London – Teenage girls are being encouraged to eat five portions of fruit and vegetables a day to cut their risk of developing breast cancer.
Researchers say the daily intake of fibre can cut the risk by as much as a quarter. And the earlier girls start eating healthy foods packed with dietary fibre, the more they are protected.
Harvard School of Public Health scientists analysed data from more than 90 000 women over a 25-year period. For each additional 10g of daily fibre intake – for example an apple, two slices of whole wheat bread or half a cup each of cooked kidney beans and cooked cauliflower or squash – during early adulthood, the risk dropped by more than an eighth (13 percent).
Depending on how much dietary fibre they ate in early adulthood, the risk was reduced from between 12 and 19 percent. But eating lots of fibre as a teenager was associated with a 16 percent lower risk of overall breast cancer and a 24 percent lower risk of breast cancer before menopause.
Researcher Maryam Farvid said: “Previous studies of fibre intake and breast cancer have almost all been non-significant, and none of them examined diet during adolescence or early adulthood, a period when breast cancer risk factors appear to be particularly important.
“This work on the role of nutrition in early life and breast cancer incidence suggests one of the very few potentially modifiable risk factors for pre-menopausal breast cancer.”
Dr Walter Willett added: “From many other studies we know that breast tissue is particularly influenced by carcinogens and anticarcinogens during childhood and adolescence. We now have evidence that what we feed our children during this period of life is also an important factor in future cancer risk.”
The scientists said the greatest apparent benefit came from fruit and vegetable fibre and was one simple lifestyle choice women could take to reduce breast cancer risk before the menopause.
The study suggested eating more fibre-rich foods may lessen breast cancer risk partly by helping to reduce high oestrogen levels in the blood, which are strongly linked with the cancer development.
Breast cancer is the most common type of cancer in the UK and a fifth of those diagnosed with the disease are under 50. In 2011, just under 50 000 women were diagnosed with invasive breast cancer.
The study, published in the journal Pediatrics, analysed 90 534 women who participated in the Nurses’ Health Study II, a long-running investigation of factors that influence women’s health.
A spokesperson said: “Fruit and vegetables are a good source of vitamins and minerals, including folate, vitamin C and potassium.
“They’re an excellent source of dietary fibre, which helps to maintain a healthy gut and prevent constipation and other digestion problems. A diet high in fibre can also reduce your risk of bowel cancer, and help to reduce your risk of heart disease, stroke and some cancers.”