“How much pomegranate juice should I drink?” “How many blueberries do I have to eat to get that cholesterol down?” When I get a flurry of such questions, it usually means that a report of a legitimate scientific study has appeared in the lay press, often presenting the results in an overly optimistic light.
The pomegranate craze was sparked by a couple of studies that suggested the fruit may have a role in treating breast cancer and in lowering the risk of heart disease. By the time the tabloids got through with their interpretation of the results, pomegranate juice had become the new wonder kid on the block. And, needless to say, pomegranate capsules are now featured in health-food stores as cancer-preventatives and as treatments for menopause.
But what did the researchers really find? They discovered that there are compounds in pomegranate juice that have estrogenic activity. In other words, they can alter the way that cells respond to the body’s own estrogen. This is certainly of great interest because more than two-thirds of breast cancers are estrogen positive, meaning that the body’s estrogen stimulates the proliferation of tumor cells. Any substance that reduces such estrogenic stimulation is most welcome. And it seems that some of the polyphenols in pomegranate can do just that. They block the activity of an enzyme known as “aromatase,” which is involved in the synthesis of estrogen. (Drugs known as “aroma-tase inhibitors” are now commonly prescribed in the treatment of some breast cancers.) How did the scientists determine the aromatase blocking activity of pomegranates? By studying the effect of the juice on breast cancer cells in the laboratory. They discovered that extracts of the seeds, which is what pomegranate juice really is, reduced the activity of 17-beta-estradiol, the estrogen of concern in breast cancer, by some 50 percent. And breast cancer cells that experienced this reduction in estrogen stimulation died with much greater frequency than normal cells. Of course, this is a laboratory finding, and is still a long way away from showing that pomegranate juice has any effect on actual cancers in the body. There is a big difference between bathing cultured cancer cells in pomegranate juice in a petri dish and drinking the juice. Nobody knows if the active ingredients can be absorbed from the digestive tract and if they have any chance of making it to the site of a tumor. But it seems a pretty good bet that pomegranate juice is not harmful, and may do some good.
Although its benefits for breast cancer may be iffy, pomegranate’s role as a heart disease preventative is on firmer footing. Israeli researchers investigated the effect of pomegranate juice on LDL cholesterol or, in everyday language, “bad cholesterol.” The juice reduced the conversion of LDL into its most damaging form, known as “oxidized LDL.” This finding really may be more than a laboratory curiosity. Why? Because the researchers also found that when mice specially bred to develop hardened arteries were given pomegranate juice, the size of the lesions in their arteries was reduced by 44 percent. So, basically, while the hype about pomegranate juice may not be completely justified, there is something to it. A daily glass of 8 ounces just may provide surprising benefits. When ten patients with diagnosed atherosclerosis drank a daily glass of pomegranate juice for a couple of years, their blood pressure dropped by 20 percent, and they also experienced a beneficial reduction in the thickness of their carotid artery walls. These effects were not seen in subjects who consumed a placebo drink free of flavonoids, the pigments in pomegranate juice that are believed to be responsible for desirable effects. So, drink the juice, just don’t spill any on your clothes. Pomegranate stains are virtually impossible to get out! Ditto for blueberry stains, which you may also have to deal with if you follow the research in that area.
We’ve heard before about all the good things blueberries may do for us. Anthocyanins, the pigments responsible for the distinct color of the berries, fall into a category of compounds called antioxidants, and a wealth of research suggests that these are good for us. They may discourage blood clot formation, improve night vision, slow macular degeneration, reduce the risk of cancer, and protect brain cells from aging. So far, it is this anti-aging effect that has captured the imagination of the lay press. While nobody has yet shown that humans who load up on blueberries age more slowly, there have been some intriguing rodent studies. At Tufts University in Boston, a group of elderly rats was put on a blueberry-rich diet, while another group was treated to regular laboratory food. The blueberry-treated rats improved in balance, coordination, and short-term memory.
By the time a rat is nineteen months old (equivalent to about seventy years old for a human), the time it takes them to walk a narrow rod before losing balance drops from thirteen to five seconds. But after eating blueberry extract for eight weeks, the old rats managed to keep their balance for eleven seconds! They also negotiated mazes better! This was the study that the press seized upon, and all of a sudden, blueberries were elevated to the status of a wonder food. And now, with the announcement that pterostilbene (another compound found in blueberries) may reduce cholesterol, the nutritional status of the berries has risen to even loftier heights. The truth is that the study in question was not done on humans, and not even on live animals. It was done in the laboratory, on rat liver cells. The researchers did show that pterostilbene activates a specific receptor on these cells that is linked with reducing cholesterol and triglycerides. But nobody knows if this compound, when ingested, does the same thing in a human liver, or if it even gets there. Nobody knows how many blueberries would have to be eaten to lower blood cholesterol, or indeed if they really can do this.
That doesn’t mean such research is to be ignored. My guess— hopefully an educated one—is that blueberries should, as often as possible, be a part of the five to ten servings of fruits and vegetables that experts recommend we consume every day. So I’m ready to raise a glass of pomegranate juice to the researchers who have shown that there just may be something special about blueberries.