Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

A regular intake of mushrooms is said to make us healthier, fitter, happier, and help us live longer. But what is the evidence for all of that? Mushrooms are widely cited for their medicinal qualities, yet very few rigorous human intervention studies have been done.

There is a compound called lentinan, extracted from shiitake mushrooms. To get about an ounce, you have to distill around 400 pounds of shiitakes. That’s like 2,000 cups of mushrooms. But then, you can inject the compound into cancer patients, and see what happens. The pooled response from a dozen small clinical trials found that the “objective response rate” was significantly improved when lentinan was added to chemo regimens for lung cancer. Objective response rate means like tumor shrinkage. But what we really care about is survival and quality of life. Does it actually make cancer patients live any longer or any better? Well, those in the lentinan group suffered less chemo-related toxicity to their gut and bone marrow, so that alone might be reason enough to use it. But what about improving survival?

I was excited to see that lentinan evidently could significantly improve survival rates for a type of leukemia. And here it is. Adding lentinan increased average survival, reduced cachexia (which is like cancer-associated muscle wasting), and improved cage-side health. Wait, what? Damn it. This was improved survival for brown Norwegian rats. So, that so-called clinical benefit only applies if you’re a veterinarian.

A compilation of 17 actual human clinical studies did find improvements in one-year survival in advanced cancer patients, but no significant difference in the likelihood of living out to two years. Even the compilations of studies that purport that lentinan offers a significant advantage in terms of survival, are talking about statistical significance. It’s hard even to tell these survival curves apart. Lentinan improved survival by an average of 25 days. Now, 25 days is 25 days, but we should evaluate claims made by companies about the miraculous properties of medicinal mushrooms very critically.

Lentinan has to be injected intravenously. What about mushroom extract supplements you can just take yourself? Shiitake mushroom extract is available through the Internet for the treatment of prostate cancer for approximately $300 a month, so it’s got to be good, right? Men who regularly eat mushrooms do seem to be at lower risk for getting prostate cancer, and not apparently just because they eat less meat or more fruits and vegetables in general.

So, why not give a shiitake mushroom extract a try?  Because it doesn’t work—ineffective in the treatment of clinical prostate cancer. The results demonstrate that complementary and alternative medicine claims can actually be put to the test. What a concept! Maybe it should be mandatory before patients spend large sums of money on unproven treatments––or, in this case, a disproven treatment,

What about God’s mushroom (also known as the mushroom of life) or reishi mushrooms? Conclusions: No significant anticancer effects were found; not even a single partial response. Maybe we’re overthinking it. Plain white button mushroom extracts can kill off prostate cancer cells, at least in a petri dish, but so could the fancy God’s mushroom. But that didn’t end up working in people. You don’t know if plain white button mushrooms work or not, until you put it to the test.

What I like about this study is that the researchers didn’t use a proprietary extract. They just used regular whole mushrooms, dried and powdered—the equivalent to a half cup to a cup and a half of fresh white button mushrooms a day, in other words a totally doable amount. They gave them to men with “biochemically recurrent prostate cancer.” What that means is the men had already gotten a prostatectomy or radiation in an attempt to cut or burn out all the cancer, but now it’s back and growing, as evidenced by a rise in PSA levels, an indicator of prostate cancer progression.

Of the 26 patients who got the button mushroom powder, four appeared to respond, meaning they got a drop in PSA levels by more than 50 percent after starting the shrooms.

Here’s where the four responders started out in the months leading up to starting the mushrooms. Patient 2 was my favorite. He had an exponential increase in PSA levels for a year, and then he started some plain white mushrooms and then boom, his PSA level drops down to zero and stays down. A similar response was seen with patient 1. Patient 4 had a partial response, before his cancer took off again, and Patient 3 appeared to have a delayed partial response.

Now in the majority of cases, the PSA levels continued to rise, not dipping at all. But even if there is only a one in 18 chance you’ll be like these two, with a prolonged complete response that continues to date, we’re not talking about weighing the risks of some toxic chemotherapy for the small chance of benefit, but just eating some inexpensive, easy, tasty plain white mushrooms every day.

Yes, the study didn’t have a control group, and so it may have just been a coincidence, but post-prostatectomy patients with rising PSAs are almost always indicators of cancer progression. And, hey, what’s the downside?

In these two patients, their PSA levels became undetectable, suggesting that the cancer disappeared altogether. They had already gone through surgery, had gotten their primary tumor removed along with their entire prostate, already went through radiation to try to clean up any cancer that remained, and yet the cancer appeared to be surging back—until, that is, they started a little plain mushroom powder.

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