Diet rich in fish may reduce the spread of prostate cancer

Eating foods such as fish that are rich in omega 3 fats might help prevent the spread of prostate cancer to other parts of the body, according to research published in the British Journal of Cancer* today (Tuesday 21 March 2006).

Prostate cancer is the most common male cancer in the UK. Men face a much more dangerous form of the disease if tumour cells from the prostate gland migrate and invade other parts of the body such as bone marrow. However, researchers funded by the Association for International Cancer Research (AICR) and the Medical Research Council (MRC), and based at the Paterson Institute at the Christie Hospital in Manchester, have found that an omega 3 fat can inhibit invasion by prostate cancer cells in laboratory tests, which may reduce their ability to spread to secondary sites.

Omega 3 fats are found in so-called ‘oily’ fish such as salmon, mackerel and fresh tuna. It has previously been claimed that they have protective effects against cancer. This research, though still at an early stage, suggests that a diet rich in particular omega 3 fats might protect men with prostate cancer from developing a more aggressive form of the disease.

There are two main groups of polyunsaturated fatty acids found in our diet – omega 3 and omega 6. Both types have essential roles in keeping us healthy but the Manchester research shows they have very different effects on prostate cancer cells.

Dr Mick Brown from the Paterson Institute, chief scientist in the research group, said: “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.”

Mr Noel Clarke, consultant urologist at the Christie Hospital and 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 where it may be monitored safely or more easily treated with surgery or radiotherapy.”

The Food Standards Agency recommends men can eat up to four portions** of oily fish a week.

Derek Napier, chief executive of the AICR, said: “Understanding what drives prostate cancer cells to invade the bone marrow might enable the development of ways to interfere with that process. We know that many forms of the disease, including breast and prostate cancer, seem to invade bone marrow rather than other parts of the body. If it could be shown that this is influenced by the proportion of different types of fat, then we might be able to develop drugs that limit the movement of cancer cells.”

Professor John Toy, medical director of Cancer Research UK, which owns the British Journal of Cancer, said: “Diet is a factor in many types of cancer, but its potential role is not yet fully clear in prostate cancer. 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.

“Cancer Research UK advises people to reduce their risk of cancer by eating a healthy diet, high in fibre, fruit and vegetables and low in red and processed meat.”

ENDS

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