Men who take fish oil supplements or eat fatty fish may be more likely to contract prostate cancer, an international study has found.
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The research reported a 71 per cent increased risk of prostate cancer among men who consume omega-3s, fatty acids regularly extolled for their health benefits.
Lead author Alan Kristal, of the Fred Hutchinson Cancer Research Centre in Seattle, said the study reinforced that nutritional supplements may be harmful.
Scientists cannot explain the connection, but findings indicate omega-3s are involved in the formation of tumours.
Cancer Council Australia chief executive Ian Olver said: ''The reality is that if something is good for you, it doesn't mean that 10 times of it is better. It is unlikely someone would be diagnosed with a deficiency of fish oil. There is a view out there that extra vitamins and antioxidants are good for you. And people take more thinking that more is better.''
Published in the Journal of the National Cancer Institute, the findings confirm a 2011 study that linked high blood concentrations of DHA, an anti-inflammatory fatty acid, to more than double the risk of high-grade prostate cancer. ''The findings suggest that these fatty acids are involved in prostate tumorigenesis and recommendations to increase long-chain omega-3 fatty acid intake, in particular through supplementation, should consider its potential risks,'' the study said.
Professor Peter Howe, a nutrition expert at the University of Newcastle said taking fish oil had ''shown improvements in cardiovascular health, cognitive performance in the aged and reduced inflammation''.
The Heart Foundation recommends adults consume at least 500 milligrams of omega-3 every day from oily fish or fish oil supplements. ''We don't know how much omega-3 people are getting. We should introduce a test to measure omega-3 status when we visit the GP,'' Professor Howe said.
Pros and cons of fish oil supplements
Positives
- Anti-inflammatory powers
- Lower blood pressure
- Relief of rheumatoid arthritis
- Reduced risk of diabetes
- Improved circulatory function
- Improved mood and cognitive performance
Negatives
- Increased risk of bleeding
- Rise in blood glucose levels
- Increase in LDL cholesterol
