Currants are small sour berries that are normally consumed as juice, jam, or in dried form in the U.S. Black currants (Ribes nigrum), red currents (Ribes rubrum), and white currants (a cultivar of the red currant) are the most common varieties. Red currants are good sources of resveratrol and vitamin C.
Black currants have less resveratrol and vitamin C than red currants, but are an excellent source of delphinidin, a very good source of catechin, cyanidin-3-glucoside, myricetin, and quercetin, and contain some rutin, all of which have been reported to have anticancer properties. Currant roots and seeds are also high in gamma-linolenic acid (GLA), which has been traditionally used to treat pre-menstrual syndrome and other "female" health problems.

Breast cancer-related effects of eating currants

Berry consumption is associated with reduced breast cancer risk. Currants, which are related to gooseberries (Ribes uva-crispa), are a source of a variety of compounds with anti-cancer activities, including micronutrients that have been shown to increase the beneficial effects of breast cancer treatment. The few population studies that have been undertaken which have included currants have not attempted to isolate the effects of this berry.

Black currant anthocyanins

Black currants are a rich source of a variety of anthocyanins — closely-related plant pigments with chemopreventive properties that give the berries their rich color. Women in the highest quartile (fourth) of anthocyanin intake had significantly lower risk of breast cancer than those in the lowest quartile in one study. Anthocyanins have also been demonstrated to reduce Adriamycin-induced heart damage.
Delphinidin
Delphinidin has been demonstrated to inhibit carcinogen-induced transformation of normal cells into breast cancer cells. Delphinidin has also been reported to suppress the growth of hormone receptor positive (ER+/PR+), HER2 overexpressing (HER2+), and triple negative (ER-/PR-/HER2-) breast cancer cells. In addition, delphinidin has been found to inhibit the angiogenesis and migration of triple negative breast cancer cells and to reduce tumor growth in a mouse model of triple negative breast cancer.
Cyandin-3-glucoside
Cyanidins such as cyanidin-3-glucoside have been reported to suppress angiogenesis by inhibiting tumor cell proliferation and migration. Cyandin-3-glucoside has been shown to reduce HER2+ cell proliferation and interfere with the viability and metastatic potential of triple negative breast cancer cells. Cyandin-3-glucoside has also been shown to enhance the treatment effects of Herceptin in HER2+ breast cancer cells.

Myricetin

Myricetin has been shown to trigger apoptosis in ER+/PR+ breast cancer cells. Myricetin has also been demonstrated to inhibit triple negative breast cancer cell migration, invasion, and adhesion. Myricetin also reduced tumor growth and metastasis in a mouse model of triple negative breast cancer.
In addition, myricetin has been shown to increase the oral bioavailability of Taxotere (docetaxel) in rats and to enhance the cytotoxic treatment effects of Taxol (paclitaxel) in ovarian cancer cells.

Quercetin

Black and red currant flavonol quercetin has been shown to increase the effectiveness of both Adriamycin (doxorubicin) and Taxol (paclitaxel) chemotherapy in multidrug resistant ER+/PR+ breast cancer cells, in part by eliminating cancer stem cells. In addition, quercetin has been reported to increase the sensitivity of ER+/PR+ cells to 5-fluorouracil (5-FU), thereby increasing its treatment effects. Quercetin has also been found to inhibit the migration and adhesion of triple negative (ER-/PR-/HER2-) breast cancer cells and to significantly inhibit tumor progression in a mouse model of triple negative breast cancer. Finally, quercetin also acts as an iron chelator, which can help reduce iron's breast cancer-promoting effects in some women.

Resveratrol

Red currants are a very good source of resveratrol, which has been shown to increase the cytotoxic effects of radiation treatment and the chemotherapy drugs Adriamycin and Taxol against breast cancer. Resveratrol also can inhibit aromatase (the synthesis of estrogen from androgens within the body), which is important for reducing growth-stimulatory effects in estrogen-dependent (ER+) breast cancer. In fact, resveratrol has been shown to strengthen the treatment effects of aromatase inhibitors.
Resveratrol has also been reported to inhibit lung metastasis in a mouse model of triple negative breast cancer. In addition, resveratrol has been demonstrated to help protect against cisplatin-induced ovarian and uterine damage.

Black currant seed oil

Black currant seed oil, evening primrose oil, and borage oil are all commercial sources of GLA (γ-linolenic acid). GLA is an omega-6 unsaturated fatty acid with anti-inflammatory properties (unlike the omega-6 fatty acids in vegetable oils, which tend to be pro-inflammatory). GLA and its metabolites affect the expression of various genes, including ones that play a significant role in immune functions and cell death.
Low GLA levels in the fatty portion of breast tissue has been found to be associated with inflammatory breast cancer (IBC). On the other hand, one study reported that high circulating GLA was associated with increased likelihood of benign breast disease and breast cancer.
GLA has been found to increase the cytotoxic effects of Taxol and Taxotere in ER+/PR+ and triple negative breast cancer cells. GLA has also been demonstrated to reduce Adriamycin-induced cardiotoxicity. In addition, GLA has been reported to increase the treatment effects of tamoxifen in ER+ cells and to reduce HER2/neu expression.

Additional comments

Consumers should be aware that, like cranberry juice, currant juice may have high levels of sugar or other sweeteners. Approximately 20% to 50% of the berry's anthocyanin content is lost during the processing and storage of black currant juice.
Currants and currant products should be purchased organic.

Sources of information in this webpage

The information above, which is updated continually as new research becomes available, has been developed based solely on the results of academic studies. Clicking on any of the underlined terms will take you to its tag or webpage, which contain more extensive information.
Below are links to 20 recent studies concerning this food and its components. For a more complete list, including less recent studies, please click on currants.