Until now, though, no comprehensive study has conclusively proved the claims.
Now co-ordinators of the largest-ever survey on breast cancer hope to provide the definitive guide on which foods to avoid, what to eat to help keep the disease at bay – and which lifestyle factors will increase your risk of developing the disease.
Evidence already suggests that using dietary measures alone can cut the risk of breast cancer by as much as half. Soya, fruit and vegetables are thought to help reduce the risk. In addition, studies show that pregnancy and breast-feeding tend to protect against the disease, although women on the Pill and HRT are shown to have an increased risk.
Researchers conducting the new survey, funded by the European Commission, will question thousands of women with breast cancer below the age of 40 from seven different countries including Scotland.
Those quizzed will be asked about their diet before and after breast cancer, the use of hormonal pills, the amount of exercise taken each week, the number of children they have and the age at which they gave birth. The women will also be asked about their family history of the disease.
Scientists have already discovered that two mutations in a gene are responsible for 70 per cent of breast cancer cases where the disease runs strongly in the family. The genes called BRCA1 and BRCA2 contain errors in their make-up which can reduce the body’s ability to fight cancer. It is also thought that other mutations known as BRCA3 influenced by environmental factors can contribute to developing the disease.
The researchers will divide those taking part into three main groups: those women with BRCA1 and BRCA2 mutations, BRCA3 mutations and those with no genetic risk factors.
The survey, which forms part of a longer-term study will take three years.
Evidence so far suggests that pregnancy tends to protect against breast cancer, probably by reducing a woman’s lifetime exposure to oestrogen. Women who do not have children are 10 to 30 per cent more likely to develop the disease.
It’s also thought that breast-feeding may help prevent the disease. Women who have breast-fed for at least two years in total are thought to enjoy a 20 per cent to 30 per cent reduction in risk.
Studies also show that women who take the Pill are up to twice as likely to develop breast cancer, depending on length of use. Other research suggests that women who take HRT for five years or more have a 35 per cent increase in risk.
There is also evidence linking a diet high in fruit and vegetables with a reduced risk of breast cancer. Fruits and vegetables tend to be high in antioxidant nutrients such as betacarotene and vitamin C, and these help to combat damaging molecules called free radicals, which are heavily implicated in the processes that cause cancer.
Other research shows that soya can also help reduce breast cancer risk. Populations, such as the Japanese, who eat an abundance of such foods have been shown to enjoy significantly reduced rates of the disease. However, researchers found that Japanese girls who moved to America have a much higher risk of breast cancer than their contempories who stayed in Japan. This implies diet plays an important part in protecting against cancer.
The research team taking part in the latest survey also hopes to explain why a higher incidence of breast cancer occurs in Scotland. Statistics show that one in nine women develop breast cancer in Britain as a whole – but the incidence in Scotland is slightly higher. More than 13,000 women die from breast cancer each year – and Britain has the highest death rate in the world.
‘I would be very surprised if certain foods in the Scottish diet are not responsible for some incidences of breast cancer,’ says Professor Steel.
‘If we can identify the foods and lifestyle changes that protect against breast cancer, we hope to half the Scottish incidence of breast cancer. However, this would depend on people willing to change their habits quite radically.’
Article Credit: Daily Mail