Fish oil data significant rather than dramatic
Analysis: Online study not entirely new
Before you give up eating oily fish or reduce your intake of omega -3 supplements it is worth looking at the research in more detail.
The headlines announcing a 71 per cent increased risk of high-grade prostate cancer in men with high levels of fatty acids derived from fish oils are both dramatic and attention- grabbing.
But before you give up eating oily fish or reduce your intake of omega -3 supplements it is worth looking at the research in more detail.
The online study, published in the Journal of the National Cancer Institute, is not an entirely new piece of research; rather it is a reworking of data originally collected as part of a selenium and vitamin E cancer-prevention trial.
This trial was designed to see if selenium or vitamin E, either alone or combined, reduced prostate cancer risk. It showed no benefit from selenium intake and an increase in prostate cancers in men who took vitamin E.
In the latest analysis, US researchers focused on 834 men who had been diagnosed with primary prostate cancers (156 had high-grade cancer) along with a comparison group of 1,393 men aged over 50 selected randomly from the 35,500 participants in the trial. High-grade cancers are tumours that are more likely to spread aggressively and to be fatal.
Their findings follow previous research that found a link between high blood concentrations of a single omega-3 fatty acid and a doubling of the risk for developing high-grade prostate cancer.
What is surprising about the recent studies is that they fly in the face of the known anti-
inflammatory properties of omega-3 fatty acids.
We know that inflammation plays a role in the growth of some cancers.
But cancer is a highly complex disease with its genesis only partly understood, so the next challenge is to identify what exactly is happening to fatty acids in the body to turn them into substances that damage cells.
An important aspect of any new research is to look beyond percentages. The original trial results from 2011 show that after 5½ years on vitamin E supplements there were 17 per cent more cases of prostate cancer in men taking vitamin E compared with men given a dummy pill.
In absolute terms this translates into an additional 11 cancers per 1,000 men studied – statistically significant but perhaps not as dramatic as the percentages might suggest.
What are the implications of the latest research? It does not suggest that people who follow a recommended diet of fish should change their eating habits. Older men who take omega-3 supplements have a choice: reduce intake now or wait for more research.