Eating lots of fish, olive oil and walnuts while limiting chips, biscuits and mayonnaise can slow the growth of early prostate cancer, according to a study.

New research suggests that simple dietary changes may help reduce prostate cancer cell growth in patients undergoing active surveillance.

This is a treatment approach that involves regular monitoring of the cancer without immediate intervention.

The findings show that a diet low in omega-6 but high in omega-3 fatty acids, combined with fish oil supplements, significantly reduced the growth rate of prostate cancer cells in men with early-stage disease.

And it could extend the time before more aggressive treatment is needed, the scientists said.

Many men with low-risk prostate cancer choose active surveillance over immediate treatment.

However, within five years, about half eventually need to undergo therapy with either surgery or radiation.

Because of this, patients are eager to find ways to delay the need for treatment, including through dietary changes or supplements.

 Researchers conducted a trial involving 100 men with low risk or favourable intermediate risk of prostate cancer who chose active surveillance.

Participants were randomly assigned to either continue their normal diet or follow a low omega-6, high omega-3 diet, supplemented with fish oil, for one year.

This group were given advice on healthier, lower fat alternatives for high fat or high calorie foods, such as using olive oil or lemon and vinegar for salad dressing and trying to eat more fish and nuts.

They were also advised to reduce their intake of food with higher omega-6 content such as chips, biscuits, mayonnaise and other fried or processed foods.

These participants were also given fish oil capsules to further boost their omega-3 intake, while the other group did not receive any dietary counselling or take fish oil tablets.

The researchers tracked changes in a biomarker called the Ki-67 index, which indicates how fast cancer cells are multiplying—a key predictor of cancer progression, metastasis and survival.

Analysis showed that after one year, the low omega-6, omega-3 rich diet and fish oil group had a 15 per cent decrease in the Ki-67 index, while the control group saw a 24 per cent increase.

Dr William Aronson, Professor of Urology at UCLA and first author of the study, said: ‘This is an important step toward understanding how diet can potentially influence prostate cancer outcomes.

‘Many men are interested in lifestyle changes, including diet, to help manage their cancer and prevent the progression of their disease.

‘Our findings suggest that something as simple as adjusting your diet could potentially slow cancer growth and extend the time before more aggressive interventions are needed.’

While the results are promising, the researchers did not find any differences in other cancer growth markers which are commonly used to track prostate cancer progression.

The findings were published in the Journal of Clinical Oncology.