Pomegranates are a very good source of important chemopreventive polyphenols, including ellagic acid, punicic acid, gallic acid, ursolic acid, delphinidin, and cyanidin-3-O-glucoside. Pomegranate seeds also are a source of the lignan enterolactone. Pomegranates have been shown to suppress inflammation and joint damage in rheumatoid arthritis, improve bone health, reduce hypertension and heart disease, reduce cholesterol, protect against UVB-induced damage to human skin, protect the brain, and improve sperm quality in rats. In addition, pomegranates have 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
Pomegranates and pomegranate extracts have been shown to inhibit breast cancer cell proliferation and invasion and promote cell apoptosis in both estrogen receptor positive (ER+) and negative ER- breast cancer cells in a dose dependent manner, as well as preventing mammary tumor formation in HER2/neu transgenic mice.
Postmenopausal women with breast cancer and a high intake of enterolactone (found in pomegranate seeds) have been found to be less likely to die from their breast cancer than those with a low intake. Enterolactone has also been found to increase the sensitivity of breast cancer cells to radiation, thereby potentially enhancing the treatment effects of radiotherapy.
Delphinidin, an anthocyanin found in pomegranates, has 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.)
Pomegranate seed oil, fermented pomegranate juice polyphenols, and ellagic acid have all been shown to inhibit angiogenesis (the growth of new blood vessels) in breast cancer cells. Pomegranate fermented juice polyphenols and pomegranate seed oil have also been shown to reduce the number of carcinogen-induced mammary tumors in mice. In addition, pomegranate extract has been shown to inhibit aromatase activity, a process by which androgens are converted to estrogens in the body.
Pomegranate juice has been shown to inhibit metastatic processes in breast cancer cells. 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.
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 medication.
Selecting pomegranate juice
A pomegranate seed consists of a thin casing surrounding a juicy pulp (which together form the seed oat) containing an edible seed. 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 purple 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 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 for 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 suggesting that beets and beet juice should be consumed separately from other red vegetables and fruits and their juices, including pomegranate juice.
Pomegranate/ellagic acid formulations
The chemopreventive actions of pomegranates and pomegranate juice depends in part on synergy among the various pomegranate compounds. As noted above, pomegranates contain such beneficial micronutrients as delphinidin, cyaniding-3-O-glucoside, ursolic acid, and punicic acid 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 extract have not been confirmed.
Below are links to recent studies concerning this food. For a more complete list, including less recent studies, please click on pomegranates.