effects from taking fish oil supplements

Even if not ingested in excess, fish oil supplements can still give rise to some side-effects, mostly due to the difficulty of the body to process such a large amount of ingredients at once.

Among the most common are:

  • Nausea
  • Vomiting
  • Rash
  • Diarrhea or loose stools
  • Fishy aftertaste and bad breath
  • Indigestion.

Is it safe to take fish oil supplements during pregnancy?

fish oil pregnant

Not only it is safe, according to a 2018 study, it is even advisable. In this research, women took fish oil supplements in the later stages of pregnancy and their babies’ growth was followed for 6 years. The researchers concluded that the fish oil had a positive impact on the children’s growth, as they presented increased lean mass, bone mass and fat mass.

During pregnancy is also the only time when it is preferable to ingest fish oil as a supplement and not through fresh fish. The latter might be contaminated with mercury, while the treatment required to produce the supplements filters environmental toxins.

Safety issues

Always purchase the fish oil supplement from a reputable and trustworthy retailer. The brand should also be able to provide a third-party evaluation of the safety and quality standards of the supplement and manufacturing process.

Pay attention to the smell and taste of the supplement too. Fresh and high-quality oil doesn’t have a fishy smell or taste. The oil only acquires those characteristics as it becomes rancid.

Your doctor should be the one indicating the daily intake due to the particularities of each pregnancy.