Eating fruit as a teenager protects against breast cancer decades later

Eating a lot of fruit during adolescence can lower your risk of breast cancer by a quarter, according to a study published in the British Medical Journal.

The results suggest that this is the period when breast tissue is most vulnerable to carcinogens.

During the study, researchers from the University of Oxford followed the diets of 90,000 nurses for over 20 years, half of whom could recall their usual diet during adolescence.

They found that high fruit consumption during teenage years (which they defined as three portions a day) was associated with a 25 per cent lower risk of breast cancer among women by the time they had reached menopause.

There is a particular association between reduced risk and consumption of apples, bananas and grapes. But the researchers say there is no evidence of a link between fruit juice consumption and breast cancer rates.

In an editorial linked to the study, the researchers said: ‘Much more evidence is needed before we can draw conclusions on the reported protective association between adolescent fruit intake and breast cancer risk. But these foods have well known beneficial effects on health, and efforts should continue to increase intake of both fruit and vegetables at all ages.’

The authors warn that the study is observational rather than biological, and that other factors could be playing a part in the results.

Instant analysis
So, the results: a higher pre-adulthood intake of fruit and vegetables was associated with reduced risk of postmenopausal breast cancer; higher consumption of fruit and vegetables in adulthood, however, did not seem to affect the cancer risk.

It is an interesting finding. We should remember that correlation, and not causation, is established by this study. Recall bias is among the factors that may have skewed the results.

Having said that, we do have other evidence rendering this correlation biologically plausible. Higher fruit and vegetable intake is associated with lower rates of obesity too, itself a strong risk factor for cancer.

The majority of breast cancer is sporadic and not due to genetic factors (eg BRCA mutations) and is also postmenopausal; these findings are thus potentially applicable to a large number of women.

Recent evidence suggests that lifestyle factors play an important role in cancer development. Women and men should be encouraged at all ages to adopt a lifestyle that is as healthy as possible, making regular consumption of fruit and vegetables a cornerstone of that lifestyle.
TSA
Research score: 4/5