Fish oil health benefits not clear, says new study

London: A new study by the published online by the British Medical Journal today doesn’t find evidence of a clear benefit of omega 3 fats on health.

These findings do not rule out an important effect of omega 3 fats, but suggest that the evidence should be reviewed regularly, say the researchers.

Consumption of long chain omega 3 fatty acids, found in oily fish and fish oils, and a shorter chain omega 3, found in some plant oils, is thought to protect against heart disease. UK guidelines encourage the general public to eat more oily fish, and higher amounts are advised after a heart attack.

Researchers analysed 89 studies (48 randomised controlled trials and 41 cohort studies) to assess the health effects of long and short chain omega 3 fats on total mortality, cardiovascular events, cancer, and strokes.

Each study involved a treatment group and a control group and investigated the effect of omega 3 intake on health for at least six months. Differences in study quality were taken into account to identify and minimise bias.

Pooling the results showed no strong evidence that omega 3 fats have an effect on total mortality or combined cardiovascular events. The few studies at low risk of bias were more consistent, but they also showed no effect of omega 3 on total mortality or cardiovascular events.

When data on long chain omega 3 fats were analysed separately, total mortality and cardiovascular events were not reduced. No study showed increased risk of cancer or stroke with higher intake of omega 3, but there were too few events to rule out important effects.

Other recent reviews of omega 3 trials found that omega 3 fats decrease mortality, but the publication of a large contradictory trial has changed the overall picture. The authors cannot say exactly why the results of this trial differ from the other large studies in this field.

They therefore conclude 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.

UK guidelines advising people to eat more oily fish should continue at present but the evidence should be reviewed regularly, say the authors. However, it is probably not appropriate to recommend a high intake of omega 3 fats for people who have angina but have not had a heart attack.

To understand the effects of omega 3 fats on health, we need more high quality randomised controlled trials of long duration that also report the associated harms, they conclude.

We are faced with a paradox, says Eric Brunner in an accompanying editorial. Health recommendations advise increased consumption of oily fish and fish oils. However, industrial fishing has depleted the world’s fish stocks by some 90% since 1950, and rising fish prices reduce affordability particularly for people with low incomes.

Global production trends suggest that, although fish farming is expanding rapidly, we probably do not have a sustainable supply of long chain omega 3 fats, he warns.

Oily fish may prevent spread of prostate cancer

Manchester: Including oily fish, containing Omega 3 fatty acids may prevent the spread of prostate cancer to other parts of the border, according to research by the Paterson Institute for Cancer Research at the Christie Hospital.

Prostate cancer is the most common cancer among men and is particularly dangerous if it infects areas such as bone marrow.

Omega 3 fats, found in mackerel, fresh tuna, salmon and sardines, have already been found to cut the risk of contracting the cancer. And this research suggests they might prevent a more aggressive form of the disease developing particularly when Omega 3 is combined with Omega 6 oils.

The experts looked at prostate cells in the laboratory and examined the extent to which they spread to bone marrow.

Both types of oils are essential for good health, but a balance could be required as omega 6 was found to help cancer to spread.

Dr Mick Brown, chief scientist in the research group, said that Omega 6 fats, found in vegetable oils, nuts and seeds, increased the spread of tumour cells into bone marrow. And this was blocked by Omega 3, so a balance was required.

The findings, published in the British Journal of Cancer, may also help in the development of drugs to stop other cancers, such as breast cancer, from spreading in the body.

Other research shows that a daily dose of fish oils could help keep Alzheimer’s disease at bay.

A team from St Bartholomew’s Hospital in London looked at the effect of omega 3 supplements on the number of glutamate receptors in the brains of aging rats. These are known to be essential to memory and alertness.

After 12 weeks, the researchers found that the concentration of glutamate receptors in the brains of rats who ate unsupplemented food had decreased. But the animals whose food had been enriched had as many as much younger rats, the journal Neurobiology of Aging reports.

The researchers believe the same could hold true for humans and say that omega 3 could hold promise as a treatment for Alzheimer’s disease.