Soya limits the effectiveness of breast cancer treatment

February 1, 2017

Women advised not to start consuming soya following a breast cancer diagnosis
Tamoxifen is commonly prescribed to help women overcome the disease
But soya’s active compound, genistein, affects the the drug’s impact, experts say
However, women who historically ingested soya prior to a diagnosis are safe

James Draper For Mailonline

Published:
09:45 EST, 1 February 2017

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Updated:
14:12 EST, 1 February 2017

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It is considered a healthy alternative to dairy milk – and is famously popular among the yummy mummy crowd.

But experts warn that women shouldn’t start consuming soya milk after a breast cancer diagnosis – because it may limit the effectiveness of treatment.

Tamoxifen could be inhibited due to soya’s active compound, genistein, interfering with the medicine’s action, a study found.

Paradoxically, the naturally-occurring ingredient remains safe for women if it formed part of their diet before diagnosis, scientists claim.

Soya’s active compound, genistein, interferes with the actions of drugs used to treat breast cancer, scientists have found

Professor Leena Hilakivi-Clarke, of Georgetown Lombardi Comprehensive Cancer Centre, who conducted the biological pathway on rats, explained that timing of genistein intake is crucial.

‘Oestrogen drives most breast cancer growth, yet high soya intake among women in Asian countries has been linked to a breast cancer rate that is five times lower than Western women, who eat much less soya,’ she said.

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‘We have solved the puzzle in our rat model. See, while many oncologists advise their patients not to take isoflavone supplements or consume soya foods, our findings suggest a more nuanced message.

‘Our results suggest that breast cancer patients should continue consuming soya foods after diagnosis, but not to start them if they have not consumed genistein previously.’

Women shouldn’t start consuming soya milk after a breast cancer diagnosis – because it may limit the effectiveness of treatment, experts warn

The study, which was published in the journal Clinical Cancer Research, could help patients improve the role that diet plays on their treatment.

Lead researcher Dr Xiyuan Zhang added that longtime sustained use of genistein before a diagnosis has a similar action to Tamoxifen.

‘It inhibits a mechanism called autophagy that would allow cancer cells to survive, which explains why it helps tamoxifen works,’ she said.

However, starting to consume it after breast cancer develops not trigger anti-tumour immune response to eliminate cancer cells when tested on rats.

Those consuming genistein as adults had a 7 per cent chance of breast cancer recurrence after tamoxifen treatment, compared with a 33 per cent recurrence with rats exposed to genistein only after breast cancer developed.

Dr Zhang added: ‘We do not know yet why this made the animals resistant to the beneficial effects of tamoxifen and increased risk of cancer recurrence.’