New research indicates that dietary soy products are safe and even beneficial for women diagnosed with breast cancer. Published online in the journal Cancer , the findings may help resolve the long-running debate surrounding soy’s potential link to breast cancer outcomes as a result of its oestrogen-like properties.
Isoflavones, the component of soy with oestrogen-like properties, have been shown to slow the growth of breast cancer cells in laboratory studies, and epidemiological analyses in women with breast cancer found links between higher isoflavone intake and reduced mortality. However, other research has suggested that the isoflavones may reduce the effectiveness of hormone therapies for breast cancer.
The new study examined the relationship between dietary intake of isoflavones and death from any cause in 6,235 American and Canadian women diagnosed with breast cancer. Over a median follow-up of nine years, women with breast cancer who consumed high amounts of isoflavones had a 21 per cent lower risk of dying than women who consumed low amounts. This decrease was largely confined to women with hormone receptor-negative tumours and women who were not treated with anti-oestrogen therapy. In contrast to some previous research, high isoflavone intake was not associated with greater mortality among women receiving hormonal therapy.