A new study published by the influential Cochrane Library concludes that there is little or no effect of omega 3 supplements on the risk of experiencing heart disease, stroke or death. But some experts say that trial criteria applied by the Cochrane researchers produced findings of limited validity, while benefits of fish oils observed in the study were downplayed by the authors.
Cochrane researchers specifically wanted to examine evidence for “the widely held view” that taking omega-3 supplements reduces risk of heart disease, stroke and death.
Their review examined 79 earlier randomised c0ntrolled trials (RCTs) involving over 112,000 people which had assessed effects of greater omega-3 intake versus lower or no omega-3 intake for heart and circulatory disease. Most of the trials used omega-3 fats in supplement form.
The researchers found that increasing EPA and DHA (the omega-3 fats found in fish) has little or no effect on all-cause deaths and cardiovascular events and probably makes little or no difference to cardiovascular death, coronary deaths or events, stroke, or heart irregularities. They reported that “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”.
Lee Hooper, of the University of East Anglia, who led the study, told The Times: “We can be confident in the findings of this review which go against the popular belief that long-chain omega-3 supplements protect the heart. However, she said that advice to include regular portions of oil fish in the diet should remain. “The difference between eating oily fish and taking supplements is that it’s not just the omega-3 you’re getting. you’re also getting a protein source that replaces something else in your diet like saturated fat, and seafood has selenium, iron and vitamin D. All of these are useful nutrients.”
The researchers do acknowledge that criteria they used to decide which evidence to include in their study, and which to leave out, influenced overall findings with the result that “effect sizes moved closer to no effect for all primary outcomes except arrhythmias“.
Several experts have already commented on the study’s design limitations. Tom Sanders, PhD, professor emeritus of Nutrition and Dietetics, King’s College London, said: “The major limitation of this review of randomised controlled trials is that it has been unable to allow for the increased intakes of omega-3 fatty acids over the past 20 years.”
“Most of the trials in this review were in patients with pre-existing cardiovascular disease (CVD), which is a further limitation when extrapolating to the prevention of heart attacks in the general population. This is important as a substantial proportion of first heart attacks are fatal (it is worth noting that this proportion has fallen greatly in the past twenty years). Previous observational cohort studies, not looked at here, suggest that omega-3 fatty acids may reduce the risk of sudden cardiac death,” he added.
Harry Rice, PhD, vice president of scientific and regulatory affairs for the Global Organization for EPA and DHA Omega-3s (GOED), told nutraingredients.com: “While the authors should be applauded for the breadth of their review, their overall interpretation of the data demonstrated a lack of appreciation for and understanding of the decades of research demonstrating the heart health benefits of omega-3s. Such research includes not just meta-analyses, but RCTs, observational studies, as well as animal and in vitro studies. It’s about the totality of the scientific evidence.”
The nutritionist and health writer Patrick Holford, told Natural Products Global: “This is not a study to determine if taking omega-3 fish oil supplements to those at risk of heart disease, or older people, might help prevent a heart attack. It was a statistical conglomeration of any study that involved people aged 18 or over either given an omega-3 supplement, or fish, or simply given dietary advice to eat fish. Every nutritional therapist knows to give 1,000mg of omega-3 in fish oil to those at risk – and eat oily fish three times a week. Very few people in these studies were given this.
“Almost everything improved – less cardiovascular disease risk, less stroke risk, but little effect on actual cardiovascular deaths. The length of studies were, in the most part, under a year and very few were ‘at risk’. In the worst case scenario an 18 year old takes part in a study and is advised to eat fish once a week. One year later they are still alive. Is that hardly surprising?
“Any drug that could do this would be a best-seller”
“To quote the researchers summarising the effects of all these studies combined omega-3 “probably slightly reduces risk of coronary heart disease events [by 13%] and cardiovascular disease events [by 11%], may slightly reduce risk of coronary heart disease death and having a stroke [by 9%].” Omega-3 lowered cholesterol, triglycerides (fat) and weight. Any drug that could do this would be a best-seller. How on earth this then warrants headlines such as of omega-3 benefits being “nonsense” beggars belief. I can only imagine that omega-3 fish oils are becoming more popular and threatening the market for relatively ineffective, expensive and often harmful drugs.”