Brussels, 29 Mar 2006
A new British study has questioned the much-hyped benefits of consuming omega-3 fatty acids. The research identified 15,159 studies, of 89 were considered sufficiently robust. While the use of omega-3 may not be detrimental to health, the team found that 'Omega 3 fats do not have a clear effect on total mortality, combined cardiovascular events, or cancer.'
Omega-3 oils are considered to be essential for human health, but cannot be manufactured in the human body, and must be consumed. Omega-3 oils have been implicated in some high-profile health claims. Many of these claims have dubious scientific origin. For example, omega-3's role in mental function is highly controversial. However, benefits for cardiac health had been generally accepted. This new study, published in the British Medical Journal, has questioned those health benefits.
In recent years, the use of fish oils, particularly oils rich in omega-3, has been associated with a myriad of health benefits, from improvements in cardiac function to increased memory or even intelligence. The pan-UK team led by Professor Lee Hooper from the University of East Anglia conducted a meta-analysis of omega-3 studies.
The study found that the effects of omega-3 are contradictory. Most studies found a negligible or slightly positive effect. However, one study, the diet and angina randomized trial (DART) in 1989, found that there was, if anything, a slightly damaging effect for omega-3.
In fact, the DART study found that the number of sudden cardiac deaths was highest in a group taking extra omega-3 in capsule form, but 'omega 3 from oily fish has a different effect to fish oil supplements, but this was investigated by Burr et al [the DART study] and found not to explain the differences', leaving the root cause of this anomaly mysterious.
The researchers believe that it may be important to make distinctions between types of cardiac disease, for instance between those patients with angina, and those who suffer acute myocardial infarction (heart attack). Their conclusion was that there is 'no strong evidence that omega 3 fats protect against cardiovascular events', but that, 'It is probably not appropriate to recommend a high intake of omega 3 fats for people who have angina but have not had a myocardial infarction.' The team also 'found no evidence that omega 3 fats had an effect on the incidence of cancer.'
The initial problem for the team was to wade through the large variance in studies - how the omega-3 was administered, in what quantities, and which types. Eventually, they concluded that: 'Our findings do not rule out an important effect of omega 3 fats on total mortality, as robust trials at low risk of bias reported few deaths. There is no evidence that the source (dietary or supplemental) and dose of omega 3 fats affected the effectiveness of long chain omega 3 fats.'
A possible reason for the detrimental effects of omega-3 in one study could be down to levels of pollutants in fish. Fish stocks are declining, and the pollutants, such as mercury and dioxin-like chemicals contained within the fish, are increasing. Long-term exposure to the pollutants in fish may outweigh the benefits of omega-3. The only way to separate the two is to make further studies into the effects of omega-3 and fish on health.
Alternative sources of omega-3 fatty acids, such as from krill, will soon be commercially available. Scientists in the US have recently developed GM pigs that develop their own omega-3. 'We could use these animals as a model to see what happens to heart health if we increase the omega-3 levels in the body,' said Dr Randy Prather from the University of Pittsburgh.
The EU has funded a number of projects on omega-3 fatty acids, including a study of the Production of omega 3 fatty acids and applications in the food industry, and a project on omega-3 in hen eggs.