Increased consumption of omega 3 fats via supplements offers little or no protection on cardiovascular diseases, according to a new review of clinical evidence, led by UK researchers.
Those behind the new Cochrane systematic review, published this week, said it challenged the widely held belief that omega 3 supplements reduce risk of heart disease, stroke or death.
“The findings of this review go against the popular belief that long-chain omega 3 supplements protect the heart”
They noted that increased consumption of omega 3 fats was widely promoted globally and they were readily available and bought as over-the-counter supplements.
The main types of omega 3 fatty acids are alphalinolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). ALA is normally found in fats from plant foods, while EPA and DHA – collectively called long chain omega 3 fats – are naturally found in fatty fish.
The review combined the results of 79 trials involving 112,059 people, recruiting men and women, some healthy and others with existing illnesses, from North America, Europe, Australia and Asia.
The studies included in the review assessed the effects on diseases of the heart and circulation of consuming additional omega 3 fat for at least a year, compared to usual or lower omega 3.
Most studies investigated the impact of giving a long-chain omega 3 supplement in a capsule form and compared it to a dummy pill. Only a few assessed whole fish intake, noted the reviewers.
“This review did find moderate evidence that ALA may be slightly protective of some diseases of the heart and circulation”
Most ALA trials added omega 3 fats to foods such as margarine and gave such foods, or naturally ALA-rich foods such as walnuts, to intervention groups, and usual, non-enriched foods to other participants.
The Cochrane researchers found that increasing long-chain omega 3 provided little if any benefit on most outcomes that they looked at.
They found high certainty evidence that long-chain omega 3 fats had little or no meaningful effect on the risk of death from any cause.
The risk of death from any cause was 8.8% in people who had increased their intake of omega 3 fats, compared with 9% in people in the control groups, said the researchers.
They also found that taking more long-chain omega 3 fats, primarily through supplements probably made little or no difference to risk of cardiovascular events, coronary heart deaths, coronary heart disease events, stroke or heart irregularities.
In contrast, long-chain omega 3 fats probably did reduce some blood fats, triglycerides and HDL cholesterol. Reducing triglycerides was likely to be protective of heart diseases, but reducing HDL has the opposite effect, noted the researchers.
“Our message is clear, you should focus on eating a healthy, balanced, Mediterranean style diet”
Overall, they said their systematic review suggested that eating more ALA through food or supplements probably has little or no effect on cardiovascular deaths or deaths from any cause.
However, eating more ALA probably reduced the risk of heart irregularities from 3.3 to 2.6%, found the review, which is published in the Cochrane Database of Systematic Reviews.
The review team found that reductions in cardiovascular events with ALA were so small that about 1,000 people would need to increase consumption of ALA for one of them to benefit. Similar results were found for cardiovascular death.
Lead author Dr Lee Hooper, from the University of East Anglia, said: “The findings of this review go against the popular belief that long-chain omega 3 supplements, including fish oils, protect the heart.
He said the review also provided good evidence that taking long-chain omega 3, including fish oil, EPA or DHA supplements had no benefit for heart health or reducing the risk of stroke or death from any cause.
Though oily fish was a healthy food, the researchers said they were unclear if increasing intake will show beneficial effects to the heart.
“Supplements are no replacement for a healthy diet”
He added: “This systematic review did find moderate evidence that ALA, found in plant oils (such as rapeseed or canola oil) and nuts (particularly walnuts) may be slightly protective of some diseases of the heart and circulation. However, the effect is very small.”
Victoria Taylor, senior dietician at the British Heart Foundation, said: “Supplements are no replacement for a healthy diet.
“Guidance which was updated a few years ago is consistent with this study in that omega-3 supplements are not recommended to prevent heart and circulatory diseases,” she said.
“Our message is clear – rather than taking supplements to reduce your risk of having another heart attack or stroke, you should focus on eating a healthy, balanced, Mediterranean style diet,” she added.