While several studies have suggested that higher omega-3 intake could lower the risk of heart disease, others have concluded that no significant effect of omega-3 on heart health has been observed.
A recent JAMA review had reported that "omega-3 fatty acids had no significant association with fatal or non-fatal coronary heart disease or any major vascular events".
Dr Bill Harris, founder and president of omega-3 index testing lab OmegaQuant, pointed out several flaws in such studies.
Impeded by insufficient intake
He told NutraIngredients-Asia: "The problem is that many such studies give a low dose of omega-3 to participants, so any effect on cardiovascular health is minimal.
"People these days are generally taking more omega-3 in their diets, so those in the placebo groups in such studies are already consuming almost as much as those in the treatment groups."
He said the recommended daily dose of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) was 1.5g, but most trial subjects were given below 1mg each daily.
He also emphasised the importance of EPA and DHA, saying that plant sources of omega-3 provide alpha-linoleic acid (ALA) but do not have much impact on overall omega-3 levels.
Oily fish such as mackerel, salmon, sardine, herring and tuna, he said, were the best sources of EPA and DHA.
"If you are not taking EPA and DHA, you are not increasing your omega-3 index."
He added that omega-3's ability to help reduce general inflammation, prevent arrhythmia, lower the risk of blood clots by preventing platelets from sticking together, lower blood pressure and triglyceride levels, and improve vascular function by causing blood vessels to react more quickly and regularly to changes in pressure point to its heart health benefits.
He further said: "There's also a difference in accuracy and the depth of information between RCTs and epidemiological studies.
"The best way to put yourself in a cardio-protective zone is to make sure your omega-3 index is around 8%, but RCTs are giving subjects only 6%."
However, two clinical trials could paint a clearer picture of the link between omega-3 intake and heart health.
The first is the Amarin Pharma-sponsored REDUCE-IT, conducted by researchers at American, French, Canadian and UK institutes and organisations, including Harvard Medical School, the Royal Brompton Hospital, Université Paris-Diderot, and the Montreal Heart Institute.
The trial involves male and female heart disease patients aged 45 and older, as well as men and women aged 50 and above with diabetes and another risk factor; there are about 8,000 participants in total.
Subjects were given either a placebo, or icosapent ethyl, a highly purified EPA ethyl ester. The trial's main objective was to determine if treatment with icosapent ethyl reduces ischaemic events in statin-treated patients with high triglyceride levels and elevated heart disease risk.
The study started in November 2011 and was due for completion in December 2017, with a full report still pending.
The second is STRENGTH, led by The Cleveland Clinic and sponsored by biopharmaceutical firm AstraZeneca.
It involves 13,000 patients aged 18 and above with hypertriglyceridemia, low-HDL and high cardiovascular disease risk, being given either statin and a corn oil placebo, or statin and Epanova, a drug made from omega-3 carboxylic acids.
The primary outcome measure is the time to the first occurrence of any major adverse cardiovascular events, such as cardiovascular death, non-fatal stroke, or hospitalisation for unstable angina.
The secondary outcome measure is the cardiovascular events, including the first occurrence of cardiovascular death, and non-fatal stroke.
The trial started in October 2014 and is due to be completed by October 2019.
Harris was speaking to us from Sydney, where he met with Aker BioMarine and DSM customers to discuss the Omega-3 Index Project, which aims to raise awareness of the benefits of omega-3 and the health issues arising from its insufficiency.
It encourages people to use the Omega-3 Index test to identify their omega-3 status and take the necessary steps to ensure sufficiency, and avoid chronic disease risk.
He revealed that OmegaQuant is working directly with brands to find ways to use the Omega-3 Index text to support their marketing and sales efforts, and increase customer interest in their omega-3 products.