Pomegranates Put to the Test for Prostate Cancer

The pomegranate “has been revered through the ages for its medicinal properties”––so much so that it’s been used as a symbol for some medical organizations. A fruit seems to me a better representation of health than the American Medical Association’s snake on a stick.

The pomegranate is thought to be beneficial for a wide range of diseases, including several types of cancer, cardiovascular disease, and rheumatoid arthritis. Evidently even the cannibals love it as it improves the color of “kid meat.” The researchers were talking about baby goats, but the title of their study did make me do a double-take!

Most of the attention over the last decade has focused on pomegranates and prostate cancer. In vitro studies have shown that pomegranate extract can suppress the growth of prostate cancer cells in a petri dish by up to 95 percent. As you can see in my video Pomegranate vs. Placebo for Prostate Cancer, there is no real difference between what normal prostate cells look like under a microscope with a little or a lot of pomegranate extract; it doesn’t seem to have much of an effect on healthy cells. However, prostate cancer cells are decimated by pomegranate extract—at least in a petri dish, but what about in a person? If these results translated to the clinic, it could be dramatic, but we first need to try it out in people.

“Primary management of prostate cancer…consists of either radical surgery or radiation therapy.” Despite this, “a significant number of patients relapse and ultimately develop metastatic disease.” Even after radical prostatectomy, the cancer comes back in about one-third of the patients, as evidenced by rising prostate-specific antigen (PSA) levels. At that point, the treatment options are limited as the prostate has already been removed. The next step is essentially chemical castration, or hormonal ablation. Just like breast cancer can thrive on estrogen, prostate cancer can thrive on testosterone. We can try to wipe out testosterone, but that can have such negative side effects that anything we can do to delay that would be good. 

So, what about plants? Men in Asia appear to have the lowest prostate cancer rates in the world, up to ten times lower than men in North America. Is this simply because of genetics? No. When Japanese individuals move to the United States and start living and eating like us, their breast and prostate cancer rates shoot right up toward ours. It could be because of what they start eating more of: animal products, which are the strongest risk factor for prostate cancer worldwide on a country-by-country basis. Or, it could be because of what they’re eating less of in the United States, namely their traditional low-fat, high-fiber, generally plant-rich diet with soy products and green tea. So, did the researchers put the cancer patients on a plant-based diet? No, they just had them drink a cup of pomegranate juice every day. Why? Because the study was funded by a pomegranate juice company.

In the three years leading up to the study, participants’ cancer was steadily growing, as measured by the increase in their average PSA levels. Once they started the juice, their tumors continued to grow, but it looked like they were growing slower. In contrast, Dean Ornish and his colleagues got an apparent reversal in early prostate cancer growth with a plant-based diet and other healthy lifestyle changes. Indeed, PSA didn’t just go up slower—it trended down. And, when dripping the blood of the men on prostate cancer cells growing in a lab, the blood serum of those eating healthfully suppressed cancer growth nearly eight times better, whereas the blood of the men on the pomegranate juice suppressed cancer growth by only about 12 percent. Still, to see any effect from drinking a cup of juice a day is pretty impressive.

The problem is that there was no control group in the pomegranate juice study. We could say the patients acted as their own controls, before and after. It’s probably not just a coincidence that their tumors started growing slower right when they started the juice. But, a drug trial tried to do the same thing—treat men with recurring prostate cancer after surgery or radiation. In the drug group, tumor growth slowed in 55 percent of the men. A pretty effective drug, right? Well, the sugar pill worked 73 percent of the time. The placebo effect can be so powerful that it may slow cancer growth. This is why we need placebo-controlled trials. Maybe tricking people into drinking pomegranate-flavored Kool-Aid would have had the same effect. We don’t know until we put it to the test.

Finally, researchers did a randomized, controlled trial of pomegranate juice for prostate cancer, and the daily pomegranate intake had no impact. What do they mean, no impact? Twenty-five percent of the cancer patients appeared to shrink their tumors as soon as they started drinking the pomegranate juice, but 35 percent shrunk their tumors not drinking pomegranate juice. So, any effect appears just to be a placebo. It’s the same story with pomegranate extract pills: They seemed to work until they went head to head with sugar pills and fell flat on their face.


I love pomegranates! Unfortunately, the juice and extracts look no more promising today than when I produced my video Is Pomegranate Juice That Wonderful?.

For some foods that may actually affect prostate cancer progression, see:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

We Have Specific Fruit and Vegetable Receptors

According to a recent survey, the number of Americans adults who say they are eating ‘pretty much whatever they want’ is at an all-time high,” which unfortunately includes “too few fruits and vegetables,” as well as “too little variety.” Half of all fruit servings are taken up by just six foods: orange juice, bananas, apple juice, apples, grapes, and watermelons. Only five foods—iceberg lettuce, frozen potatoes, fresh potatoes, potato chips, and canned tomatoes—make up half of all vegetable servings. We’re not only eating too few fruits and veggies. We’re also missing out on the healthiest fruits, which are berries, and the healthiest vegetables, which are dark green leafies. The fruit and vegetable palette for our palate is sadly lacking.

Why does dietary diversity matter? As I discuss in my video Specific Receptors for Specific Fruits and Vegetables, different foods may affect different problems. Cabbage, cauliflower, broccoli, and Brussels sprouts are associated with lower risk of colon cancer in the middle and right side of our body, whereas risk of colon cancer further down on the left side of our body appears to be better lowered by carrots, pumpkins, and apples. So, “different F/V [fruits and vegetables] may confer different risks for cancer” of different parts of even the same organ.

Variety is the spice of life—and may prolong it. “Independent from quantity of consumption, variety in fruit and vegetable consumption may decrease lung cancer risk,” meaning if two people eat the same number of fruits and vegetables, the one eating a greater variety may be at lower risk.

It’s not just cancer risk. In a study of thousands of men and women, a greater quantity of vegetables and a greater variety may independently be beneficial for reducing the risk of type 2 diabetes. Even after removing the effects of quantity, “each different additional two item per week increase in variety of F&V [fruit and vegetable] intake was associated with an 8% reduction in the incidence of T2D [type 2 diabetes].” Why? Well, it “may be attributable to individual or combined effects of the many different bioactive phytochemicals contained in F&V. Thus, consumption of a wide variety of F&V will increase the likelihood of consuming” more of them.

“All the vegetables may offer protection…against chronic diseases,” but “[e]ach vegetable group contains a unique combination and amount of these [phytonutrients], which distinguishes them from other groups and vegetables within their own group.” Indeed, because “each vegetable contains a unique combination of phytonutriceuticals (vitamins, minerals, dietary fiber and phytochemicals), a great diversity of vegetables should be eaten…to get all the health benefits.”

Does it matter, though, if we get alpha-carotene or beta-carotene? Isn’t an antioxidant an antioxidant? No. “It has been shown that phytochemicals bind to specific receptors and proteins” in our bodies. For example, our body appears to have a green tea receptor—that is, a receptor for EGCG, which is a key component of green tea. There are binding proteins for the phytonutrients in grapes, onions, and capers. In my video The Broccoli Receptor: Our First Line of Defense, I talk about the broccoli receptor, for instance. Recently, a cell surface receptor was identified for a nutrient concentrated in apple peels. Importantly, these target proteins are considered indispensable for these plants foods to do what they do, but they can only do it if we actually eat them.

Just like it’s better to eat a whole orange than simply take a vitamin C pill, because, otherwise, we’d miss out on all the other wonderful things in oranges that aren’t in the pill, by just eating an apple, we’re also missing out on all the wonderful things in oranges. When it comes to the unique phytonutrient profile of each fruit and vegetable, it truly is like comparing apples to oranges.


This is one of the reasons I developed my Daily Dozen checklist of foods to incorporate into one’s routine. Download the free iPhone and Android apps, and be sure to watch my video Dr. Greger’s Daily Dozen Checklist.

I discuss how produce variety—not just quality and quantity—may be important in Apples and Oranges: Dietary Diversity and Garden Variety Anti-Inflammation, so I hope you’ll check them out. You can also learn more about why combining certain foods together may be more beneficial than eating them separately in Food Synergy.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

What Happens if You Add Milk to Tea?

Our endothelium, the inner lining of our blood vessels that controls the function of every artery in our body, “appears to play a critical role in a variety of human disorders, including peripheral vascular disease, stroke, heart disease, diabetes, insulin resistance, chronic kidney failure, [cancer, and blood clots]….” Unfortunately, endothelial cells only live about 30 years, and their replacements don’t seem to function as well. So, “[a]s men and women approach the ages of 40 and 50, there is a progressive decline in endothelial function.” At age 50 or 60, we “can no longer tolerate this risk-factor burden that [we] were once able to tolerate at age 10 or 20,” thanks to this progressive decline in endothelial function.

Or, at least, that’s what we used to think.

As I discuss in my video Tea and Artery Function, there are increasing data to suggest that age is not an immutable risk factor—the decline in artery function is not just an inevitable consequence of aging Researchers did not see the same progressive decline in a Chinese population studied. The older Chinese people in their 60s had the arterial function of young folks in their 20s. “These data suggest that progressive endothelial dysfunction is not an inevitable consequence of aging but might be related to prolonged exposure to environmental factors more prevalent in westernized countries than in China.” What could it be? Traditional Chinese diets include green tea, which has been shown to have a beneficial effect on endothelial function within 30 minutes of consumption, lasting about two hours. It wasn’t the caffeine, which alone had no effect. They suspect it was the flavonoid phytonutrients in the leaves.

Black tea appears to work about just as well as green tea, but then why is green tea associated with lower heart disease risk while black tea is not? In fact, in two British studies, tea consumption was associated with an increased risk of coronary artery disease. Maybe it’s because the Brits commonly drink their tea with milk, whereas green tea is typically drank straight? If only there were a country that drank black tea, but without milk. There is. The Netherlands. In those studies, black tea was associated with the same drop in risk as the green tea studies. So, maybe it is the milk. But you can’t really know until you put it to the test.

Researchers found the “addition of milk to black tea completely prevents the biological activity of tea in terms of improvement of endothelial function.” So, that could explain it. It appears the milk protein casein is the culprit, though soy protein was recently found to have the same nutrient binding effect. The European Society of Cardiology issued a press release about the study showing the protective effect of tea “is totally wiped out by adding milk” and suggested consumers should consider cutting down. Milk-drinkers were not amused: “As long as the reported results are not confirmed in a fair number of humans who drink their tea outside the lab setting, we will continue to add milk to ours.” The researchers responded, challenging the notion that their study wasn’t big enough. They had 16 subjects, and the results were highly significant. Across those 16 people, the “addition of milk to tea not only reduced, but completely blunted the effects of tea….The rationale for drinking tea in a lab setting was that only under these conditions could the influence of other beverages and food be controlled for.” They were doing an experiment after all. Were they supposed to drag the equipment to a Starbucks or something?

“As doctors,” the milky tea drinkers asserted, “we would not prescribe a new drug to patients if it was studied only in one small study. In analogy, milk abstinence should not be recommended to tea drinkers…” They apparently were forgetting that the reason we don’t prescribe drugs without overwhelming evidence is that drugs can kill. So the benefits better outweigh the risks, but what’s the downside of a little milk abstinence?


If this is what one plant can do, imagine the effects of a whole diet centered around plant foods. That’s the subject of my video Plant-Based Diets and Artery Function.

Do be careful about green tea from China if you eat the leaves, though. See Lead Contamination of Tea.

I answer other questions you may have about tea in these videos:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations: