SCIENTISTS say they have found the first “unequivocal evidence” that eating oily fish could help reduce the risk of breast cancer.
• Tests on mice points to benefit of omega-3
The researchers discovered that a life-long diet rich in omega-3 fatty acids, found in foods such as oily fish like salmon and vegetable oils, could cut the growth of tumours by 30 per cent.
While studies have shown that omega-3 can help reduce the risk of heart disease, there has been conflicting evidence linking it to beneficial effects in cancer.
But the latest research, published in the Journal of Nutritional Biochemistry, produced what scientists said was believed to be the first “unequivocal evidence that omega-3s reduce cancer risk”.
Health campaigners said more research was needed to investigate how diet affects cancer risks.
For the latest study, the team from the University of Guelph in Ontario created “transgenic mice” - genetically altered to naturally produce omega-3 fatty acids in their bodies and also to develop aggressive mammary tumours.
These mice were then compared to mice who were only genetically engineered to develop tumours.
The researchers found that the mice who produced omega-3 developed only two-thirds as many tumours as the other mice.
The tumours suffered by these mice were also 30 per cent smaller compared to the mice without omega-3 in their systems.
Professor David Ma, from the university’s Department of Human Health and Nutritional Sciences, said: “The difference can be solely attributed to the presence of omega-3s in the transgenic mice - that’s significant.
“The fact that a food nutrient can have a significant effect on tumour development and growth is remarkable and has considerable implications in breast cancer prevention.”
Breast cancer affects around 4,500 women in Scotland every year, with 1,000 deaths annually.
An increased risk of developing the disease has been linked to genetics and hormones in the body, as well as lifestyle factors such as alcohol, smoking and diet.
Prof Ma said their own findings on the potential impact of diet on breast cancer were significant.
“We show that lifelong exposure to omega-3s has a beneficial role in disease prevention – in this case, breast cancer prevention,” he said.
“What’s important is that we have proven that omega-3s are the driving force and not something else.”
Many experts have long believed that diet may significantly help in preventing cancer.
But Prof Ma said that epidemiological and experimental studies to back up these claims had been lacking, and human studies were inconsistent.
“There are inherent challenges in conducting and measuring diet in such studies, and it has hindered our ability to firmly establish linkages between dietary nutrients and cancer risk,” he said.
“So we’ve used modern genetic tools to address a classic nutritional question.”
Prof Ma said he hoped that the study would lead to more research on using diet to reduce the risks of cancer.
“Prevention is an area of growing importance,” he said.
“We are working to build a better planet, and that includes better lifestyle and diet.
“The long-term consequences of reducing disease incidence can have a tremendous effect on the health-care system.”
James Jopling, director for Scotland at Breakthrough Breast Cancer, said: “It is difficult to pin-point which dietary factors are important when it comes to breast cancer as we all eat a variety of different foods and our diet changes over time.
“It’s important to remember this experiment was done on mice and not humans.
“Much more work is needed before we’ll know how exactly diet influences breast cancer risk.
“What we do know is that nearly 4,500 women are diagnosed with breast cancer in Scotland each year. We also know that women can reduce their risk of developing this disease by limiting their alcohol consumption, getting physically active and maintaining a healthy weight.”