The Mediterranean diet is a largely plant-based diet. It involves eating plenty of vegetables, fruit, beans, pulses, olive oil and oily fish. It is also characterised by a low intake of red meat and processed foods.
It has been frequently linked to better heart health, weight management, healthier brains and living longer, although any association with the risk of cancer is less well understood.
The latest study, based on 62,573 women aged between 55 and 69, found that those who stuck to a Mediterranean diet most closely could significantly reduce their risk of developing the oestrogen-receptor negative (ER-negative) subtype of breast cancer.
The findings could be particularly valuable as women with this form of cancer cannot be treated with hormone therapy and usually have a worse outcome than those with other types of breast cancer.
20-years of data
All the women were involved in a long-term health study in The Netherlands. At the outset, they completed an 11-page questionnaire detailing their diets, exercise regime, smoking habits and other factors that could influence their chances of developing cancer.
The data yielded information over a 20-year period.
During this time, there were 3,354 breast cancer cases among those taking part. However, 1,033 cases were not included in the analysis because they either had a history of cancer or their diet history wasn't complete.
The traditional Mediterranean diet often includes a moderate intake of alcohol. However, the researchers excluded alcohol from their analysis because it is a known risk factor for breast cancer.
The research, led by Maastricht University, concluded that if everybody ate a diet with the highest adherence to Mediterranean ingredients, 32.4% of ER-negative breast cancer cases and 2.3% of all breast cancers could be avoided.
The researchers say the benefits of a Mediterranean diet on reducing the risk of cancer may be explained by its high amounts of fibre, antioxidants and vitamins and its ability to reduce inflammation and oxidative stress.
The study, in the International Journal of Cancer, was funded by the World Cancer Research Fund.
An 'intriguing' study
Breast Cancer Care described the findings as "intriguing". Emma Pennery, the charity's clinical director, said in an emailed statement: "Breast cancer isn’t just one disease – not all types have the same triggers and this study unpicks these complexities."
She continues: "We know how devastating a diagnosis is and this study adds to evidence that a healthy diet, full of 'good' low-saturated fats, plays a part in lowering risk of the disease.
"However, it’s important to remember while lifestyle choices like eating a well-balanced diet and taking regular exercise can help reduce the risk of cancer, they don’t guarantee prevention. So, it's crucial women know the signs and symptoms of breast cancer, and contact their GP with any concerns."
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