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:

Vinegar Is Good for You

Vinegar has evidently been used as a weight-loss aid for nearly 200 years. Like hot sauce, it can be a nearly calorie-free way to flavor foods, and all sorts of delicious exotic vinegars—like fig, peach, and pomegranate—are available to choose from. The question, though, is whether there is something special about vinegar that helps with weight loss, which is the topic of my video Does Apple Cider Vinegar Help with Weight Loss?.

Vinegar is defined as simply a dilute solution of acetic acid, which takes energy for our body to metabolize, activating an enzyme called AMPK that is like our body’s fuel gauge. If it senses that we’re low, it amps up energy production and tells the body to stop storing fat and start burning fat. And, so, given our obesity epidemic, “it is crucial that oral compounds with high bioavailability are developed to safely induce chronic AMPK activation,” which would be potentially beneficial for long-term weight loss. There’s no need to develop such a compound, though, if you can buy it in any grocery store.

We know vinegar can activate AMPK in human cells, but is the dose one might get when sprinkling it on a salad enough? If you take endothelial cells (the cells lining our blood vessels) from umbilical cords after babies are born and expose them to various levels of acetate, which is what the acetic acid in vinegar turns into in our stomach, it appears to take a concentration of at least 100 to really get a significant boost in AMPK. So, how much acetate do you get in your bloodstream sprinkling about a tablespoon of vinegar on your salad? You do hit 100, but only for about 15 minutes, and even at that concentration, 10 or 20 minutes exposure doesn’t seem to do much. Now granted, this is determined in a petri dish. What do clinical studies show us?

A double-blind trial was conducted investigating the effects of vinegar intake on the reduction of body fat in overweight men and women. The researchers call them obese, but they were actually slimmer than the average American. In Japan, they call anything over a BMI of 25 obese, whereas the BMI of the average American adult is about 28.6. Nevertheless, they took about 150 overweight individuals and randomly split them into one of three groups: a high-dose vinegar group drinking a beverage containing two tablespoons of apple cider vinegar a day, a low-dose group drinking a beverage containing only one tablespoon of apple cider vinegar a day, and a placebo control group drinking an acidic beverage they developed to taste the same as the vinegar drink but using a different kind of acid so, there was no acetic acid.

There were no other changes in their diet or exercise. In fact, the researchers monitored their diets and gave them all pedometers so they could make sure the only significant difference amongst the three groups was the amount of vinegar they were getting every day. Within just one month, there were statistically significant drops in weight in both vinegar groups compared with placebo, with the high-dose group doing better than the low-dose group, and the weight loss just got better month after month. In fact, by month three, the do-nothing placebo group actually gained weight, as overweight people tend to do, whereas the vinegar groups significantly dropped their weight. Was the weight loss actually significant or just statistically significant? Compared with the placebo group, the two-tablespoons-of-vinegar-a-day group dropped five pounds by the end of the 12 weeks. That may not sound like a lot, but they got that for just pennies a day without removing anything from their diet.

They also got slimmer, losing up to nearly an inch off their waist, suggesting they were losing abdominal fat. The researchers went the extra mile and put it to the test. They put the research subjects through abdominal CT scans to actually measure directly the amount of fat in their bodies before and after. They measured the amount of superficial fat, visceral fat, and total body fat. Superficial fat is the fat under your skin that makes for flabby arms and contributes to cellulite. Visceral fat, on the other hand, is the killer. It’s the fat that builds up around your internal organs that bulges out the belly—and the kind of fat the placebo group was putting on when they were gaining weight. Both the low-dose and high-dose vinegar groups, however, were able to remove about a square inch of visceral fat off that CT scan slice.

Like any weight loss strategy, it only works if you do it. A month after they stopped the vinegar, the weight crept right back, but that’s just additional evidence that the vinegar was working. But how was it working?

A group of researchers in the United Kingdom suggested an explanation: Vinegar beverages are gross. They created vinegar beverages that were so unpleasant the study subjects actually felt nauseated after drinking them and ate less of the meal the researchers provided. So, there you go: Maybe vinegar helps with both appetite control and food intake, though these effects are largely due to the fruity vinegar concoctions invoking feelings of nausea. Is that what was going on in the original study? Were the vinegar groups just eating less? No, the vinegar groups were eating about the same compared with placebo. Same diet, more weight loss––thanks, perhaps, to the acetic acid’s impact on AMPK.

Now, the CT scans make this a very expensive study, so I was not surprised it was funded by a company that sells vinegars, which is good, since we otherwise wouldn’t have these amazing data, but is also bad because it always leaves you wondering whether the funding source somehow manipulated the results. The nice thing about companies funding studies about healthy foods, though, whether it’s some kiwifruit company or the National Watermelon Promotion Board (check out watermelon.org), is, really, what’s the worst that can happen? Here, for example, even if the findings turned out to be bogus and worst comes to worst, your salad would just be tastier.


I’m so excited to finally be getting to this topic. Type “vinegar” into PubMed, the search engine biomedical literature, and 40,000 studies pop up. It took me a while to take it all in, but I’m so glad I did, as it’s something that has caused a shift in my own diet. I now try to add various vinegars every day.

This is the first of a five-part video series. See the other installments:

For more holistic approaches to weight loss, 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: