Following recent news on the impact of exercise to cancer risk and survival, new research from Harvard T.H. Chan School of Public Health reports on the impact of dietary choices in young women on their likelihood of developing breast cancer in later life.

The reports are published online in The BMJ.

The research team, led by Maryam Farvid, research associate at Massachusetts General Hospital and visiting scientist at the Harvard T. H. Chan School of Public Health, evaluated adolescent fruit and vegetable intake and risk of breast cancer in 44 223 women, with a follow-up rate over 98% of total potential person years from 1998 through 2013.

These came from a larger survey cohort of over 90,000 participants completing the Nurses' Health Study, and in 2013 the follow up reported 3235 cases of invasive breast cancer, of whom 1347 had completed the supplementary adolescent intake survey.

Total fruit consumption during adolescence was associated with a lower risk of breast cancer, with a hazard ratio of 0.75 (95% confidence interval 0.62 to 0.90; P=0.01 for trend) for the highest (median intake 2.9 servings/day) versus the lowest (median intake 0.5 serving/day) fifth of intake. 

The association for fruit intake during adolescence was independent of adult fruit intake.

“This study underscores the importance of what a young girl eats for her future health,” says Farvid. “This study also has an important message for schools and the need to provide students with the opportunity to consume more fruits and vegetables as part of the school meal program.”

Higher early adulthood intake of fruits and vegetables rich in α carotene was associated with lower risk of pre-menopausal breast cancer. The hazard ratio was 0.82 (0.70 to 0.96) for the highest fifth (median intake 0.5 serving/day) versus the lowest fifth (median intake 0.03 serving/day) intake.

Addition of vegetables, particularly broccoli, to patient diets has been reported to improve survival outcomes and reduce risks of differing tumour types before, but Farvids' study addresses wider dietary impacts.

The association with adolescent fruit intake was stronger for both oestrogen and progesterone receptor negative cancers than oestrogen and progesterone receptor positive cancers (P=0.02 for heterogeneity).

In particular, greater consumption of apple, banana, and grapes during adolescence and oranges and kale during early adulthood was significantly associated with a reduced risk of breast cancer.

Fruit juice intake in adolescence or early adulthood was not associated with risk.

We recommend whole fruit and not fruit juice,” says Farvid, “because maybe one of the most important ways that fruit decreases risk of breast cancer is through fiber, and even natural fruit juice often has no fiber in it.”

Source: The BMJ