Over half a million news cases of prostate cancer are diagnosed every year world wide, and the cancer is the direct cause of over 200,000 deaths. More worryingly, the incidence of the disease is increasing with a rise of 1.7 per cent over 15 years.
The new study, published on-line in the British Journal of Cancer (doi: 10.1038/sj.bjc.6603030), reports the effects of omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and the omega-6 fatty acid, arachidonic acid (AA), on the spread of human prostate cancer cell lines.
The researchers found that a metabolite of AA, prostaglandin E2, helped the spread of the prostate cancer cells to bone marrow cells.
However, when EPA and DHA were present at just half the concentration of the omega-6 fatty acid, this spread of cancer cells was stopped.
"Omega 6 fats, found in vegetable oils, nuts and seeds, increased the spread of tumour cells into bone marrow. This invasion was blocked by omega 3 fats - the ones found in oily fish. It is possible to have a healthy balance of these two types of fat - we only need about half as much omega 3 as omega 6 - that will still stop cancer cells from spreading," said lead author Mick Brown from the Paterson Institute.
Noel Clarke, principal investigator of the research group, said: "We think tumours may exploit the omega 6 fats as a high energy source - giving them the energy they need to maintain a high growth rate - and to create important signalling molecules.
Omega 3 fats are known to interfere with the various functions of omega 6 fats, something confirmed by our findings. This effectively removes the cancer's 'free lunch', a fact that may have clinical importance.
Some tumours develop slowly in the prostate without producing symptoms and sometimes when symptoms do develop, it is because the cancer has already spread. Eating a diet with the right balance of omega 3 and omega 6 fats may well help to keep prostate cancer within the prostate gland."
Professor John Toy, medical director of Cancer Research UK said that the study showed that diet is a factor in many types of cancer, but stressed that its potential role in prostate cancer was not clear.
"This research shows an effect in the laboratory. However, we would need large population studies to provide the needed evidence to say a change in diet could reduce prostate cancer cells from spreading," said Toy.
The risk of pollutants from oily fish, such a methyl mercury, dioxins, and polychlorinated biphenols (PCBs) have led to some to claim to reduce fresh fish intake, especially for pregnant women who may damage the development of their babies.
Such advice has seen the number of omega-3 enriched or fortified products on the market increase. Most extracted fish oil are molecularly distilled and steam deodorised to remove contaminants.
The European omega-3 market was worth around €160m (£108m) in 2004, say Frost and Sullivan, and is expected to grow at rates of 8 per cent on average to 2010.
According to Mintel's Global New Products Database (GNPD) the launch of omega-3-containing product across Europe has increased from 153 in 2004 to 208 in 2005. 2006 has seen 72 launches so far.