Pomegranates (Punica granatum) and pomegranate juice are a very good source of important chemopreventive compounds, including several anthocyanins, ellagic acid and the omega-5 fatty acid punicic acid. Pomegranates are also a source of gallic acid and ursolic acid. In addition, pomegranate seeds inforporate the lignan enterolactone.
Pomegranates have been shown to have strong anti-inflammatory properties. In addition, pomegranates have been reported to reduce joint damage in rheumatoid arthritis, reduce hypertension and heart disease, reduce cholesterol, protect against UVB-induced damage to skin, protect the brain, improve bone health, and improve sperm quality in rats. Pomegranates have also been shown to inhibit prostate cancer growth in mice, retard pancreatic cancer cell growth, and inhibit the proliferation of human oral, colon and lung cancer cells.

Breast cancer-related effects of eating pomegranates

Cell studies

Pomegranate and pomegranate extracts have been reported to inhibit breast cancer cell proliferation and invasion and promote cell apoptosis (programmed cell death) in both estrogen receptor positive (ER+) and negative (ER-) breast cancer cells in a dose dependent manner.
Pomegranate extract has also been shown to inhibit aromatase activity (a process by which androgens are converted to estrogens in the body), thereby decreasing estrogen production. This is important for reducing growth-stimulatory effects in estrogen-dependent (ER+) breast cancer.
In addition, pomegranate juice has been reported to inhibit metastatic processes in breast cancer cells. Pomegranate seed oil, fermented pomegranate juice polyphenols, and ellagic acid all have been shown to inhibit angiogenesis (the growth of new blood vessels) in breast cancer cells. Angiogenesis is a crucial step that separates preinvasive and dormant forms of cancer from invasive and metastatic malignant growth.

Animal studies

Pomegranate fermented juice polyphenols and pomegranate seed oil have been reported to reduce the number of carcinogen-induced mammary tumors in mice. Punicic acid, the main fatty acid found in pomegranate seeds, has been shown to inhibit both ER+ and triple negative (ER-/PR-/HER2-) breast cancer cell proliferation.
Pomegranate extract has also been demonstrated to prevent mammary tumor formation in HER2+ transgenic mice.

Pomegranate anthocyanins

Pomegranates are a rich source of a variety of anthocyanins, most importantly cyanidin and delphinidin, as well as some pelargonidin. These are closely-related plant pigments with chemopreventive properties that give the fruit its rich color. Women in the highest quartile (fourth) of anthocyanin intake had significantly lower breast cancer risk than those in the lowest quartile in one study. Anthocyanins have also been demonstrated to reduce Adriamycin (doxorubicin) chemotherapy-induced heart damage.
Cyanidins such as the cyanidin-3-glucoside found in pomegranates have been reported to suppress angiogenesis and inhibit 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.
Delphinidin has been demonstrated to inhibit carcinogen-induced transformation of normal cells into breast cancer cells. Delphinidin has also been shown to block epidermal growth factor receptor (EGFR) signaling in breast cancer cells. (EGFR, which is expressed at high levels in at least 30% of breast cancers, is associated with a poor prognosis.) Delphinidin has also been reported to suppress the growth of ER+/PR+, HER2+, and triple negative 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.
Pelargonidin is not well studied with respect to breast cancer. However, pelargonidin has been shown inhibit the growth of ER+/PR+ breast cancer cells.

Ellagic acid

Pomegranate compound ellagic acid has been shown to reduce proliferation of ER+/PR+ breast cancer cells. Ellagic acid has also been found to be effective in the prevention of estrogen-induced mammary tumors in rats. In fact, ellagic acid has been shown to inhibit breast cancer development in a variety of cell and animal studies, in part by inhibiting angiogenesis.
Both pomegranate juice and the combination of luteolin, ellagic acid and punicic acid stimulated the expression of genes that increase breast cancer cell adhesion, as well as inhibiting genes that stimulate cell migration and inhibit breast cancer cells movement to the bone, in one study. In addition, the treatments reduced pro-inflammatory compounds, which implies that they could reduce inflammation and its promotion of cancer progression.

Additional comments

Earlier studies suggested that, like grapefruit juice, pomegranate juice could affect the metabolism of certain drugs. However, it has since been demonstrated that pomegranate juice does not generally interfere with oral or intravenous anti-cancer medication.

Selecting pomegranate juice

In common parlance, a pomegranate seed consists of a thin casing surrounding a juicy pulp (the aril), which contains an edible white or light pink seed. Such "pomegranate seeds" are commonly used as an addition to salads and salsas. However, they can be challenging to extract whole from the white, spongy membrane surrounding them. Pomegranates are also relatively expensive and not available year round. Therefore, pomegranate juice is the most common form of consumption.
Most people find unsweetened pomegranate juice very bitter or sour. This problem is solved by the addition of sugar or other sweeteners or combining pomegranate with sweeter juices such as grape or blueberry juice. Of the two alternatives, juice mixtures are more healthful, but consumers must read labels carefully to avoid inferior products. For example, a quick search turned up juice (produced by a well-known national food company) with the name "100% Juice, Pomegranate Blueberry " which had apple juice as the first (and therefore, main) ingredient on the label.
In addition, juice mixtures that combine pomegranate with beet juice should be avoided. The deep red color of beets is due to betalain pigments (betanin and ibetanin) rather than the anthocyanin pigments found in pomegranates and most other red or purple fruits and vegetables. The evidence regarding whether betalain pigments are chemopreventive with respect to breast cancer is inconclusive. The problem is that combining anthocyanins and betanin neutralizes the potential anti-cancer activities of both types of pigment in breast cancer cells, according to one study. This suggests that beets and beet juice should be consumed separately from other red vegetables and fruits and their juices, including pomegranate juice.

Pomegranate/ellagic acid supplements

The chemopreventive actions of pomegranates and pomegranate juice depends in part on synergy among the various pomegranate compounds. As noted above, pomegranates contain other beneficial micronutrients such as anthocyanins in addition to ellagic acid. Pomegranate extracts with heavy concentrations of ellagitannins or ellagic acid are likely to be less effective than formulations that are simple concentrations of the fruit, according to one researcher. In addition, the safety and efficacy of pomegranate seed oil and pomegranate extracts have not been established.

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 pomegranates.