The Benefits of Slow Breathing

There are all manner of purported hiccup “cures,” which include everything from chewing on a lemon, inhaling pepper, or, our dog’s favorite, eating a spoonful of peanut butter. In my video How to Strengthen the Mind-Body Connection, I talk about the technique I’m excited to try the next time I get hiccups: “supra-supramaximal inspiration,” where you take a very deep breath, hold for ten seconds, then, without exhaling, breathe in even more and hold for another five seconds, and then take one final, tiny breath in and hold for five last seconds to achieve “an immediate and permanent termination to hiccups…”

When I was a kid, I taught myself to control my own hiccups using slow-paced breathing, and, as an adult, was so excited to see there was finally a case report written up on it.

There’s a nerve—the vagus nerve—that goes directly from our brain, to our chest, and to our stomach, connecting our brain back and forth to our heart and our gut, and even to our immune system. The vagus nerve is like the “‘hard-wired’ connection” that allows our brain to turn down inflammation within our body. When you hear about the mind-body connection, that’s what the vagus nerve is and does. “There has been increasing interest in treating a wide range of disorders with implanted pacemaker-like devices for stimulating the vagal afferent [vagus nerve] pathways,” but certain Eastern traditions like Yoga, QiGong, and Zen figured a way to do it without having electrodes implanted into your body.  

“A healthy heart is not a metronome,” as a study titled exactly that explains. “Your heart rate goes up and down with your breathing. When you breathe in, your heart rate tends to go up. When you breathe out, your heart rate tends to go down.” Test this out on yourself right now by feeling your pulse change as you breathe in and out.

Isn’t that remarkable?

That heart-rate variability is a measure of vagal tone—the activity of your vagus nerve. Next time you’re bored, try to make your heart rate speed up and slow down as much as possible within each breath. This can be done because there’s an entirely other oscillating cycle going on at the same time, as you can see at 2:08 in my video, which is the speeding up and then slowing down of your heart rate, based on moment-to-moment changes in your blood pressure. And, as any physics student can tell you, “all oscillating feedback systems with a constant delay have the characteristic of resonance,” meaning you can boost the amplitude if you get the cycles in sync. It’s like pushing your kid on a swing: If you get the timing just right, you can boost them higher and higher. Similarly, if you breathe in and out at just the right frequency, you can force the cycles in sync and boost your heart rate variability, as you can see at 2:36 in my video.

And what’s the benefit again? According to the neurophysiologic model postulation it allows us to affect the function of our autonomic nervous system via vagal afferents to brainstem nuclei like the locus coeruleus, activating hypothalamic vigilance areas.


In other words, it’s not just about curing hiccups. Practicing slow breathing a few minutes a day may have lasting beneficial effects on a number of medical and emotional disorders, including asthma, irritable bowel syndrome, fibromyalgia, and depression. In the United States, we’ve also put it to use to improve batting performance in baseball.

To date, most studies have lacked proper controls and have used fancy biofeedback machines to determine each person’s resonant frequency, but, for most people, it comes out to be about five and a half breaths per minute, which is a full breath in and out about every 11 seconds. You can see the graph at 3:34 in my video. When musicians were randomized into slow-breathing groups with or without biofeedback, slow breathing helped regardless. It’s the same with high blood pressure. As you can see at 3:52 in my video, you can use this technique to significantly drop your blood pressure within minutes. The hope is if you practice this a few minutes every day, you can have long-lasting effects the rest of the day breathing normally.

Practice what exactly? Slow breathing—taking five or six breaths per minute, split equally between breathing in and breathing out. So, that’s five seconds in, then five seconds out, all the while breathing “shallowly and naturally.” You don’t want to hyperventilate, so just take natural, shallow breaths, but be sure to simply breathe really slowly. Try it the next time you get hiccups. Works for me every time!

For more tips, watch my video on How to Stop Hiccups.

And, because slowing down our pulse in general may also have beneficial effects, I encourage you to check out:

Every time I’m amazed by ancient wisdom, I have to remind myself of the video I did on toxic heavy metals—Get the Lead Out. So, though traditional healing methods may offer a plethora of insights, they still need to be put to the test.

In health,
Michael Greger, M.D.

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

The Benefits of Vinegar Beyond Weight Loss

A double-blind, placebo-controlled, randomized study found that body weight and belly fat were significantly reduced by adding just a single tablespoon of vinegar to one’s daily diet. Is there any benefit to vinegar consumption if you’re not overweight? Well, the subjects’ triglycerides normalized, and, for those taking the larger dose of two tablespoons per day, there was a dip in blood pressure. Those effects may have just been because of the weight loss, though. Other than taste, is there any benefit to normal-weight individuals sprinkling vinegar on their salads? What about vinegar for controlling blood sugar? That’s the topic of my video Can Vinegar Help with Blood Sugar Control?.

If you feed people a half cup of table sugar, as their blood sugars spike, their artery function can become impaired. The higher the blood sugars go, the more the arteries take a hit. There’s a drug, though, that can block sugar absorption. By blunting the blood sugar spike with this drug, you can prevent the arterial dysfunction. This demonstrates that it’s probably good for your heart if you don’t have big blood sugar spikes after meals. In fact, how high your blood sugars spike after a meal is a predictor for cardiovascular mortality. So do people who eat lots of high glycemic foods, like sugary foods and refined grains, tend to have more heart attacks and strokes? Yes. They also appear more likely to get diabetes—but maybe people who eat lots of Frosted Flakes and Wonder Bread have other bad dietary habits as well?

The diets that have been put to the test in randomized controlled trials and proven to prevent diabetes are the ones focusing on cutting down on saturated fat and ramping up the consumption of fiber-rich whole plant foods, such as fruits, vegetables, and whole grains, without specific regard to lower or higher glycemic loads. The drug has been put to the test, though, and blunting one’s mealtime blood sugar spikes does seem to reduce the risk of developing diabetes, as well as reduce the risk of heart attacks and high blood pressure. So is there any way to prevent these blood sugar spikes without having to take drugs? Well, one way would be to not sit down to a half cup of sugar!

Yes, the drug can slow the progression of your atherosclerosis. You can see in my video Can Vinegar Help with Blood Sugar Control? how the arteries going to your brain narrow somewhat more slowly with the drug than without it. But wouldn’t it be better to eat a diet that actually reverses heart disease and diabetes? The healthiest diet to prevent the meal-related blood sugar and fat spikes—the oxidation and inflammation—is a diet centered around whole plant foods. But what if you really want a bagel? Instead of spreading drugs on it, spreading on some almond butter may help blunt the blood sugar spike from refined carbs. Another option is to dip your baguette in some balsamic vinegar.

“The consumption of vinegar with meals was used as a home remedy for diabetes before the advent of pharmacologic glucose-lowering therapy”—that is, before drugs came along—but it wasn’t put to the test until 1988. After all, how much money can be made from vinegar? Well, according to The Vinegar Institute, millions of dollars can be made! But a single diabetes drug, like Rezulin, can pull in billions—that is, until it was pulled from the market for killing too many people by shutting down their livers. The drug company still made out like a bandit, though, having to pay out less than a billion to the grieving families for covering up the danger.

There’s no liver failure from schmearing peanut butter on a bagel, though, and it cuts the blood sugar response in half. Similarly, drinking four teaspoons of apple cider vinegar diluted in water gives the same blunting of the spike—with the additional advantage over the peanut butter of lowering insulin levels in the blood. This is something peanut butter apparently can’t do. But putting peanut butter on your bagel is presumably better than having a bagel with lox because fish causes triple the insulin response. Red wine also increases insulin levels, though not as much as fish does, and also shoots up triglycerides. Non-alcoholic red wine, however, doesn’t cause the same problem.

What about vinegar? Not only may a tablespoon a day tend to improve cholesterol and triglycerides over time, vinegar can drop triglycerides within an hour of a meal, as well as decrease blood sugars and the insulin spike, potentially offering the best of all worlds.

Was that bursting with information or what? It’s because of everyone’s kind support that I was able to hire more than a dozen researchers to help me plow through the literature. I’m extremely grateful so many of you were able to see the potential and help become what it is today. Onward and upward!

What’s that about belly fat being reduced? Check out other videos in my series on vinegar:

Did I say reverse diabetes? Reverse heart disease? For examples, see:

Sharing information that can help people prevent and reverse common diseases is my life’s work. Check out the full story in my series of introductory 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:


Using a Smell Test to Diagnose Alzheimer’s Disease

Alzheimer’s disease (AD) pathology appears to start in the part of the brain that handles smell before subsequently spreading to additional brain regions and then, ultimately, taking over much of the rest of the brain. This led some to speculate that Alzheimer’s disease may begin in the nose. Perhaps there’s some environmental agent that might enter the brain through some portal in the nostrils?

This is the so-called olfactory vector hypothesis. The anatomy of the nose is well suited for the transfer of things directly into the brain, since the olfactory nerves that stick out into the nose project directly into the brain, bypassing the blood-brain barrier. The nose was actually a major infection route for the polio virus. Public health officials you started cauterizing the nasal passages of schoolchildren by spraying caustic chemicals up their noses in an effort to prevent the disease.

The concern is if people breathe in some ionized metals like aluminum dust, for example, it could be transported into the brain through these olfactory nerves at a rate of about 2 millimeters an hour, which is practically 2 inches a day. Doubt has been cast on this theory, however, by a case report of a woman born with a birth defect in which she had no smell nerves yet still developed Alzheimer’s-like pathology. And so, to date, all the supporting evidence is really just circumstantial. It is clear, though, that changes in the sense of smell is among the first clinical signs of Alzheimer’s, occurring during the preclinical phase—that is, before there’s any noticeable cognitive decline. Could we use these changes to predict or diagnose the disease?

For years, researchers have been trying to find markers of brain illness hidden in people’s ability to smell using all sorts of fancy gadgets. For example, functional MRI scans can detect differences in brain activation in response to an odor. In my video, Peanut Butter Smell Test for Alzheimer’s, you can see the responses to lavender. You’ll see a representation of a normal brain’s responses to the odor versus an Alzheimer’s brain. This unequivocally demonstrates that we can pick up changes in smell function due to Alzheimer’s. But do we really need a million-dollar machine?

An ingenious group of researchers at the University of Florida discovered all we may need is some peanut butter and a ruler.

Considering that the left side of the brain primarily processes what we smell through our left nostril and the right side of our brain covers the right nostril, and understanding that Alzheimer’s strikes the left side more than the right, what if you performed the following experiment: Close your eyes and mouth, breathe normally through the nose, then close one nostril, and hold a foot-long ruler out from the open nostril. Once your eyes, mouth, and one nostril are closed, open a container of peanut butter at the bottom of the ruler (one foot away from your open nostril). Move the peanut butter closer by 1 centimeter upon each exhale until you can detect the odor. Then repeat the whole procedure again using your other nostril.

This is exactly what the University of Florida researchers did with their subjects. What did they find? The normal elderly control subjects in the study smelled the peanut butter as soon as it came within an average of 18 centimeters (about 7 inches) from either nostril. It was about the same, roughly 7 inches, in the right nostrils of Alzheimer’s patients. But in their left nostrils, it was a mere 2 inches! The peanut butter had to be only 2 inches away before the Alzheimer’s patients could detect it through their left nostrils. This happened every single time. Indeed, the researchers found that a “left nostril impairment of odor detection was present in all the patients with probable AD.” There was no left-right difference in the control group; they could smell the peanut butter when it was the same distance away from both their left and right nostrils. In the Alzheimer’s group, however, there was a 12-centimeter difference.

The disparity was so great that we may be able to set a cutoff value for the diagnosis of Alzheimer’s. The researchers reported that “[c]ompared to patients with other causes of dementia this nostril asymmetry of odor detection…was 100% sensitive and 100% specific for probable AD,” meaning no false positives and no false negatives. Compared to healthy people, it was 100% sensitive in picking up cases of probable Alzheimer’s and 92% specific. What exactly does that mean? In this study, if you had Alzheimer’s, there was a 100% chance of having that wide left-right discrepancy. But, if you did have that discrepancy, the chance of having Alzheimer’s was only 92%. This means there were some false positives.

The reason it’s only “probable” Alzheimer’s is because the only way we can really confirm someone has the disease is on autopsy. The current criteria for diagnosing Alzheimer’s require an extensive evaluation, combined with fancy positron emission tomography (PET) scans and spinal taps. All of these tests are expensive and hard to get, can be invasive, and can have potential complications. On top of that, they are neither highly sensitive nor specific. The left-right nostril / peanut butter odor detection test, however, was fast, simple, non-invasive, and inexpensive. They concluded that may make peanut butter an ideal instrument for the early detection of Alzheimer’s disease.

Does all this sound a bit too good to be true? It may be. A University of Pennsylvania research team was unable to replicate the results. Click here to read their paper. So at this point, the data are mixed. I’ll do another post once more studies are published and we have a better handle on whether it’s useful or not.

Of course, it’s better to prevent Alzheimer’s in the first place. Check out these videos for more information.

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: