This article originally appeared in the February 2007 Harvard Health Letter and is provided courtesy of Harvard Health Publications.

Pomegranates for the prostate and the heart: Seeds of hope
Few American men have heard of the pomegranate, and fewer still have eaten the curious-looking fruit loaded with red seeds. But if new scientific studies bear fruit, this exotic edible may one day find a place in healthful diets.
What are pomegranates?

Pomegranates are exotic in America but commonplace in the Middle East. They are the fruit of the Punica granatum tree, which is native to Iran and is also cultivated in some Mediterranean countries and in parts of Russia, Afghanistan, India, China, and Japan.
Pomegranates are relatively new to Americans, but they have a venerable history. Legend holds that they grew in the Garden of Eden, and they have a place in the mythology and traditions of ancient Greece, Persia, Babylonia, and China.

The edible portion of a pomegranate is composed of 80% fruit and 20% seeds. Like other foods, the pomegranate contains hundreds of chemicals. Unlike many other foods, though, some of the pomegranate’s chemicals have strong biological actions and potential medical benefits. The fruit is 85% water and 10% sugar — but it also contains large amounts of vitamin C and a variety of polyphenols and tannins, which have potent antioxidant activities. The seeds contain fiber, a steroid estrogen, estrone, and isoflavones, including two (genistein and daidzein) that are abundant in soy. The seeds also contain a unique oil that contains an uncommon fatty acid, punicic acid.

Chemistry in action
Historians have traced the role of the pomegranate in ancient civilizations, anthropologists have documented its use in folk medicine, and chemists have described its complex constituents. Medical scientists have gone one step further by showing that pomegranate extracts and juices have potentially important biological activities.

Pomegranate extracts can slow the multiplication of and promote the death of cancer cells by apoptosis, a phenomenon that’s been characterized as cell suicide. Laboratory studies also reveal that pomegranate components can retard angiogenesis, the process that supplies tumors with the new blood vessels that they need to grow. The cancer cells that have been studied most extensively come from breast and prostate tumors. Flavonoids present in green tea and soy have similar antitumor activities.

Pomegranate extracts also have actions that may protect the heart and blood vessels. As potent antioxidants, they can protect cholesterol from the oxidative damage that allows it to damage the walls of blood vessels. Pomegranates also have anti-inflammatory properties that may reduce the inflammation that characterizes the progression of atherosclerosis. Antiplatelet actions of the juice could also help prevent artery-blocking blood clots. Many of these properties of pomegranates are also displayed by red wine, which is rich in similar polyphenols.

Pomegranates and the prostate
Test-tube experiments suggest that pomegranate juices and extracts may help fight prostate cancer. Two studies, one in mice and the other in men, hint that these laboratory effects may have clinical relevance.

Scientists at the University of Wisconsin grew cells from highly aggressive cases of human prostate cancer in tissue culture. They discovered that pomegranate fruit extracts slowed the growth of cancer cells and promoted cell death by apoptosis. The next step was new and even more significant. The researchers implanted the human prostate cancer cells in three groups of specially prepared mice. One group received plain drinking water while the other groups’ water was laced with low or higher doses of pomegranate juice extract. The pomegranate-treated mice developed significantly smaller tumors than the untreated animals, and they also had lower blood PSA levels. Moreover, the higher dose of pomegranate fruit extract worked better than the lower dose.

Mice are not men, but a small, preliminary study suggests that pomegranate juice may have clinical activity in humans. The volunteers were 46 patients who had rising PSA levels after surgery or radiation treatment for early prostate cancer. The men were clinically well and did not require conventional therapy. Doctors tracked each man for at least six months without any treatment, monitoring PSA levels and calculating the PSA doubling time, a measure of tumor growth rate. During the next phase, each patient drank 8 ounces of commercially available pomegranate juice every day while PSA monitoring continued. The calculated average PSA doubling time increased from 15 months before treatment to 54 months on pomegranate juice. Blood samples taken during pomegranate treatment were also more active against prostate cancer cells grown in test tubes than samples obtained before treatment.

Pomegranates and the heart
Preliminary results in test tubes, animals, and humans suggest that pomegranates may have beneficial effects on cardiovascular disease. Studies in mice and men show that drinking pomegranate juice can protect LDL (“bad”) cholesterol from oxidative damage. In addition, pomegranate juice slows the progression of plaques in mice with atherosclerosis.

Two small clinical studies are even more intriguing. Doctors in Israel studied 19 patients with atherosclerotic narrowing of their carotid arteries. All the volunteers received the best conventional medical treatments; 10 also received a daily dose of pomegranate juice. After a year, the carotid artery thickness had increased by 9% in the conventionally treated patients but had decreased in the pomegranate group. Blood pressure also fell significantly during pomegranate treatment; no side effects were reported.

The Israeli study was not a randomized trial, but a 2005 American study randomly assigned 45 patients with coronary artery disease to receive pomegranate juice or a placebo in addition to their normal clinical care. Stress tests with nuclear scans were performed at the start of the study and after three months; the patients who drank 8 ounces of commercially available pomegranate juice a day enjoyed improved cardiac blood flow.

Pomegranates? Perhaps
Pomegranate juice is commercially available in the United States and is being promoted for health as well as flavor. Early studies raise hopes that pomegranates may have clinical benefits for prostate cancer and heart disease, but much more research is needed before we’ll know if these hopes are justified. Meanwhile, men who enjoy the ruby red color and tart flavor of pomegranate juice can drink up. Remember, though, that the juice is expensive and contains 140 calories in a serving. Preliminary research also suggests that pomegranate juice may share grapefruit juice’s potential interaction with certain medications. And a 2006 report implicated pomegranate juice in a case of statin-induced muscle damage.

In ancient times, the Persians believed pomegranates could protect them in battle, the Babylonians regarded the fruit as an agent of resurrection, and the Chinese used it to symbolize longevity. In the future, doctors may classify the pomegranate as a functional food with medicinal benefit. Without denying that potential, though, men should still think of the pomegranate as an interesting fruit that can be made into a tasty juice with a striking red color.