Mar 26 2006
In a turn up for the books, experts are now saying that contrary to the widely held belief that the omega 3 fats found in oily fish help prevent heart disease, this has not been proven.
What is more, U.S. experts agree with the findings of this latest British study.
Omega-3 fats are a type of polyunsaturated fat which have long been thought to be beneficial for health; as the body cannot make its own omega-3 fats, they must be taken in through the diet, or in supplement form.
A diet rich in omega 3 fats has to date been accredited with - decreasing the risk of irregular heart rhythms (arrhythmias), which can lead to sudden cardiac death and decreasing the levels of triglyceride - a type of fat found in the blood which has been linked to heart disease; reducing the clumping together of small particles in the blood called platelets which can cause potentially harmful clots and lowering blood pressure.
Other research has also suggested that omega-3 fats can cut the risk of such cancers as prostate and skin, improves behaviour in violent and antisocial teenagers and have been touted as a treatment for asthma and inflamed bowels.
Other research has suggested that a lack of omega-3s during foetal development can hinder brain and eye development and studies are currently testing the possibility that the fats could prevent memory loss and dementia.
The report reviewed the findings of 89 studies aimed at assessing the effects of omega 3 consumption from fish or supplements on total mortality, heart problems, strokes and cancer.
The researchers at the University of East Anglia in Norwich, say that people without heart disease will suffer no harm from consuming fish, and quite possibly could do themselves some good.
They also say there is proof that omega 3 consumption may help people who have already had heart attacks or other cardiac problems.
Lead author of the report Lee Hooper, a lecturer in research synthesis and nutrition at the University says the end picture is a mixed one with two major studies showing a benefit, but the most recent large study did not.
Hooper says they found no clear evidence that they are of any use at all and say the findings suggest the fats did nothing to prevent a recurrence of chronic heart conditions.
They actually found that men with angina given high amounts of oily fish were at a greater risk of heart attack.
Hooper says one problem in interpreting the findings is that most of the trials included people who already had cardiac problems such as heart attacks or angina.
She says more, and larger trials are needed to determine the true preventive benefits of omega 3 consumption.
An expert panel in June 2004 of the U.S. National Heart, Lung, and Blood Institute came to much the same conclusion and said additional studies were needed before recommendations could be made to the general public.
Dr. Eliseo Guallar, associate professor of epidemiology and medicine at the Johns Hopkins Bloomberg School of Public Health, and a member of the panel has said such studies are expensive and the results would take up to seven years to reach any conclusions.
Guallar says the value of omega 3 in fish oil for people with existing heart problems is not questioned and a study has shown that people who suffered heart attacks substantially reduced their risk of sudden death by taking 850 milligrams of fish oil a day.
He recommends eating at least two fish meals each week.
The heart association also recommends consumption of plants such as soybeans, canola and flaxseed, which contain a different version of omega 3 oils, although some experts are not convinced that the omega 3 in plants have the same benefits as those in fish.
The Food Standards Agency recommends that people eat oily fish regularly - but no more than four portions a week.
Mackerel, lake trout, herring, sardines, albacore tuna and salmon are good sources of omega 3.
It also recommends that women who are pregnant, breastfeeding, or planning to have children in the future should limit their intake to a maximum of two portions a week due to concerns that some fish may be contaminated with pollutants such as mercury, dioxins and PCBs (polychlorinated biphenyls).
High levels of dioxins and PCBs can affect the development of an unborn baby.
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