While it is widely believed that high fruit and vegetable consumption reduces cancer breast cancer risk, population studies generally have found only weak effects or no effect. On the other, numerous fruits and vegetables have been found to be associated with reduced breast cancer risk when examined individually. In fact, the type of plant-based food matters. When it comes to breast cancer prevention, apples are more effective than pears and black beans are more effective than peas. The chemopreventive effects of plant foods appears to be due, in part, to their flavonoid content. Now a new meta-analysis of previous studies has determined which types of flavonoids are most associated with reduced breast cancer risk.

Flavonoid supplements are not recommended

There is some evidence that the impact of flavonoids on breast cancer cells depends on the dosage, with low or high doses potentially stimulating breast cancer cell growth in some cases. When flavonoids are consumed as part of food, they are combined with other micronutrients that have been shown to act synergistically against breast cancer. Consuming flavonoid-rich foods is safe. On the other hand, safe and effective dosages of flavonoid supplements have not been established and such supplementation has the potential to increase breast cancer risk and reduce the effectiveness of treatment.

Latest research finds link between flavonols and flavones and reduced risk

The study referenced at the beginning of this news story was designed to investigate the associations between various types of flavonoids and risk of breast cancer. To conduct the study, the authors selected relevant prospective or case-control studies published before July 1st, 2012 for analysis. A total of 12 studies incorporating 9,513 breast cancer cases and 181,906 cancer-free controls were included. There were six prospective studies and six case-control studies. The authors then calculated summary risks of breast cancer for the highest compared to the lowest consumption levels of each flavonoid subclass.

Women with high intakes of flavones were found to have a 17% lower risk of breast cancer than those with low intakes. Similarly, women with high intakes of flavonols had a 12% lower risk of breast cancer. While a slight reduction in breast cancer risk was observed for high intakes of flavan-3-ols (7%), flavanones (5%), anthocyanins (3%), and total flavonoids (2%), these results were not statistically significant.

Analysis of the three case-control studies that took menopausal status into account suggested that flavonols, flavones and flavan-3-ols intakes are associated with a significant reductions in breast cancer risk in postmenopausal, but not premenopausal, women. The authors conclude that intake of flavonols and flavones is associated with lowered breast cancer risk, especially among postmenopausal women.

Please see our article on how to optimize your breast cancer diet for more information on how to make beneficial food choices.