Yesterday’s food scare du jour was all about grapefruit, and how it apparently increases the risk of breast cancer in post-menopausal women.
As ever, we were pressed into service to comment on this to the media. Here are some points of interest:
- It’s quite a big study – a 50,000 woman cohort is something you can’t really dismiss out of hand.
- Although there were a large number of women involved in this study, ‘only’ about 1,600 developed breast cancer, which makes the statistical analysis a little harder, and the conclusions much less certain.
- Grapefruit has been show to interfere with the metabolism of several drugs.
- It’s been shown to interfere with oestrogen metabolism.
- Since oestrogen metabolism is known to affect breast cancer risk, its a fair hypothesis that grapefruit might affect breast cancer risk, and this study was designed to answer this question.
- The study relied on questionnaires, i.e. it asked women how much grapefruit they remembered eating, as opposed to following women over a period of years and actually measuring how much they ate. Questionnaire-based studies are much less reliable than ‘forward-looking’, prospective studies.
- No study has ever before shown a link between grapefruit and breast cancer risk.
- One study (albeit a very small one, on rats) suggested that grapefruit might contain compounds that actually protect against cancer.
- So, in conclusion, the jury’s still out.
That’s not to say there’s no link – the theory the study set out to test is based on sound, valid science; and we know that there’s something in grapefruit juice that can potently affect our metabolism.
However, given that we DO know a lot about breast cancer risk in general – and that we think we know why its on the increase in Western society (basically, women having fewer children later and being overweight after the menopause) – its safe to say that it’s highly likely that if grapefruit plays any role at all in the trends we’re seeing in breast cancer rates, it’s a very very small one.
And remember – eating five portions of fruit and vegetables, every day, is a great way to reduce your risk of many types of cancer.