Abstract
Epidemiological studies suggest that consumption of phytoestrogens, in particular isoflavones, correlates with a lower incidence of breast cancer. However, data from human intervention studies have been less clear. Several meta-analyses have reported beneficial but relatively weak effects of isoflavone consumption on reduction of hot flushes and osteoporosis and improvement of cholesterol levels. However, the effects of isoflavones on early breast cancer markers differ between pre- and post-menopausal women. Conclusions on whether exposure of animals (mice and rats) to isoflavones protects against or promotes breast cancer development and growth vary between different studies. These results, taken together with the heterogeneous outcomes of human interventions, have led to a controversy surrounding the intake of isoflavone to reduce breast cancer risk. Here, we describe the results of recent human and animal intervention studies and discuss factors that might explain the variation in results. We also describe possible molecular mechanisms of action of isoflavones; distinguishing which mechanism(s) are involved is needed if we are to solve the controversy surrounding the actions of these compounds.
Highlights
Phytoestrogens constitute a large group of naturally occurring compounds with a structural resemblance to estrogen. e two main subgroups of phytoestrogens, isoflavones and lignans, are present in foods such as soy, lentils, beans, chickpeas, whole-grain cereals, legumes and various vegetables and fruits, berries
Future outlook and conclusions epidemiological studies suggest that isoflavones can decrease both breast cancer risk and even increase survival of breast cancer patients [20,21], the intervention studies and animal experiments are not as conclusive
We can at least say that for post-menopausal women there are no serious adverse effects following the consumption of soy isoflavones for a limited period of time [22,23]
Summary
Phytoestrogens constitute a large group of naturally occurring compounds with a structural resemblance to estrogen. e two main subgroups of phytoestrogens, isoflavones and lignans, are present in foods such as soy, lentils, beans, chickpeas, whole-grain cereals, legumes and various vegetables and fruits, berries. In particular isoflavones, can have both estrogenic and antiestrogenic effects, it has been suggested that they can modulate breast cancer risk. We describe the heterogeneous results of recent human intervention studies and animal experiments on the effects of isoflavone on breast cancer risk.
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