Fish oil supplements in New Zealand

Are NZ fish oil supplements safe, true to label and can they provide a health benefit? Professor Julia Rucklidge investigates these important questions.

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Are NZ fish oil supplements safe, true to label and can they provide a health benefit?

I recently co-authored an article in the New Zealand Medical Journal looking at whether omega-3 fatty acids contained in 10 fish oil supplements sold in NZ are true to label, accurate with health claims and safe to consume. Overall, although likely to be safe (no detected mercury) and accurate in content of fish oil, many may not be accurate in the stated health benefits.

What Are Omega-3 Fatty Acids?

Omega-3 fatty acids are important in cells, they are key components of cell membranes and ensure the proper function of the membrane. Humans are unable to biosynthesise omega-3 fatty acids and so we must obtained them via our food.  While it is impossible not to obtain some omega-3 fatty acids with food, it is feasible that too little might be consumed at important points in growth and development, or that some people might require more omega-3s than others which could lead to a greater risk of some diseases or disorders.

Omega-3 fatty acids are found at high levels in oily fish and shellfish, plant and nut oils, flaxseed, walnuts and some algae oils. These foods can be used to boost omega-3 intake. In addition, omega-3-rich oils can be extracted from nature’s rich sources (e.g. oily fish, krill, flaxseed) and used as dietary supplements.

There are two main types of omega-3 fatty acids or essential fatty acids (EFAs): EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). It is important to note that the amount of EPA+DHA is often quite a bit lower than the amount of total EFAs stated at the front of the bottle. For example, the front of the label might state each capsule contains 2000mg of purified natural fish oil BUT on the back you learn that only provides 360mg EPA and 240mg DHA. So you need to read the entire label to determine the amount of the active ingredients.

Are labels accurate?

Research into accuracy of labels is not a new idea in the supplement world. A few years ago, international headlines were made based on a study of 32 NZ fish oil brands, showing that only 3 of them had the stated amount of EPA and DHA as stipulated on the bottle. We were therefore surprised when we found that 90% of the 10 products we studied, were accurate in terms of amount of EPA and DHA. This is good news for the industry.

For our research, we took this work one step further. We also wondered about the accuracy of health benefits stated on bottles and websites. The health benefits stipulated across the 10 supplements were similar, with all of them reporting promotion of heart health, joint health, and brain function on the labels and/or manufacturer websites. DHA and EPA doses are particularly important for these health benefits. Stated benefits varied from “assists in the maintenance of healthy brain function” to “helps during times of stress and emotional upset” to “keeping your heart healthy” to “easing many kinds of inflammation, including joint swelling and stiffness”.

By law, because supplements are classified as foods and regulated under the Dietary Supplements Regulations 1985, the label cannot stipulate a therapeutic claim and therefore, interpretation of the intention of the stated health benefit tends to be obscured and vague.

What is the difference between a health claim and a therapeutic claim?

A health claim is quite different from a therapeutic claim. A therapeutic claim, as defined in the NZ Medicines Act (but similar definitions will exist in other countries as well), is quite far reaching and refers to preventing, alleviating, curing and treating diseases, ailments, defects and injuries.

In contrast, a health claim can mean a number of things but is generally limited to the maintenance or promotion of health or wellness. A health claim cannot assert a cure for an ailment. For example, a health claim could be: “Relieves the symptoms of arthritis” versus a therapeutic claim which would be “treats or cures arthritis”.

When it comes to the health benefits asserted on the bottles of fish oil supplements, that is they improve heart, joint and brain health, we had to wonder – what exactly does this mean and how did they measure it? How do you know a fish oil capsule has improved brain health?

We concluded that the only way to verify the health claims was through clinical trials looking at the effect of fish oils on brain function. Having said that, even if a clinical trial showed that a fish oil supplement conferred a therapeutic benefit, unless the company chose to register the fish oil as a medicine (with no real incentive to do this as fish oil supplements cannot be patented), despite the positive trials, they cannot legally make that therapeutic claim on the bottle. So they have to stick with a health claim that is vague and generally unhelpful to the consumer. This is why labels on supplements are so vague, because otherwise they would be in trouble with the law.

Can EFAs improve brain, cardiovascular and joint health?

As far as we are aware, clinical trials aimed at brain health investigate whether the supplement has improved brain function – that is improved mood, or attention, or anxiety. Therefore, we delved into the literature that investigates whether fish oils can improve mental health. We found that the most consistent findings of possible benefit were for mood (depression) and attention (ADHD). No other area of mental health had reliable data showing benefit from the consumption of EFAs.

The optimal dose to improve mood has been determined to be 1-2 grams of EPA+DHA. We found that the EPA dose needs to be greater than 500mg in order to confer a notable benefit in the symptoms associated with ADHD. Please note though, that there is considerable variability in the findings in these areas.

It is important to note that in clinical trials, investigators typically report on group differences on means of the groups (usually fish oil versus placebo) and so even if the fish oil is found to be better than placebo, this DOESN’T mean that everyone in that group benefitted. Some did, some didn’t.

For heart health, the research generally shows that 1 gram is sufficient to benefit cardiovascular health after a myocardial infarction.

Finally, 2.7 grams of EPA+DHA was the minimum amount required to improve painful or tender joints.

So yes, fish oils can improve health although you can see that the details above really are about therapeutic claims (ie treating a disease like treating ADHD). However, one could argue that improving a symptom is a health benefit (supporting concentration). Hopefully, you see the problem.

What did we find?

We looked at accuracy of product labels of 10 over-the-counter fish oil supplements, both in terms of amounts of omega 3 content (EPA/DHA) and health claims. We found:

Product labels for 90% of the supplements were accurate with respect to EPA/DHA content, whereas the remainder 10% (1 product) contained between 12% of amounts stated on labels.

All products taken at the highest recommended daily dose contained more than 500 mg of EPA and as such could support symptoms associated with ADHD, 80% of them taken at this highest dose would contained the minimal dose (≥1 g EPA+DHA) identified for supporting mood, 80% of the products had doses comparable to the recommended dose for heart health (≥1 g EPA+DHA), and 30% contained the optimal dose for assisting with joint health (≥2.7 g EPA+DHA).

Based on the lowest recommended daily doses, 50% were in the range necessary to confer a benefit for symptoms associated with ADHD, 20% were in the dose range for heart health and mood, and 30% were in the dose range for joints.

Based on the maximum number of capsules recommended (which ranged from 3 to 6 capsules), only three products would likely confer the dose identified as optimal for achieving a health benefit across all three health areas. Only two products recommended doses that would likely confer a health benefit both at the minimum and maximum number of capsules. More products would likely benefit brain and heart health than joint health.

What did we learn about risks?

The main health risks associated with fish oil supplements has to do with mercury and possible oxidation but the latter is hard to assess. We measured mercury content in the capsules. Mercury was not detected in any of the products which indicates that they are not likely to confer any harm in consuming them.

Take away

This study shows that the majority of the most popular fish oil supplements in New Zealand are true to label in terms of doses, but not in terms of potential health benefits, although it is important to note that no supplement claims to treat mental illness or other illnesses.

However, the risk of mercury toxicity is negligible and therefore, while they may not confer a health benefit, they do appear to be safe to consume.

What does this all mean for the consumer?

Read the bottle and take the maximum number of capsules stated if you want to have any chance of experiencing a benefit for the health condition you are using it for.

If not treating anything, then a lower dose might be sufficient to maintain good health.

Allow time for them to work.

Choose products with a higher DHA/EPA dose stated per capsule.

You can feel assured though, that while the capsules might not help, you won’t be consuming mercury.


Julia Rucklidge is a Professor of Clinical Psychology in UC’s School of Psychology, Speech and Hearing and the Director of Te Puna Toiora: Mental Health and Nutrition Research Group.