Fish Oil Supplements


Fish oil supplements are as effective as fish meat for providing EPA and DHA, but also offer convenience, with negligible contamination risks.

The recommended daily intake of EPA and DHA for healthy people could be met without taking supplements, by eating two portions per week of fatty fish such as salmon, mackerel or herring.

The recommended dose for people suffering from hypertriglyceridemia is much higher, and might best be achieved using fish oil supplements.

A Gift from the Sea: Fish oil supplements provide a convenient, effective and safe method for providing adequate quantities of EPA and DHA, the long chain n-3 PUFAs that are important for maintaining optimum health.


Extensive research material exists, based on many scientific studies, supporting the effectiveness of fish oil supplements. For this project we examined a number of published research articles and consulted some books. These information sources are listed in a table at the end of this page.

We formulated a series of questions which we have then attempted to answer by studying the research material. Some of the questions require further research in order to reach a firm conclusion. This reflects the general state of scientific enquiry into n-3 fatty acids, which has yet to unlock many doors. This is especially true of the specific physiological mechanisms that are responsible for widely observed effects.

The questions that we have addressed during this project are:

What is the optimum intake ratio of EPA to DHA?
What is the optimum daily dosage?
Is there a contamination issue?
Is there a sustainability issue?
Are fish oil supplements as effective as fish?
What side effects are there?
What specific benefits do they provide?
What factors reduce their effectiveness?
How long is it before they have an impact?
Are fish oil supplements available on prescription?

Much of the research relating to fish oil supplements also deals with fish meat and in many cases the material does not differentiate between n-3 PUFAs provided in supplement form and those provided by eating fish. This reinforces the notion that n-3 PUFAs from either source can be equally effective.

A tale of two reports

Two of the articles that we have examined are recent reviews of existing scientific studies concerned with the effect of n-3 PUFA consumption on cardiac arrhythmias.

The first, published by the American Heart Association (AHA) in its journal, Circulation, in 2007 covers dietary n-3 PUFAs as well as supplements.

The second, published by the British Medical Journal (BMJ) in 2009, covers only supplements but is also concerned with other medical outcomes in addition to arrhythmias.

The conclusions published by the two reports relating to arrhythmias were mildly conflicting. The BMJ review saw no evidence of a significant effect on arrhythmias, while the AHA review did. The BMJ review, however, reported a significant reduction in deaths from cardiac causes.

What is the optimum intake ratio of EPA to DHA?

Little information was found concerning this ratio and, in the majority of cases, doses are given as a combined quantity of EPA plus DHA.

The BMJ report (see above) suggested that, while the optimal fish oil dose is unknown, the formulation used in the large scale GISSI-Prevenzione trial, of 465mg EPA plus 386mg DHA, seems reasonable. This represents a ratio of 1.2 EPA to 1.0 DHA.

The ratio of EPA to DHA contained in the prescription-approved supplement P-OM3 (see below) is very similar, based on the specified content of 465mg EPA and 375 DHA.

The ratios of EPA and DHA found naturally in fish can vary significantly from one species to another. Obtaining adequate quantities of both PUFAs is likely to be far more important than the precise intake ratio achieved.

Menhaden oil is much higher in EPA than DHA while the opposite is true for Canadian Tuna (Lands 140).

Find more information about the EPA and DHA content of different fish

What is the optimum daily dosage?

What if I just ate Fish? According to the USDA, 100g of cooked Chinook salmon contains 1.73 grams of EPA plus DHA. You could therefore achieve the recommended daily input of 500mg of n-3 HUFA by eating one or two fillets of Chinook salmon per week.

Several studies quote a specific daily intake quantity of EPA and DHA combined, but do not specify the ratio between the two PUFAs. Different fish species can have significantly different ratios.

It is not clear why combined quantities are quoted without specifying the amount of each PUFA (or ratio). This could be related to the fact that EPA and DHA are typically found together in fish in varying ratios, although it is now possible to separate the two PUFAs and incorporate them into products individually or in pre-specified ratios.

Recommended combined quantities for protection against CVD fell in the range of 250mg to 500mg per day, with progressively smaller reductions in risk predicted for quantities greater than 500mg. ISSFAL have formally recommended a minimum of 500mg per day, again without specifying the breakdown between EPA and DHA.

A much higher daily dosage of combined EPA plus DHA is specified as a therapy for hypertriglyceridemia, a major risk factor for CVD and other degenerative diseases, at 2g-4g per day.

Pregnant women are advised to consume a minimum of 200mg of DHA per day in order to support neural and cognitive development in the unborn child.

The work of William E M Lands provides evidence that required intake levels of EPA and DHA can be reduced when dietary intake of the n-6 PUFA LA is reduced.

For doses greater than 1000g combined EPA plus DHA, caution is warranted where asthma, diabetes or blood clotting disorders are present.

William E M Lands has developed a mathematical model that can be used to calculate tissue PUFA composition for any given set of PUFA dietary inputs.

Find out more about the Lands calculator and application

Is there a contamination issue?

Critics of fish consumption assert that all fish are contaminated with harmful compounds that include methylmercury, dioxins and polychlorinated biphenyls (PCBs). It is widely accepted that these contaminants are present in fish and that they are generally more concentrated in larger fish, which are higher in the food chain.

According to Medline Plus, an online service operated by the National Institutes of Health (NIH), methylmercury contamination is greater in fish meat than fish oil and fish oil supplements contain almost no mercury. Apparently the purification process used in fish oil extraction eliminates most of the contaminants

Some studies suggest strongly that the health benefits of fish significantly outweigh the risk from contaminants. No study has yet been found by us that offers the opposite viewpoint.

Is there a sustainability issue?

Where did my Fish Oil come from? We need to know the extent to which the fish used to make our supplements came from a sustainable source. Sustainability of fish supplies is an important and complex issue that deserves our attention.

None of the research articles that we consulted expressed a view on sustainability. It is clear to us that anyone who eats fish or takes fish oil supplements should be concerned about sustainability of fish supplies. Full treatment of this important subject is outside the scope of this project but will in the future be covered elsewhere on our website.

Are fish oil supplements as effective as fish?

While this fundamental question was not directly addressed in most of the research studies reviewed, there is a general inference that fish oil supplements are as effective as fish in providing the health benefits associated with n-3 highly unsaturated fatty acids (HUFAs).

The lack of any negative scientific evidence concerning the efficacy of fish oil supplements (assuming that they are of adequate quality) strongly reinforces the idea that they can be used interchangeably with fish. This is indeed the approach taken in a number of the scientific studies.

Artemis Simopoulos, in The Omega Diet, makes it clear that supplements and fish are both equally effective dietary sources of EPA and DHA.

What side effects are there?

ISSFAL states there are no significant side effects for fish oils up to daily doses of 1g DHA or 2.7g EPA plus DHA.

For the prescription-approved supplement P-OM3 (see below) side effects recorded during clinical trials are negligible. P-OM3 does not have any known, clinically significant drug interactions. Clinical trial data suggest that P-OM3 does not increase clinical bleeding. LDL-Cholesterol levels can, however, be raised.

According to Sadovsky, studies using FDA-approved dosages of P-OM3 have not substantiated various myths surrounding the negative effects of n-3 PUFA.

Concerns of increased risk of bleeding due to the anti-thrombotic effects of fish oils are not supported by the evidence from clinical trials.

What specific benefits do they provide?

The most widely researched benefits of fish oil supplements are those related to cardiovascular disease, which are believed to be provided through the effects of EPA and DHA on atherosclerosis, thrombosis and cardiac arrhythmias.

EPA and DHA are known to reduce triglyceride levels and this is considered a key factor in preventing hypertriglyceredemia and hence pancreatitis. It may also be a factor in the prevention of cardiovascular disease.

Higher DHA levels in pregnant women are thought to improve a range of cognitive functions and promote other positive neural effects in the unborn child.

Both EPA and DHA are known to exhibit powerful anti-inflammatory effects, which are believed to help prevent several serious degenerative diseases.

What factors reduce their effectiveness?

How can we optimize use of the EPA and DHA that we consume? We should maintain a healthy n-3 to n-6 intake ratio by restricting our consumption of n-6 LA and AA and by consuming at least the recommended quantities of n-3 ALA, EPA and DHA.

The effectiveness of n-3 HUFA (EPA and DHA), whether consumed as supplements or food, depends on two related factors.

It depends on the proportion of n-6 in the body's total HUFA, effectively the ratio of AA (n-6) to the total of EPA plus DHA (n-3). This is heavily influenced by EPA and DHA consumption, because AA levels remain fairly constant regardless of diet (Muskiet), whereas dietary EPA and DHA are readily incorporated into tissue PUFA.

It also depends on the amount of LA consumed in the diet, with lower LA resulting in higher n-3 HUFA effectiveness, especially when ALA intake is also increased.

William E M Lands has developed an empirical model for predicting the likely tissue n-6 HUFA level (as a percentage of n-3 plus n-6) that will result from any dietary input permutation of four primary PUFA types. In collaboration with the website, Professor Lands has developed a calculator and application, both of which are freely available for public use.

Find out more about the Lands calculator and application

How long is it before they have an impact?

DHA is rapidly incorporated into most body tissues.

The rate of incorporation of DHA into the brain is much slower and, according to Professor Norman Salem, the highly unsaturated fatty acid (HUFA) composition of the brain does not respond readily to changed dietary PUFA intake. This is in spite of DHA accumulating in the brain preferentially over other tissues.

Thus, although DHA is present in the brain in higher concentrations than in other tissues, and at higher levels than other PUFAs, it takes some considerable time for dietary DHA to be incorporated into brain cell membranes.

Are fish oil supplements available on prescription?

P-OM3, manufactured by Lovaza, is a supplement containing 465mg EPA and 375 mg DHA, with 6 IU of vitamin E per 1g capsule. It is approved by the Food and Drug Administration (FDA) for use in adults with triglyceride levels greater than 500mg per dl. It is approved for use as a therapy on its own or in conjunction with statins, at a dose of 4g per day.

P-OM3 has also been approved for prescription use in Europe for more than a decade.

Because it has been approved by the FDA and other government health authorities, P-OM3 has been selected as the subject for several clinical trials.

P-OM3 is more highly purified and concentrated than many fish oil supplements that have not received prescription approval. Reported adverse effects are very mild in nature.