Studies have consistently reported that extracts of apples and apple peel can inhibit the growth and proliferation of breast cancer cells, including both hormone receptor positive (ER+/PR+) and triple negative (ER-/PR-/HER2-) types, without harming normal cells. The chemopreventive effectives of apples appears to be due to their phytochemical content.
This includes fisetin, phloretin, quercetin, ursolic acid and anthocyanins (red peeled varieties only).
Phloretin has been shown to increase the cytotoxic effects of the chemotherapy drug Taxol (paclitaxel). Ursolic acid has been shown to inhibit tumor development and suppress angiogenesis (the growth of new blood vessels). Regular consumption of apples has been found to be associated with reduced breast cancer risk in population studies. Now a new study has reported that flavonoids (pigments found in a wide variety of plants) extracted from the peel of Pink Lady apples caused significantly higher levels of programmed cell death in ER+/PR+ breast cancer cells than flesh flavonoids.

Whole organic apples with red or reddish peels are best

Apples with red, red-streaked or pink peels have the highest beneficial micronutrient content, which is concentrated in their peels. However, conventionally grown apples typically are produced using relatively high levels of pesticides. Such apples normally are washed after picking, which removes some of the pesticide residue, but also strips off some of the natural apple wax (the waxy cuticle, which contains ursolic acid and other compounds) that is part of the peel. Food grade wax is then applied to the apples, which can seal in some of the remaining pesticide residue. Therefore, organic apples are best.
Consuming apple juice is less beneficial than drinking apple juice. Apple juice processing and filtering removes some of the beneficial nutrients found in apples. Commercially produced apple juice can contain significant levels of arsenic, depending on the orchard soils where the apples were grown. According to the FDA, even organic apples can come from trees grown in soil that may contain arsenic. This is because arsenic-based pesticides were commonly used in the U.S. until 1970, leaving traces that persist in some soils. However, the situation in other countries can be far worse. Unfortunately, it can be difficult to determine where the apple juice concentrate used to make juice is sourced. Asia and South America are major suppliers of apple juice concentrate used in the U.S.

Latest research finds peel has greater chemopreventive effects than flesh

The study referenced at the beginning of this news story was designed to investigate the antioxidant and anticancer effects of flavonoids from Pink Lady Apples on human colon cancer (LoVo) and hormone receptor positive breast cancer cells (MCF-7). Pink Lady peel flavonoids were found to have greater antioxidant properties than flavonoids extracted from the flesh of the apples.
Both the peel and the flesh flavonoids were found to inhibit the growth of both colon and breast cancer cells. However the peel flavonoids were more effective. Scavenging ROS (reactive oxygen species) effects were also found to be significantly higher in peel flavonoids. The authors also determined that the generation of ROS was a vital mediator in flavonoid-induced cell apoptosis (programmed cell death). Peel flavonoids caused significantly higher levels of apoptosis than flesh flavonoids.
Please see our articles on apples and how to optimize your breast cancer diet for more information.