There is no evidence of a clear benefit to health from fats which are commonly found in oily fish, researchers say.
Web URL: Read the BBC News item here
Download File: BMJ Editorial - BMJ, doi:10.1136/bmj.38798.680185.47 (published 24 March 2006) (56.22 KB)
This news item is misleading in that it appears to relate to general health, but this is not what either Dr. Lee Hooper et al's review article claims or what is stated in the British Medical Journal's editorial of 24 March. The editorial states categorically:
For the general public some omega 3 fat is good for health
and it goes on to say that:
Adequate intake of omega 3 fats is particularly important for women of childbearing age.
(BMJ, doi:10.1136/bmj.38798.680185.47, published 24 March 2006 - scroll down to end of page to download this editorial in pdf format).
The Hooper et al. review examined only cardiovascular events and cancer, mostly in men. Principally because one study - which unusually specifically enrolled men treated for angina - contradicted other previous large studies, they concluded that:
It is not clear whether long chain or short chain omega 3 fats (together or separately) reduce or increase total mortality, cardiovascular events, cancer, or strokes. The review did not look at other aspects of health.
More research is called for. We are learning about the effects of omega 3 all the time, but the general health benefits of eating oily fish and omega-3 fatty acids are not in dispute.
BBC News Article continues:
Consumption of omega-3 fatty acids is thought to protect against heart disease and UK guidelines advise eating four portions of oily fish a week.
But the British Medical Journal review of 89 earlier studies looking at heart disease, cancer or strokes found no evidence the fats offered protection.
Heart experts said people should not stop eating oily fish, such as salmon.
The balance of evidence had suggested omega-3 fats decreased mortality, but then one large-scale trial came to a contradictory conclusion - changing the overall picture.
That trial looked at the impact of omega-3 fats on patients with chronic heart disease and suggested the fatty acid did nothing to prevent a recurrence of these conditions.
Looking at 3,114 men with stable angina in 2003 it found that those given high amounts of oily fish were at a higher risk of heart attack and recorded an increased number of cardiac deaths.
The authors could not say why the results of this trial differed from other large studies in the field.
They therefore concluded that it was not clear whether omega-3 fatty acids reduced or increased total mortality, cardiovascular events, cancer and strokes.
The team led by Lee Hooper, lecturer in the school of medicine, health policy and practice at the University of East Anglia in Norwich, said: "UK guidelines encourage the general public to eat more oily fish, and higher amounts are advised after myocardial infarction (heart attacks).
"This advice should continue at present but the evidence should be reviewed regularly.
"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."
Epidemiology expert Dr Eric Brunner, of the Royal Free and University College London Medical School, said for the general public some omega-3 was good for health.
"Whether omega-3 fat prevents cognitive impairment and dementia is currently being tested in trials, with the first results expected in 2008," he said.
"It seems that for healthy people the health advice remains well-founded but for people with chronic heart disease there is now a doubt."
Dr Mike Knapton, director of prevention and care at the British Heart Foundation, said people should not stop consuming omega-3 fats or eating oily fish as a result of this study.
"Until now, medical research has demonstrated a benefit from omega 3 fats in protecting people from heart and circulatory disease," he said.
"This systematic review of numerous studies concludes that there is no clear evidence either way.
"More research is needed to establish why some studies have shown a slightly increased risk associated with eating very high amounts of oily fish, which is possibly related to mercury levels."