Researchers at the Harvard Medical School say that for every portion of chips eaten per week in the pre-school years, the risk of breast cancer is increased. The data comes from a long-running study into the health of 80,000 nurses who have been followed for decades by a team from the research institute. The Nurses’ Health Study has already produced many links between diet and disease, some disproved by further and better research.

The latest paper, in the International Journal of Cancer, used data from 582 women with breast cancer and 1,569 women without the disease in 1993.

The researchers looked at the diets of the women when they were aged between 3 and 5, using information from their mothers, who were asked how often their daughters ate or drank various products.

The risk of getting breast cancer by the age of 60 is about one in 25. Karin Michels and colleagues estimated that eating chips just once a week before the age of 5 would raise that to about one in 20 — an increase in risk of 27 per cent.

The team said that while eating potatoes was not associated with increased risk, the preparation of French fries — frying in fat high in saturated fats and trans-fatty acids — may be of relevance.

Dr Michels said: “Researchers are finding more evidence that diet early in life could play a role in the development of diseases in women later in life. This study provides additional evidence that breast cancer may originate during the early phases of a woman’s life and that eating habits during that phase may be particularly important.”

She said that their data should be interpreted with caution because information on diet was dependent on the mother’s ability to recall her daughter’s diet.

“Mothers were asked to recall their daughter’s pre-school diet after the participants’ breast cancer status was known, and it is possible that mothers of women with breast cancer recalled their daughter’s diet differently than mothers of healthy women. Other foods perceived as less healthy, such as hot dogs or ice-cream, however, were not associated with breast cancer risk.”

Pamela Goldberg, the chief executive of Breast Cancer Campaign UK, said: “Studies looking into how nutrition in early life might affect the risk of developing breast cancer are very interesting. In this case we need to take into account that the study relies solely on mothers recalling what their daughters ate 40 or 50 years ago.

“We would encourage women of all ages to eat a healthy, well-balanced diet with plenty of fruit and vegetables.”

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