An excellent source of amino acids, iron, calcium and other micronutrients, soy products are a versatile ingredient with many health benefits. Especially tofu, it is safe for women diagnosed with breast cancer, and may even prolong their survival, a new study has found.
Soy foods are considered among the healthiest for human consumption, but their oestrogen-like properties have raised concerns about a potential increased risk of breast cancer. This is because in hormone receptor-positive cancer, the most common form of the disease, there are some concerns that high oestrogen levels help cancer cells grow and spread, though this remains controversial.
‘Isoflavones – the component of soy that has oestrogen-like properties – have been shown to slow the growth of breast cancer cells in laboratory studies,’ said Fang Fang Zhang, from the Tufts University in the US.
To provide some clarity, researchers looked at the relationship between dietary intake of isoflavones and death from any cause in 6235 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 percent lower risk of dying than women who consumed low amounts.
This decrease was largely confined to women with hormone receptor-negative tumors and women who were not treated with anti-oestrogen therapy such as tamoxifen (which blocks the effects of oestrogen).
In contrast to some previous research, high levels of isoflavone intake were not associated with greater mortality among women receiving hormonal therapy.
‘Based on our results, we do not see a detrimental effect of soy food intake among women who were treated with endocrine therapy,’ said Zhang.
More than 20 percent of all new breast cancer cases with known oestrogen and progesterone receptor status are receptor-negative, and they have poorer survival rates than hormone receptor-positive cases.