The team from Harvard Medical School assessed the combined impact of soy products and different types of tea on a breast cancer model in mice. Both foods have been attributed to the lower incidence of breast cancer in Asian women.
The mice were treated with genistein-rich soy isoflavones, soy phytochemical concentrate, black tea and green tea individually, and then with a soy phytochemical-black tea mixture and a soy-green tea combination.
Researchers assessed the growth of tumours and increase in cells as well as expressions of tumour oestrogen receptors.
Both the soy isoflavones and the soy phytochemical concentrate led to dose-dependent inhibition of tumour growth by slowing cancer cell proliferation, they reported in the 1 January issue of the International Journal of Cancer (vol 108, issue 1, pp 8-14).
As expected, green tea showed more potent anti-breast tumour activity than black tea. Green tea infusion at 1.5g of tealeaf per 100 ml of water produced significant reductions of 56 per cent in final tumour weight. But green tea with soy concentrate at 0.1 per cent of the diet further reduced final tumour weight by 72 per cent, they said.
"Our study suggests that dietary soy phytochemicals plus green tea may be used as a potential effective dietary regimen for inhibiting progression of oestrogen-dependent breast cancer," concluded the researchers.