Blueberries (Vaccinium corymbosum) rank among the highest of all fruits and vegetables in their capacity to destroy free radicals. Blueberries have been shown to have neuroprotective, cardioprotective and cholesterol-lowering properties. Blueberries are a rich source of anthocyanins, including various delphinidins, malvidins, petunidins, cyanidins and peonidins. Blueberries also contain resveratrol, pterostilbene, catechin, epicatechin, kaempferol, myricetin, quercetin, p-coumaric acid, p-hydroxybenzoic acid, chlorogenic acid, gallic acid, and ursolic acid, all of which have been reported to have anti-cancer properties.
Breast cancer-related effects of eating blueberries
Blueberries have been found to inhibit mammary cancer cell proliferation in mice and rats, as well as inhibiting cultured cancer cell growth in the laboratory and blood vessel tumors in rats. Pterostilbene has been shown to inhibit obesity-related breast cancer growth and proliferation in the laboratory and to have additive treatment effects when combined with tamoxifen in estrogen receptor positive (ER+) breast cancer cells. Pterostilbene also has been shown to reduce the formation of breast cancer stem cells and inhibit their metastatic activities.
Blueberries are a good source of resveratrol, which has been shown to increase the effects of radiation treatment, aromatase inhibitors and the chemotherapy drugs Adriamycin (doxorubicin) and Taxol (paclitaxel) against breast cancer. Delphinidin, an anthocyanin found in blueberries, has been shown to block epidermal growth factor receptor (EGFR) signaling in breast cancer cells (EGFR is expressed at high levels in at least 30% of breast cancers and is associated with a poor prognosis). Delphinidin was shown to induce apoptosis (programmed cell death) in HER2+ breast cancer cells in another study.
Ursolic acid has been shown to reverse multidrug resistance in breast cancer cells. One study reported that ursolic acid resensitized multidrug resistant ER+/PR+ breast cancer cells to Adriamycin chemotherapy.
Blueberry extract has been shown to exhibit antitumor activity against triple negative (ER-/PR-/HER2-) breast cancer cells and reduce their metastatic potential. Blueberry was found to inhibit cell proliferation in triple negative cells with no effect on normal breast cells in one study. Blueberry also reduced the metastatic potential of triple negative cells through inhibition of cell motility.
In animal studies, dietary blueberry has been shown to reduce triple negative tumor volume in female mice. Blueberry diets reduced triple negative proliferation (as measured by Ki-67) and increased cell death. In addition, a blueberry diet inhibited triple negative tumor metastasis in another mouse study. Analysis of tumor tissues has demonstrated that blueberry-fed mice tumors have significantly altered expression of genes important to inflammation, cancer, and metastasis.
While frozen blueberries have lower vitamin C content than fresh berries, freezing does not appear to significantly reduce blueberry anthocyanin levels.
The antioxidant properties of blueberries have been shown to be reduced when eaten with milk, suggesting that the best way to gain maximum benefits from blueberries and other fruits eaten for their polyphenol content is to consume them either one hour before or two hours after protein is consumed.
Non-organic blueberries must be washed very thoroughly to remove pesticide residue as much as possible.
Bilberries, which grow wild in much of northern Europe, are closely related to blueberries. They are valued for their high flavonoid content. Bilberry extract has been shown to induce programmed cell death in hormone receptor positive (ER+/PR+) breast cancer cells.
Below are links to recent studies concerning this food. For a more complete list of studies, please click on blueberries.