For years, health professionals have urged Australians to make sure they’re getting enough omega-3 fats in their diet.
And many consumers have done as they were told. Fish oil is our most-commonly taken supplement - even ahead of multivitamins, according to Australian Bureau of Statistics data.
We may have been wasting our money - at least when it comes to heart disease.
A major review by global volunteer network of medical experts Cochrane released on Wednesday, has found strong evidence they do nothing to reduce our risk of cardiovascular events, coronary heart deaths, coronary heart disease events, stroke or heart irregularities.
Other large studies have reported similar findings but the Cochrane review is important because scientists consider its evidence – compiled from 79 randomised trials involving 112,059 people and carefully checked to be free of bias – to be the gold standard.
“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,” said Dr Lee Hooper, the review’s lead author. “We don’t see protective effects.”
Scientists searching for a way to reduce the West’s huge heart-disease burden once had high hopes for omega-3s. These fats play an important role in building the membranes of our cells, and in early studies seemed to reduce cholesterol and cut inflammation.
Studies on the Greenland Inuit people in the 1970s seemed to show very few of them suffered from heart disease – which researchers believed was linked to diets high in fatty fish. Japanese and Koreans, who also have high levels of fish in their diets, were later shown to enjoy similar benefits.
This information, coupled with a range of other studies hinting at benefits from supplementation, has led to a number of highly reputable health organisations getting behind a high-fish diet – and fish oil supplements for those who don’t eat enough.
The American Heart Association recommends supplements, for example. Australia's Heart Foundation recommends two to three serves of oily fish a week for heart health - and supplements as a "good option" for people who do not eat enough fish.
But there is now enough evidence to show that eating fish oil is very different to eating fish – although it’s not clear fish is heart-healthy either.
“Despite our best hopes and a sound scientific basis for a benefit of omega-3 fats in the diet, researchers have been unable to demonstrate a clear clinical benefit in heart disease,” Professor Robert Gibson, a leading Australian fatty-acid researcher at the South Australian Health and Medical Research Institute, told Fairfax Media.
A huge number of studies have now been done that examine long-term fish oil supplementation, many of them comparing it to a placebo. By combining these studies, Dr Hooper’s team was able to develop a database of high-quality evidence.
The results were underwhelming, to say the least. Increased omega-3 intake via supplements had “little or no effect on all-cause deaths and cardiovascular effects,” the study said. Supplementation “probably makes little or no difference to cardiovascular death, coronary deaths or events, stroke, or heart irregularities”.
Earlier studies that seemed to show a strong benefit had a greater risk of bias, the authors noted.
There are fewer studies looking at the effect of a high-fish diet on heart health, so the evidence is not as high-quality. But here too the results underwhelm.
“While oily fish is a healthy food, it is unclear from the small number of trials whether eating more oily fish is protective of our hearts,” said Dr Hooper, a researcher at the University of East Anglia.
Consumers who just take supplements miss out on all the other benefits of eating fish, which is a rich source of nutrients.
However, this is unlikely to be the last word on fish oil supplements. “Similar systematic reviews of omega-3 fats in pregnancy have demonstrated a clear effect on increasing gestation and prevention of early pre-term birth. So omega-3 fats do have a role to play in human health,” said Professor Gibson.
Carl Gibson, chief executive of Complementary Medicines Australia, which represents fish oil manufacturers, said there was plenty of evidence "not to be ignored" showing fish oil was heart healthy.
"There is a large pool of research not to be ignored which provides evidence that omega-3 fatty acids are effective in lowering the incidence of coronary heart disease, stroke and heart attack, especially amongst those who have survived a heart attack and those with high blood cholesterol," he said.
Over the years Cochrane has conducted several reviews on taking omega-3 pills for other conditions. The results for these conditions have also been disappointing:
- Bipolar disorder and depression: not enough evidence
- Dementia: moderate-to-high quality evidence concluding no effect
- Age-related macular degeneration: moderate-to-high quality evidence concluding no effect
- ADHD in children: low-quality evidence concluding no effect
- Childhood allergies: not enough evidence