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:

How Much Vinegar Every Day?

Consuming vinegar with a meal reduces the spike in blood sugar, insulin, and triglycerides, and it appears to work particularly well in those who are insulin resistant and on their way to type 2 diabetes. No wonder the consumption of vinegar with meals was used as a folk medicine for the treatment of diabetes before diabetes drugs were invented.

Many cultures have taken advantage of this fact by mixing vinegar with high glycemic foods. For example, in Japan, they use vinegar in rice to make sushi, and, in the Mediterranean, they dip bread into balsamic vinegar. Throughout Europe, a variety of sourdough breads can lower both blood sugar and insulin spikes. You can get the same effect by adding vinegar to boiled white potatoes then cooling them to make potato salad.

Adding vinegar to white bread doesn’t just lower blood sugar and insulin responses—it increases satiety, or the feeling of being full after a meal. As you can see in my video Optimal Vinegar Dose, a study found that if you eat three slices of white bread, it may fill you up a little, but in less than two hours, you’re hungrier than when you began eating. If you eat that same amount of bread with some vinegar, though, you feel twice as full and, even two hours later, still feel nearly just as full as if you had just eaten the three pieces of bread plain. But this remarkable increase and prolongation of satiety took nearly two tablespoons of vinegar. That’s a lot of vinegar. What’s the minimum amount?

It turns out that even just two teaspoons of vinegar with a meal can significantly decrease the blood sugar spike of a refined carb meal, a bagel and juice, for instance. You could easily add two teaspoons of vinaigrette to a little side salad or two teaspoons of vinegar to some tea with lemon. Or even better you could scrap the bagel with juice and just have some oatmeal with berries instead.

What if you consume vinegar every day for months? Researchers at Arizona State University randomized pre-diabetics to take daily either a bottle of an apple cider vinegar drink—a half bottle at lunch, and the remaining half at dinner—or an apple cider vinegar tablet, which was pretty much considered to be a placebo control: While the bottled drink contained two tablespoons of vinegar, the two tablets only contained about one third of a teaspoon. So in effect, the study was comparing about 40 spoonfuls of vinegar a week to 2 spoonfuls for 12 weeks.

What happened? On the vinegar drink, fasting blood sugars dropped by 16 points within one week. How significant is a drop of 16 points? Well this simple dietary tweak of a tablespoon of vinegar twice a day worked better than the leading drugs like Glucophage and Avandia. “This effect of vinegar is particularly noteworthy when comparing the cost, access, and toxicities” associated with pharmaceutical medications. So the vinegar is safer, cheaper, and more effective. This could explain why it’s been used medicinally since antiquity. Interestingly, even the tiny amount of vinegar in pill form seemed to help a bit. That’s astonishing. And, no: The study was not funded by a vinegar company.

What about long-term vinegar use in those with full-blown diabetes? To investigate this, researchers randomized subjects into one of three groups. One group took two tablespoons of vinegar twice a day, with lunch and supper. Another group ate two dill pickles a day, which each contained about a half tablespoon’s worth of vinegar. A third group took one vinegar pill twice a day, each containing only one sixteenth of a teaspoon’s worth of vinegar. I wasn’t surprised that the small dose in the pill didn’t work, but neither did the pickles. Maybe one tablespoon a day isn’t enough for diabetics? Regardless, the  vinegar did work. This was all the more impressive because the diabetics were mostly well controlled on medication and still saw an additional benefit from the vinegar.


Make sure to check out my other videos on vinegar’s benefits:

This vinegar effect seems a little too good to be true. There have to be some downsides, right? I cover the caveats in Vinegar Mechanisms and Side Effects.

There are a few other foods found to improve blood sugar levels:

The best approach, of course, is a diet full of healthy foods:

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: