Have you ever wondered if there’s a natural way to lower your high blood pressure, guard against Alzheimer's, lose weight, and feel better? Well as it turns out there is. Michael Greger, M.D. FACLM, founder of NutritionFacts.org, and author of the instant New York Times bestseller “How Not to Die” celebrates evidence-based nutrition to add years to our life and life to our years.

Nutrition Facts Grab Bag 22

Today, on the Nutrition Facts Podcast, we look at the effect of heavy metal music, the role that meat plays in triggering Parkinson’s, and the nutritional power of onions.

This episode features audio from The Dangerous Effects of Heavy Metal Music, The Role Meat May Play in Triggering Parkinson’s Disease, and Are Onions Beneficial for Testosterone, Osteoporosis, Allergies, and Cancer?. Visit the video pages for all sources and doctor’s notes related to this podcast.


Let’s say you’re trying to lose 20 pounds – or boost your immunity – or increase your ability to fight Covid – or even cancer. Well – the amazing thing is – with the right diet – you are well on your way to achieving these vital health goals. Welcome to the NutritionFacts podcast. I’m your host Dr. Michael Greger. 

It’s time for the NutritionFacts Grab Bag, where we look at the latest science on a whole variety of topics. In our first story, we’ll look at the dangerous effects of heavy metal music. 

If you search for heavy metal in the National Library of Medicine database, most of what you find is on heavy metal contamination in fish, for example, making it so hard to clearly establish the role of fish in a healthy diet, perhaps helping to explain the quintupling of odds of autoimmune diseases like juvenile arthritis, for instance.

But searching the hazards of heavy metal also pops up entries like this, on the “risks from heavy metal music.” Here, they were talking about traumatic injuries from slamming around, but you’re more likely to get injured at an alternative rock concert. It’s the Goo Goo Dolls you’ve got to worry about, not Nine Inch Nails.

Okay sure, music-induced hearing loss is a serious problem, but that can be from any loud music. It’s interesting that clinical recommendations include the “80–90 rule”: no more than 80 percent of the maximum volume on personal listening devices for no more than 90 minutes a day. But that’s not what the science shows: “do not exceed 60 percent of the maximum volume” may be more evidence-based, but they figure teens would just ignore that, so they came up with more “acceptable” advice.

I assumed I’d see a lot of satanic-panic nonsense from the 80s, where parents bereaved by suicide started suing heavy metal musicians. What kind of evidence did the parents present? There has been little scholarly research, until this study that proceeded to try to correlate the number of statewide heavy metal magazine subscriptions to youth suicide rates. Oh, you’ve got to be kidding.

When researchers called psychiatric institutions, pretending to be parents worried because their son started listening to that heavy metal music––even though they made it clear that their son didn’t exhibit any symptoms of mental illness––no drugs, no alcohol, and was doing fine at school––ten of the twelve facilities believed the son required psychiatric hospitalization. Imagine what that would do to a kid! It turns out if you actually come back a few decades later, metalheads were significantly happier in their youth and appear better psychologically adjusted than their peers.

Some studies were just strange. Do Parkinson’s patients walk better listening to “Yellow Submarine” or “Master of Puppets”?

Other studies were just like, duh. Heavy metal musicians exhibit a higher heart rate than those performing “contemporary Christian.” Not much of a shocker.

Some studies were kind of cute: Influence of music on promoting patient safety during surgery—veterinary patients. Kitties getting spayed with little earphones on their head. It turns out that “Adagio for Strings” may be more relaxing than AC/DC.

A review on music therapy for human patients warned that caution should be exercised when guiding patients in selecting their music, as “chaotic music,” such us hip-hop and metal, is not healing to human cells—with three citations no less, though two of them don’t say anything, and the third is a nursing newsletter merely quoting someone’s opinion.

But I did some digging, and it turns out stomach cancer cells like metal. If you play them “Cannibal Corpse” versus Beethoven, 12 hours of death metal increased their growth in a petri dish (that’s so metal). But who puts headphones on their stomach? Or their chests, for that matter?

While in one study, Mozart killed off one type of breast cancer cell line and not another, in another study, only Beethoven’s Fifth Symphony seemed to work, and Mozart flopped when the petri dishes were surrounded by speakers on a little platform. How do they even get this stuff published?

Anyway, the true danger from heavy metal is headbanging. “Headbanging is a contemporary dance form consisting of abrupt flexion–extension movements of the head, most commonly seen in heavy metal.” The number of avid aficionados is unknown, but some fans might be endangered by indulging excessively. Although generally considered harmless, health complications attributed to this practice include ripping your carotid artery, rupturing your lung, whiplash injury, and neck fracture, or, in this case, a subdural haematoma. This guy reported headbanging at a Motörhead concert, and all that brisk forward and backward acceleration might have ruptured his bridging veins, and caused him to bleed into his skull.

Bridging veins bridge the gap between the brain and the covering that lines the inside of your skull, and if the veins tear, blood can build up under your skull and compress your brain. This bridging vein rupture has been demonstrated on headbanging cadavers (again, a very metal study). It’s been likened to a kind of shaken-baby syndrome in adults.

The researchers conclude that their case serves as evidence in support of Motörhead’s rock-and-roll reputation, but I think the real takeaway is that a potentially dangerous complication like that can result from a seemingly benign activity. And some of the brain bleeds can be massive.

See, you can tear more than just veins. There are two sets of arteries that tunnel into the skull— the carotid arteries in the front and the vertebral arteries in the back—and you can tear both sets. A 15-year-old indulged in headbanging, ripping his carotid artery, which led to a massive stroke. He presented half-paralyzed, unable to speak, and died in a coma within a week.

What about the vertebral arteries in the back? They’re wedged into your skull, rendering them susceptible to shearing forces from extremes of neck motion, and that’s exactly what appeared to happen: a heavy metal drummer tearing the wall of the artery. Now obviously, all this is really rare, probably afflicting less than one in a thousand or so. What can metalheads do to reduce their risk? To prevent injury due to such head-banging, the range of head and neck motion should be reduced; slower-tempo music should replace metal (good luck with that); the frequency of head-banging could be only on every second beat (that’s actually not a bad idea); or personal protective equipment should be used (like a neck brace?).

Little formal injury research has been conducted on the worldwide phenomenon of head-banging; so, researchers constructed a theoretical head-banging model with enough physics terms to make any nerd happy: angular displacement, sinusoidal motion in the sagittal plane, amplitude of the displacement curve. Study participants: head bangers. But you do need a control group: easy listening music.

Head injury curves and neck injury curves, based on head-banging tempo and angular sweep. At an average head-banging tempo, we’re trying to keep the range of motion under 75 degrees. So, to minimize the risk of head and neck injury, head bangers should decrease their range of head and neck motion. “Unfortunately, it is difficult, if not impossible, to change the habits of heavy metal aficionados.” Maybe what we need are metal-studded neck braces.

In our next story, we look at what the gut has to do with developing Parkinson’s disease.

Parkinson’s disease is an ever-worsening neurodegenerative disorder that results in death and affects about 1 in 50 of us when we get older. A small minority of cases are genetic and run in families, but 85 to 90 percent of cases are sporadic, meaning they just seemingly pop up out of nowhere. It’s caused by the death of a certain kind of nerve cell in the brain. Once about 70 percent of them are gone, the symptoms start. Okay, so what kills off those cells? It’s still not completely clear, but the abnormal clumping of a protein called α-synuclein is thought to be involved. Why? Because if you inject blended Parkinson’s brains into the heads of rats or monkeys you can induce Parkinson’s pathology and symptoms, or even just injecting the pure clumped alpha-synuclein (α-synuclein) strands themselves. Okay, but how do these clumps naturally end up in the brain?

It all seems to start in the gut. The part of the brain where the pathology often first shows up is directly connected to the gut, and we have direct evidence of the spread of Parkinson’s pathology from the gastrointestinal tract to the brain. Alpha-synuclein from brains of Parkinson’s patients is taken up in the gut wall and creeps up the vagal nerves from the gut into the brain. But this was in rats. If only we had a way to go back and look at people’s colons before they got Parkinson’s…And indeed, we can. Old colon biopsies were dredged up from people who would later develop Parkinson’s, and years before symptoms arose, you could see the α-synuclein in their gut.

Research supported by the Michael J. Fox Foundation has found that you can reliably distinguish the colons of patients from controls by the presence of the Parkinson’s protein lodged in the gut wall. But how did it get there in the first place? Perhaps vertebrate food products as a potential source of prion-like α-synuclein. Nearly all of the animals with backbones that we eat—cows, chickens, pigs, and fish—express the protein α-synuclein. And so, when we eat common meat products, when we eat skeletal muscle, we’re eating nerves, blood cells, and the muscle cells themselves. Every pound of meat has like a teaspoon to a tablespoon of blood in it, and that alone could be an α-synuclein source to potentially trigger a clumping cascade of our own α-synuclein in the gut. Though it may seem intuitive that dietary α-synuclein could seed this kind of build=up in our gut, what evidence do we have that it’s actually happening?

There’s a surgical procedure called a vagotomy, in which the big nerve that goes from your gut to your brain is cut as an old-timey treatment for stomach ulcers. Would cutting communication between the gut and the brain reduce Parkinson’s risk? Apparently so––suggesting that the gut-to-brain vagal nerve may be critically involved in the development of Parkinson’s disease.

Now, of course, many people regularly consume meat and dairy products, but only a small fraction of the general population will develop Parkinson’s. So, there must be other factors at play that may somehow provide an opportunity for unwanted dietary α-synuclein to enter the host and initiate disease. For example, your gut becomes leakier as you age, so might that play a role? What else makes your gut leaky? Dietary fiber deprivation has also been shown to degrade the intestinal barrier and enhance pathogen entry. So, this all raises possibilities for food-based therapies.

Parkinson’s patients have significantly less Prevotella in their gut, a friendly fiber-eating flora that bolsters your intestinal barrier function. And so, low levels of Prevotella are linked to a leaky gut, which has been linked to intestinal α-synuclein deposition. But fiber-rich foods may bring Prevotella levels back up. Therefore, by adopting a plant-based diet, in addition to getting the beneficial effects of phytonutrients, it’s possible that increasing overall fiber intake may modify the gut microbiome and gut leakiness in beneficial ways.

So, does a vegan diet—one with lots of fiber and no meat—reduce risk for Parkinson’s disease? Parkinson’s does appear to be rare in quasi-vegan cultures, with rates about five times lower in rural sub-Saharan Africa, for instance. Now all this time, we were thinking the benefits seen for Parkinson’s from plant-based diets was due to the antioxidants and anti-inflammatory nature of the animal-free diets. But maybe it’s also due to the increased intestinal exposure to fiber and decreased intestinal exposure to ingested nerves, muscles, and blood.

Finally today, we look at what randomized controlled human trials tell us about the ways we may—or may not—benefit from eating onions.

Onions are potentially a good source of antioxidants, though, interestingly, the antioxidants are concentrated in the outer layers immediately under the papery peel. Unfortunately, most consumers discard these most nutrient-rich outermost layers, thus losing a valuable part. Here are some numbers. More than 10 times more antioxidants in the outer layer of white onions, compared to the core. You’ll also note that yellow onions in general have more antioxidants than white. And red onions beat them both, based on three different antioxidant testing methods. That’s why I always try to buy red. Though red onions are indeed slightly better, yellow or white onions are no slouches, containing considerable levels of antioxidant activity. So, nutritious, sure, but are there any particular clinical benefits to onion consumption?

For example, here’s a review purporting to have evidence that testosterone in males is enhanced by onion, but the researchers were talking about studies like this on the effects of onion juice after testicular torsion…in rats. Who cares what happens after a rat testicle is rotated 720 degrees counterclockwise? (Except, of course, the rat.) You don’t know what happens in people until you put human testes to the test and…onion extracts don’t appear to work.

Okay, what about bone health? Evidently, older white women who consumed onions at least once a day had an overall bone density that was 5 percent greater than individuals who consumed onions no more than once a month (P < 0.03). Now, 5 percent might not sound like a lot, but that improvement in bone density could potentially translate into decreasing their risk of hip fracture by more than 20 percent if, indeed, it was cause and effect.

Daily administration of onion did cause a big bump in bone density. This opens the possibility for a low-cost, safe, and effective nutritional approach to osteoporosis and—you guessed it—in the rat. Another rodent study. Rats!

But finally, here we go. Tremendous strides have been made in treating osteoporosis with drugs, but they have the potential for serious adverse side effects; so, scientists have drawn their attention to natural remedies. So, let’s randomize people to drink onion juice or placebo onion juice. I don’t know what sounds worse: sugary onion juice or fake sugary onion juice. And as if drinking onion juice wasn’t bad enough, it was all for nothing. It didn’t even work.

What about the anti-allergy activities of shallots, and any therapeutic effects on helping allergic runny noses? Sixteen such patients were randomized equally into an antihistamine group, or a group that got antihistamines plus some capsules containing dried shallot powder. And it looked like the shallot group did better, but there was actually no statistically significant difference in total symptoms between the two groups; so, another #OnionFail. There has to be something onions can do.

What about testing the effects of fresh yellow onion consumption on breast cancer patients to try to decrease the toxic effects of a chemotherapy drug called doxorubicin? Unfortunately, no significant benefit was found on decreasing damage to the liver or heart.

But here we go…finally, a clinical benefit to onions. The consumption of fresh yellow onion ameliorates the high blood sugars and insulin resistance in breast cancer patients during doxorubicin-based chemotherapy. Doxorubicin isn’t just toxic to the liver and heart, but it may also contribute to insulin resistance. So, let’s do a randomized, triple-blind, controlled clinical trial randomizing patients to like a whole onion a day or a third of an onion a day. What happened? The high-onion group experienced a significant decrease in blood sugars and insulin resistance compared to the low-onion group. They went up in the low-onion group, but down in the high-onion group. So, make onions your friend. What’s the worst that can happen—a little onion breath and BO? Probably the least of your worries if you have cancer on chemotherapy.

We would love it if you could share with us your stories about reinventing your health through evidence-based nutrition. Go to nutrition facts.org slash testimonials. We may share it on our social media to help inspire others.

To see any graphs, charts, graphics, images, or studies mentioned here, please go to the NutritionFacts podcast landing page. There you’ll find all the detailed information you need – plus links to all of the sources we cite for each of these topics.

For a vital, timely text on the pathogens that cause pandemics – you can order the E-book, audio book, or the hard copy of my latest book “How to Survive a Pandemic.”

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