Fish oil: Benefits, side-effects, research and dosage

Fish oil is one of the most popular supplements today – and with good reason.

It is rich in omega-3 fatty acids. These fatty acids are categorised as essential fatty acids and have been associated with improvements in health. 

Although omega-3 fatty acids are highly needed in the body, our cells do not produce these beneficial fatty acids. Instead, one needs to consume these acids from one’s diet. 

What are omega-3 fatty acids? 

Omega-3 fatty acids can be sourced from flaxseed, fish, and dietary supplements such as fish oil. The main components of omega-3 fatty acids include eicosapentaenoic acid (EPA), alpha-linolenic acid (ALA), and docosahexaenoic acid (DHA) [1].

Plant oils are rich sources of ALA. These plant oils include canola, soybean, and flaxseed oils.

The good news is you can easily buy these healthy sources of ALA. All these oils are readily available in the market. Meanwhile, seafood and fish are excellent DHA and EPA sources [2]. 

Difference between essential and non-essential fatty acids? 

Do you know that our body naturally produces some fatty acids? Essential fatty acids are coined as critical since these are not naturally produced in the body. You must eat fruits, vegetables, meat, fish and seafood, and oil to increase the amount of these fatty acids in your body. 

In contrast, non-essential fatty acids are naturally produced in the body. Hence, it is called non-essential since there is no need to take supplements or food containing these fatty acids. However, when your body cannot cope with the demands of producing these natural fatty acids, you would need to source these fatty acids from supplements or the food you eat. 

Alpha-linolenic acid is an example of an essential fatty acid since it is not naturally produced in the body. You can get ALA from the beverages you drink and the food you eat daily.

Once inside the body, ALA is converted first into eicosapentaenoic acid (EPA) and then into docosahexaenoic acid (DHA). However, the concerning news is that the conversion of ALA to EPA and DHA is often inadequate. Therefore, eating foods and vegetables rich in ALA is necessary. 

The only practical way to raise the levels of omega-3 fatty acids is to take dietary supplements and eat healthy foods and fruits [3]. Getting DHA and EPA from the food we eat is the only feasible way to increase omega-3 fatty acids in the body. 

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What are the benefits of fish oil ? 

Fish oil is extracted from seafoods, specifically from the the tissue of the fish. The following are some examples of fish rich in fish oil: 

  • Anchovies 
  • Tuna
  • Herring 
  • Mackerel 

In addition, fish oil can be sourced from the livers of certain fishes. For instance, cod liver oil is an example of oil extracted from the liver of cod fish. 

Benefits of fish oil backed by evidence from research studies 

Lowers risk of heart disease

The primary omega-3 fatty acids, DHA and EPA, are found in fish oil and fish. The American Heart Association (AHA) has recommended taking fish and fish oil as part of your diet to reduce cardiovascular events such as stroke or heart attack in patients who already have CVD or cardiovascular disease [4]. Hence, a diet rich in omega-3 fatty acids is highly recommended. You can take omega-3 fatty acids through fish oil supplements when your diet is insufficient. 

A clinical trial [5] enrolled a total of 8000 patients from different healthcare centres, making this study a multi-centre study. In clinical trials, recruiting patients from multiple centres increases the heterogeneity or representativeness of the participants of the study.

Recruiting patients from different hospitals or health centres is critical since this reduces the risk of bias. Bias can occur when there are fewer samples, and results might be due to chance. 

All patients in the clinical trial [5] had an increased risk of cardiovascular disease and had high blood triglyceride levels. Half of the participants were enrolled in the experimental group, while the other half were in the placebo group.

The first half received 2 grams of Vascepa, a purified EPA supplement, twice daily. The other half, or the placebo group, received supplements containing only mineral oil. 

Results of the clinical trial revealed that those who received 2 grams of fish oil significantly reduced their risk of stroke, heart attack and death compared to the placebo group. Notably, triglyceride levels were reduced in those who received fish oil supplements compared to the control group. The supplement also reduced the need for a heart procedure to open clogged arteries. 

A meta-analysis [6] likewise supported the findings of the clinical trial. A total of 10 studies were included in the meta-analysis, and the results were consistent across the studies. Fish oil supplements lowered the risk of heart attack due to coronary heart disease and death. 

Reduces symptoms of depression and anxiety 

Depression and anxiety remain to be among the most common mental health condition across the world. Symptoms of depression include lethargy, extreme sadness, inability to function in activities of daily living, and general loss of interest in life [7]. Anxiety is characterised by constant nervousness and worries [8]. 

A review [9] reported that the intake of fish oil supplements with omega-3 fatty acids was associated with reduced symptoms of depression. However, there were some conflicting results, with some studies suggesting no strong association between omega-3 fatty acids supplements and depression. It is acknowledged that in studies that found little to no association, the patient’s social environment and overall diet might explain the lack of association. 

In another meta-analysis of studies [10], omega-3 fatty acids were significantly associated with reduced symptoms of depression. Interestingly, omega-3 fatty acids also reduce symptoms of bipolar disorder. However, there is a need to verify these findings in more extensive trials in the future. 

Notably, the same findings can also be seen in patients with anxiety. Evidence [11] from the literature revealed that regular consumption of omega-3 fatty acids reduced stress levels. Although the findings are promising, there is still a need to verify results in more extensive clinical trials. 

The benefits of omega-3 fatty acids in improving mood are also seen in younger children. For example, one review [12] showed that for children, omega-3 fatty acids were beneficial in reducing symptoms of depression. Hence, regular supplementation of omega-3 fatty acids may answer the constant low mood in young children and young people. Harnessing the benefits of omega-3 fatty acids in reducing depression could help children and adults enjoy better mental health. 

Improves brain health of infants and children 

Do you know that omega-3 fatty acids are highly needed to develop the infant’s brain? If you are pregnant or planning to be pregnant, you might want to learn how omega-3 fatty acids benefit your child’s brain development and health. 

About 40% of the polyunsaturated fatty acids in the brain are composed of DHA, while 60% of the polyunsaturated fatty acids in the eye retina are composed of DHA [13]. 

Another emerging study [14] reported that brain function improved after the intake of omega-3 fatty acids in children. Specifically, memory, learning and brain development improved. Findings from this study provide evidence that omega-3 fatty acids have the potential to improve brain health and functioning in young children. 

A six-month study that recruited more than 180 children aged 7-9 years old revealed that eating fish-flour bread spread rich in omega-3 fatty acids improved brain functioning. The children improved memory and learning when supplemented with omega-3 fatty acids in fish-flour bread spread. It is important to note that children in the experimental group ate fish flour bread rich in omega-3 fatty acids for six months. 

Although it is believed that DHA and EPA are best given during children’s formative years, the effects of omega-3 fatty acids appear to continue even for older children. For example, another study [15] that recruited healthy boys aged 8-10 assigned these children to a control and experimental group.

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The control group received a placebo; the first experimental group received 400 mg of omega-3 fatty acids, while the second experimental group was administered 800 mg of omega-3 fatty acids daily. At the end of the eight-week study, findings indicated that both experimental groups demonstrated significant improvements in reaction time and improved attention span of the boys.

Further, prefrontal cortex activity also increased. This brain area is responsible for impulse control, attention, and planning. These findings provide additional evidence of the benefits of DHA and omega-3 fatty acids in improving the brain function of young to older children. 

While the evidence is not yet strong, and more studies are needed to verify the findings of these studies, these results are all promising. It would mean that for children in their formative years, the power of omega-3 fatty acids in improving brain functioning continues. This is good news for mothers and fathers who want the best for their children’s brain development. 

Lowers risk of stroke 

Stroke is one of the most common causes of death across the world. However, this condition can be prevented by eating the right food, taking the right supplements, and exercising. 

A report from the Agency for Healthcare Research and Quality (AHRQ) stated that there is still no strong evidence from published sources that omega-3 fatty acids can reduce total deaths from stroke or total strokes [16].  

However, there is evidence that eating seafood such as shellfish and fish can lower the risk of stroke, specifically ischemic stroke. This type of stroke is caused by blockage or narrowing of the blood vessels in the brain [16]. 

Helps manage triglyceride levels

Triglycerides are found in the body and are needed to build new cells or tissues. However, when present in excess amounts, the accumulation of triglycerides can result in several health conditions, including stroke and heart disease. 

To lower triglycerides, it is recommended that a diet high in fibre, fruits, and vegetables and low in fats is recommended. Increasing physical activities, such as engaging in routine exercises, are also needed to lower triglycerides. However, some individuals would require medications to lower triglycerides. 

The good news is you can take omega-3 fatty acids found in fish oil to lower triglycerides. It has been shown that omega-3 fatty acids in high doses can lower triglycerides [16]. Fish oil supplements also help manage triglycerides in combination with diet and exercise. 

Reduces risk of cognitive impairment and Alzheimer’s Disease 

Alzheimer’s disease is one of the more common health conditions manifested in older adulthood. Although it is not a disease caused by ageing, its prevalence is highest in older adults. A marked decline in cognition displays this condition. Hence, patients with Alzheimer’s disease suffer from mild to severe cognitive impairment. 

A few research studies [16] reported that regular intake of fish or shellfish in the diet reduced the risk of cognitive decline. Omega-3 fatty acids present in these foods have been shown to improve cognition in older adults. However, there are still no extensive, population-based studies confirming that omega-3 fatty acids can prevent the occurrence of Alzheimer’s disease or prevent cognitive decline. 

The lack of studies supporting the effectiveness of omega-3 fatty acids in preventing Alzheimer’s disease or cognitive decline may be due to difficulties in recruiting a large population of patients and determining the effects of omega-3 fatty acids over time. Further, Alzheimer’s disease is a multi-factorial disease. Improving levels of omega-3 fatty acids in the body might not fully address several mechanisms that can lead to cognitive decline. 

Individuals’ genetic backgrounds may also influence the effectiveness of omega-3 fatty acids [16]. It is suggested that before developing Alzheimer’s disease, individuals with the APOE4 gene may benefit from omega-3 fatty acids supplementation.

However, when omega-3 fatty acids are taken after the onset of Alzheimer’s disease, this may no longer prevent cognitive decline. The APOE4 gene has been associated with an increased risk of Alzheimer’s disease. 

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Helps manage metabolic syndrome 

Metabolic syndrome is a health condition that can increase the risk of cardiovascular disease and diabetes. Symptoms associated with metabolic syndrome include high triglycerides, insulin resistance, high blood pressure and low levels of good cholesterol. Further, those with metabolic syndrome have excess belly fat or central obesity. 

Fish oil supplements may be beneficial since they can help manage the metabolic syndrome. 

One study [17] demonstrated that in obese adolescents, regular administration of omega-3 fatty acids lowered inflammation and improved vascular function. Participants in the experimental group received 1.2grams of omega-3 fatty acids daily for three months.

Although the study did not find any significant difference in the blood pressure between the experimental and control groups, the results were still substantial since these demonstrated the effects of omega-3 fatty acids in improving vascular function and reducing inflammation. When chronic inflammation is present, this can increase the risk of developing stroke and heart disease [17]. 

Improves symptoms of autoimmune diseases 

Autoimmune diseases are conditions where your immune system mistakenly attacks your cells and treat these as foreign bodies. 

There is evidence [18] from the literature that omega-3 fatty acid supplementation can fight off an autoimmune disorder called psoriasis. Patients in the study were treated with omega 3-fatty acids and topical steroids. Results indicated that those in the experimental group significantly improved the psoriasis severity index and quality of life index. There were improvements in the following:

  • Pruritus and scalp lesions
  • Scaling
  • Erythema or reddening of the area
  • Infiltration of treated areas

Although the study had a small sample size, the results were favourable and promising. This is another evidence that omega-3 fatty acids can help manage autoimmune disorders. 

Another study [19] likewise showed that omega-3 fatty acids could help manage ulcerative colitis, another autoimmune disorder. However, the research was a case study, and the findings could not apply to a broader group of patients with ulcerative colitis. There is a need to verify findings in more extensive trials in the future.

Despite the limitation of the study, results were also promising since this showed the potential of omega-3 fatty acids in lessening the symptoms of ulcerative colitis. Since most drugs used to treat ulcerative colitis may be toxic, finding an alternative supplement can help reduce the risk of adverse events. 

Protects skin from UV damage

One of the structural components of the skin is DHA. Omega-3 fatty acids are responsible for maintaining the health of the cell membranes of the skin cells. 

When cell membranes are healthy, this results in moist, soft, and supple skin. Here are some benefits of omega-3 fatty acids in the skin: 

  • Hydration of the skin and managing oil production 
  • Improving skin suppleness and preventing premature ageing 
  • Preventing hair follicles from hyperkeratinization 
  • Reducing acne risk 

The good news is you can take omega-3 fatty acids supplements to protect yourself from the effects of UV rays from the sun. When UV rays hit the skin, this can result in skin damage since too much UV exposure can release substances that destroy collagen in the skin. Omega-3 fatty acids, particularly EPA, will help block the production of enzymes that disintegrates collagen. 

What happens if I don’t have enough omega-3 fatty acids? 

A deficiency of omega-3 fatty acids can result in the following: 

  • Itchy rash 
  • Red, swollen skin 
  • Scaly skin 
  • Rough skin 

Is it safe to take omega-3 fatty acids? 

The safety of omega-3 fatty acids has been shown in research. However, there are rare cases when individuals may develop side effects. You might want to consider the following before taking omega-3 fatty acid supplements: 

  • If you are taking medications that affect blood clotting, it is best to consult your doctor before taking omega-3 fatty acids.
  • If you have known allergies to fish or shellfish, talk to your doctor before taking over-the-counter omega-3 fatty acids. 


The appropriate dose of omega-3 fatty acids would be dependent on your need. Recommended amounts vary between health conditions and unique circumstances. 

Pregnant and nursing women 

Pregnant and nursing women are recommended to take sufficient omega 3-fatty acids to ensure optimal brain development of their children. A study [13] emphasized the importance of DHA in developing infants’ central nervous system and retina.

Since most brain development and growth occurs when the fetus grows inside the mother’s body, pregnant mothers must receive sufficient DHA or omega-3 fatty acids in their diet. The child must take appropriate amounts of DHA since brain development continues from childbirth until about 5 to 6 years of age.

Infants who are breastfed could also receive DHA through their mother’s milk. Hence, it is recommended for pregnant and breastfeeding mothers to take at least 100-300 mg of DHA and 2.6 g of omega-3 fatty acids daily [13]. 

Follow-up of infants whose mothers took DHA and omega-3 fatty acids supplements demonstrated the following: 

  • Higher mental processing scores 
  • Better eye-hand coordination at four years of age 
  • Higher psychomotor development

Infants and children 

Children who took DHA and EPAs supplementation during preschool years demonstrated the following: 

  • Enhanced academic performance 
  • Enhanced learning capability 
  • Prevention of attention deficit hyperactivity disorder (ADHD)

The National Institutes of Health [20] recommend these doses for children: 

  • For infants at birth until 12 months, recommended amount of ALA is 0.5g/day. 
  • For children who are 1-3 years, the recommended dose is 0.7 g/day. 
  • Children 4-8 years old should take 0.9g/day of ALA. 


In adolescents, omega-3 fatty acids taken at 1.2 grams daily for three months be safe with no known adverse effects or adverse events. This dose is within the safe range and can be taken for months [17]. 

It is still best to consult your doctor for any potential drug-to-drug interaction when taking fish oil supplements high in omega-3 fatty acids. Always inform your doctor if you are taking other medications to prevent any adverse effects.

For example, a drug-to-drug interaction might occur when taking omega-3 supplements and medicines that affect blood clotting. When you are allergic to fish and shellfish, taking fish oil capsules might not be safe. Allergic reactions may result in bronchoconstriction or inflammation of the skin. 

What are the side effects of omega-3 fatty acids? 

Despite the general safety of omega-3 fatty acids as a supplement, there are still some recorded side effects. Some of these include the following: 

  • Bad-smelling sweat
  • Bad breath
  • Headache 
  • Nausea
  • Diarrhoea 
  • Heartburn 
  • Unpleasant taste 

However, most of these side effects are mild, and no recorded adverse events exist. 

Overall, omega-3 fatty acids are associated with many health benefits. These improvements range from improvements in skin conditions to managing the autoimmune disorder.

All these health benefits are within your reach. Choosing the most appropriate fish oil supplement rich in omega-3 fatty acids can help you in your journey to longevity, health, and wellness. 

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