March 12, 2024

“Hi, I’m Ben Greenfield, and I’m naked.”

Thus begins one of my most popular videos on YouTube. Over five million voyeuristic viewers have watched me strip off my clothes, take a deep breath, and step into an icy shower (and yes, it still surprises me how many people need a tutorial on taking a cold shower).

Ever since my early days of 5:00 a.m. morning swims in the surprisingly cold YMCA pool, goosebump-inducing bouts of training for long open water swim competitions and triathlons, along with cold baths, cold river, and lake swims, keeping my home basement office temperature at a shiver-inducing level, swimming in the chilly nineteen-foot endless pool in the forest behind my house, and even talking cryotherapy clinics into allowing me to do back-to-back-to-back sessions while they carefully monitored my skin temperature, I've been a cold aficionado since before cold was… well… cool.

I first became intrigued by cold exposure when, in 2011, I interviewed NASA materials engineer Ray Cronise on my podcast. Ray also penned a fascinating article in Wired magazine, describing how he created the “Shiver System” — a protocol to help people lose over 20 pounds of fat per month by taking a cold shower at the beginning and end of each day.

Later, I discovered more about the effects of cold exposure when neurosurgeon Dr. Jack Kruse explained to me how he uses cold-water exposure with his patients to heal nerves and brain damage. Then, journalist James Nestor, author of the captivating book Deep, informed me of the beneficial brain changes that occur in freedivers and humans when they immerse themselves in cold water.

I was convinced. Not only did I journey to Fort Lauderdale, Florida, to spend a full week learning to free dive and spearfish in deep, cold water, but I also began to experiment with chanting, meditation, deep breathing, and even fancy electronic vagus nerve stimulators like the Circadia, Pulsetto, and TruVaga, all to increase the integrity of the blood-brain barrier (BBB) — one part of the human nervous system that is vital but often neglected.

Regarding your mental function, supporting the BBB is one of the most important steps you can take, and maintaining it properly requires far more than mere cold therapy. When the BBB is compromised, the brain is exposed to invaders such as toxins and bacteria. This can cause inflammation in the brain, and long-term, chronic inflammation in the brain can result in dementia, Alzheimer’s, and other neurodegenerative diseases, as well as less serious problems like brain fog, lack of focus, poor sleep, and food cravings.

In this article, you’ll discover why I wander out for chilly winter morning walks in a T-shirt and shorts, why I begin and end each day with a refreshing cold shower, why I go out of my way to hop into a cold lake, river, ocean, or ice bath once a week, and why cryotherapy chambers are not just gimmicky ways to spend valuable cash on a sexy new social media profile pic.

What Is a Leaky Brain?

To understand why the BBB is so critical, let’s look first at what can happen when something goes wrong. 

Chances are, you have heard of the gastrointestinal condition known as leaky gut. If you are a wellness enthusiast or you lurk on health forums, you may have already heard leaky gut described as “intestinal permeability.” But the truth is that your gut is naturally and selectively permeable, allowing nutrients to pass into your bloodstream while keeping harmful toxins, large allergenic proteins, and pathogens out. When this process fails because your gut lining has been damaged by compounds such as herbicides, pesticides, excessive alcohol, sugar, and a variety of other assailants, your gut lining becomes more permeable than it should be, and you end up with a leaky gut. This can lead to indigestion, poor nutrient absorption, the development of food sensitivities, and systemic inflammation.

Similarly, when your BBB is punctured or damaged, you can end up with a leaky brain.

No, a leaky brain has nothing to do with the zombie apocalypse or gray matter oozing out your ears. The reality is much easier to digest and is based on the fact that your brain is very similar to your gut in at least one respect: it’s protected by a membrane, the BBB, that’s also selectively permeable.

Your brain requires compounds such as glucose, amino acids, fat-soluble nutrients, and ketones to function properly, so the BBB needs to allow them to pass through. For example, caffeine crosses the barrier quite easily and can benefit brain health. At the same time, your brain also relies on the BBB to keep out harmful toxins, infectious pathogens, and rogue immune cells.

The BBB is formed by brain capillary endothelial cells, which are simple squamous (flat) cells that line the walls of blood and lymphatic vessels. The entire barrier includes three mechanisms that control the exchange of materials between your blood, brain, and cerebrospinal fluid and maintain the extracellular environment of the central nervous system:

1. The cells that form the physical barrier between your blood and your brain
2. Transporter molecules that mediate the flow of compounds between your brain and blood
3. Enzymes in the endothelial cells of the brain and epithelial cells of the blood that metabolize neurotransmitters and toxins

To understand the delicacy of this barrier, you have to understand that the endothelial lining of your blood vessels is only one cell thick — that’s about one-tenth the thickness of a single strand of hair. Some of the largest vessels, such as arteries and veins, are also surrounded by thick walls of connective tissue and smooth muscle cells, but the vessel walls themselves are lined only by this thin sheet of cells.

Like every other cell in your body, endothelial cells can divide. The division of endothelial cells can help to quickly repair blood vessel walls. If left to themselves, they can live from a couple of months (liver endothelium) to several years (brain endothelium).

But when they are exposed to harmful compounds or stressors such as excessive inflammation, these cells can die prematurely and are forced to divide quickly to replicate in adequate quantity to repair the vessel wall. But when the vessel wall is exposed to a stressed state 24/7 without any breaks, the vessels that make up the BBB gradually weaken.

13 Tips for Healing a Leaky Brain

There are plenty of measures you can take to prevent BBB permeability, repair holes that may already be there, and maintain the integrity of your endothelium. The following are thirteen ways to fix a leaky brain.

1. Get More Sleep

Sleep loss is known to impair the immune system and increase levels of pro-inflammatory mediators. Sleep loss also increases sympathetic, “fight-or-flight” nervous system activity and causes endothelial dysfunction — which limits the ability of the cells that make up the BBB to divide and repair.

To maintain the health of your BBB, you need to get a good amount of sleep each day (between seven and nine hours per 24-hour period). A small dose of melatonin — 0.2 to 0.3mg — half an hour before bed can help restore optimal BBB permeability and maintain its integrity, likely due to melatonin’s impressive anti-inflammatory and sleep-promoting properties.

After discovering this strategy from Dr. John Lieurance, a repeat guest on my podcast who has appeared here, here, here, and here, and a friend whom I call the “Dr. Strange” of alternative medicine, I often use a sleep sledgehammer dose of melatonin suppositories and patches while traveling (up to 600mg for the first few nights after arriving at a new destination). In addition, NAD and creatine supplementation can assist with the blood-brain barrier damage induced by a poor night of sleep. 

2. Limit Your Alcohol Intake

Alcohol consumption is a major contributor to a leaky brain because of the formation of reactive oxygen species (ROS), which are highly reactive molecules containing oxygen that are naturally produced in the body as a byproduct of normal metabolism. When ROS levels become too high due to factors such as environmental stressors, poor diet, or certain medications, they can cause damage to cellular structures like proteins, lipids, and DNA, leading to oxidative stress and potentially contributing to various diseases and aging processes. Additionally, high levels of ROS can cause damage to the BBB and pass compounds such as acetaldehyde — a toxic byproduct of alcohol metabolism — across the BBB and into the brain.

Sure, the low dose of ethanol from a glass of wine a day can migrate across the BBB, triggering the release of good endorphins and stimulating relaxing neurotransmitter receptors. However, higher amounts of alcohol can result in damage from ethanol and acetaldehyde.

So as much as possible, limit yourself to no more than one serving of alcohol per day — preferably not of the giant fishbowl-size wineglass variety. If you opt to drink, consider alcohol-free or low-alcohol nighttime cocktail alternatives such as ketone esters, herbal liquors, or bitters and digestifs mixed with soda water, electrolytes, and splashes of fresh fruit juice.

A few of my favorite options include:

• KetoneAid ketone cocktails (use code Ben for free shipping)
• Tēthos tea-based non-alcoholic beverages (use code BENGREENFIELD to save 10%)
• Ebo Lebo (Italian)
• Pelinkovac (Croatian)
• Apple cider vinegar in soda water with a squeeze of lemon
• Vinegar-based shrubs (check out Boundless Cookbook and Boundless Kitchen for tons of healthy cocktail and mocktail options)

3. Control Blood Pressure

Both acute and chronic hypertension increase BBB permeability. Dark chocolate, magnesium, potassium, handgrip strength training, and even high-dose garlic can all help reduce blood pressure. If you’re worried about your breath after consuming garlic, rest assured that you don’t have to mow through an entire bowl of elephant garlic to reap its benefits. Taking a supplement of allicin, the main bioactive component of garlic, is a far more efficient way to get the brain-boosting benefits of garlic without acquiring vampire-killing breath.

As far as handgrip devices go, you can take a Captains of Crush grip strengthener with you in the car or on an airplane or train. There is also a handgrip smart device called Zona that has been clinically approved for treating blood pressure and guides you through a squeeze-and-relax regimen.

Finally, do not restrict salt as a blood pressure-lowering strategy. A good mineral-rich salt is crucial for maintaining normal blood volume, blood pressure, and oxygen delivery to tissues. (For more on the myths behind salt consumption, I cannot recommend highly enough that you read Dr. James DiNicolantonio’s book The Salt Fix.)

4. Be Cautious with High-Fat Diets

In one study, rodents who were given a diet containing 40 percent saturated fat experienced elevated BBB permeability. The deleterious effects of saturated fats on brain health can be even more serious if you happen to be a carrier of the APOE4 genotype, which significantly increases your risk of Alzheimer’s and impairs the brain's transport of docosahexaenoic acid (DHA) — an omega-3 fatty acid that is crucial for brain health.

But if you happen to be a high-fat, low-carb, or keto diet enthusiast, there are ways to mitigate this damage. For example, limiting alcohol consumption and adding aged garlic extract, alpha-lipoic acid (particularly R-ALA, its more biologically active form), niacin, NAD, bitter melon, or vitamin D can be effective.

Phytonutrient-rich plants and spices such as turmeric, astragalus, and cruciferous veggies like broccoli, brussels sprouts, and cabbage produce a similar protective effect. Fiber-rich foods such as sweet potatoes, purple potatoes, yams, and beans are also helpful, as is fish consumption.

What’s most important for you to know is that you should ideally avoid a low-carb or “dirty keto” diet chock-full of butter, coconut oil, lard, and fat-streaked slabs of red meat limited in fiber and greens, and instead — if you choose to limit carbs — adopt a more Mediterranean approach rich in omega-3 fatty acids such as fish, avocados and olives, a wide variety of bitters, herbs and spices, fermented vegetables, tannin and polyphenol-rich beverages, and low-sugar, nutrient-dense fruits such as berries and pomegranates.

5. Drink Coffee and Tea

Caffeine is a known protector of BBB integrity, and a cup of clean, organic coffee a day, or around 100 to 200mg of caffeine per day, may even help inhibit BBB disruption, which could be one way that coffee helps prevent Alzheimer’s disease. Caffeine induces the production of cyclic adenosine monophosphate (cAMP), a molecule that facilitates intercellular communication and fortifies the tight junctions of the BBB. 

In addition, cAMP reduces inflammation in the brain. You can get a good, healthy dose of caffeine from an 8-ounce cup of coffee or green tea. Just be sure to choose low-mold and organic varieties, since many mycotoxins and metabolites secreted by molds can translocate through the BBB and cause neuroinflammation.

6. Take Specific Supplements

Alpha-GPC, a type of choline that readily crosses the BBB, is known to improve endothelial dysfunction. Inositol from egg yolks or inositol supplements also enhances BBB integrity. Berberine reduces BBB permeability and increases resistance to brain damage following head trauma. Vitamins B12, B6, and B9 restore a damaged BBB to equilibrium.

Research has shown that individuals who have had a stroke may have some success repairing their BBBs by using herbs and supplements such as astragalus, chlorogenic acid, ginseng, olive leaf extract, and rosmarinic acid. In addition, individuals who have had head injuries and suffer from a leaky brain have been shown to benefit from apigenin, butyrate, citicoline, and shilajit.

You can also use nutrients and supplements to help inhibit matrix metalloproteinase-9 (MMP-9), those enzymes that, in the presence of inflammation, can break down parts of the BBB — inhibitors of MMP-9 have been shown to restore BBB integrity. These inhibitors include curcumin, resveratrol, berberine, fish oil, ginger, broccoli, watercress, pomegranate extract, and many other natural anti-inflammatories found in fruits, vegetables, herbs, and spices.

Peptides, which are short chains of amino acids available as oral, injectable, or, most notably, nasal spray delivery mechanisms, can also assist with BBB integrity. A few of the more notable peptides in this respect, which can also act like relatively potent nootropics or smart drugs, are Semax, Selank, P21, Adamax, BPC-157, VIP, GHK-CU, Dihexa, and Cerebrolysin (I recommend checking out the peptides from Limitless Life Nootropics — use code BEN to save 15%).

7. Get More Magnesium

Adequate magnesium intake, between 300 and 600mg a day, can attenuate BBB permeability — in a study, even people who were injected with an agent to induce leaky BBBs benefited from magnesium. You can get magnesium into your system by taking it orally, soaking in magnesium salts baths, or applying magnesium topically, as either a lotion or spray, on the back of your neck and head.

Make sure to track how much magnesium you take in total, including all these applications, because in amounts over 1,500mg per day, magnesium can cause annoying loose stools. Magnesium L-threonate is the best form — it can cross the blood-brain barrier and most effectively increase magnesium levels in the brain.

8. Stimulate Your Vagus Nerve

The vagus nerve is the largest nerve in your body and runs from your brain to your ears, tongue, lungs, and gut. It is the backbone of your parasympathetic nervous system, and its health goes hand in hand with both emotional and gastric health. Multiple studies have shown that stimulating the vagus nerve strengthens the BBB.

You can naturally stimulate the nerve with practices like massages, singing, chanting, meditation, deep breathing, and cold showers. A good vagus nerve stimulator device that delivers electrical impulses to the vagus nerve, such as the Fisher Wallace Stimulator, TruVaga, or Pulsetto device, can also work quite well, as can red-light therapy devices that can treat the neck and jaw area, particularly the Vielight or Kineon devices.

9. Avoid Frequent Snacking

Ghrelin, a hunger-stimulating hormone, can improve BBB integrity. Research has shown that ghrelin can reduce BBB breakdown after traumatic head injury. By maintaining a moderate weight without yo-yo dieting, avoiding long fasting periods, eating adequate protein (0.7 to 0.8g per pound of body weight per day), and getting enough sleep, you can normalize your ghrelin levels.

10. Nourish Your Gut Bacteria

One study observed the effects of a transplant of gut bacteria from healthy mice with perfect BBB integrity to unhealthy mice with leaky brains. The researchers found that the transplant restored the integrity of the damaged barriers because of specific inflammation-modulating compounds released by bacteria that increase BBB integrity.

Fortunately, you don’t have to hunt down a willing donor to give you a healthy poop transplant (although so-called “fecal microbiota transplants” are increasingly available and affordable). You can achieve similar repair results by avoiding stress, limiting antibiotic use, eating enough fiber, and taking quality probiotics such as Seed's DS-01® (use code 25BEN to save 25 percent off your first month). Also, look for “synbiotics” that have both bacteria and bacteria food, and eat a wide variety of fermented foods regularly.

11. Decrease Inflammation

According to Dr. Datis Kharrazian, a medical researcher specializing in chronic disease and nutrition, inflammatory cytokines — molecules that promote inflammation — that start in an inflamed gut can enter the bloodstream, make their way to the brain, and pass through even a healthy blood-brain barrier. Once in the brain, these cytokines can affect sensitive tissues, most notably the vagus nerve and autonomic nervous system, to the point that they cannot function properly.

Both the vagus nerve and the autonomic nervous system play a major role in regulating the movement of food through the gut, so when they’re not working properly, intestinal motility slows down. In a sort of vicious cycle, once intestinal motility slows down, the inflammatory cytokines in the intestines have even more time to make their way into the bloodstream and from there pass through the blood-brain barrier, creating a cycle of continuing inflammation and worsening intestinal function.

Because poor vagal nerve tone can increase both cortisol and inflammatory cytokines, Dr. Kharrazian recommends stimulating the vagus nerve to reboot it, through singing, gargling, and gagging exercises, along with coffee enemas. In addition, one of the best ways to manage inflammation is to support your mitochondria, which operate a bit like cellular engines.

But in the process of creating adenosine triphosphate (ATP) energy, which is the “energy currency” of the cell, these engines give off exhaust known as reactive oxygen species (ROS). Your body creates compounds to neutralize that exhaust, such as glutathione, catalase, and superoxide dismutase, but produces far fewer of these compounds with age, triggering an issue known as inflammation, which is a root cause of most chronic diseases of aging, such as cancer, Alzheimer's, and heart disease.

So in addition to supporting your vagus nerve, you should support your mitochondria with strategies such as:

• NAD
• CoQ10
• Alpha lipoic acid (ALA)
• L-carnitine (especially the injectable kind)
• Creatine
• High-intensity interval training
• Cold therapy
• Hyperbaric oxygen (HBOT)
• Exercise with oxygen therapy (EWOT)
• Sauna
• Methylene blue combined with red-light therapy
• Peptides like MOTS-c and epitalon
• And — a personal favorite of mine — the powerful intranasal peptide VIP (vasoactive intestinal polypeptide)

12. Don’t Heat Your Head

The influence of electromagnetic radiation on the function of the BBB has been researched since the 1970s on animals, cell cultures, and recently, humans. Electromagnetic fields (EMFs), such as those produced by microwaves, Wi-Fi routers, and other elements of the electrical soup, don’t seem to produce significant thermic heating of brain tissue that can make the BBB more permeable, but unfortunately, the practice of holding your smartphone up to your head or sleeping with your device on non-airplane-mode in close proximity to your head does.

A multitude of studies now show that harmful biological changes in brain tissue can occur at much lower radiation levels of specific absorption rate (SAR) than the FCC and FDA claim are safe and that radiofrequency waves from a phone within 12 inches of the head can increase brain tissue temperature to unsafe levels. Even though there’s no hard evidence (yet!) that Bluetooth earbuds are also a problem, I personally engage in smart risk reduction:

• I always use my phone in speaker mode or with old-school wired headphones.
• I rarely use Bluetooth earbuds or headphones.
• For long calls, I use airtube headphone technology, which allows sound to travel through non-wired hollow tubes. 

13. Cold Thermogenesis 

By engaging in regular cold exposure such as cold soaks, cold showers, splashing cold water on your face, cold walks in minimal clothing, wearing body-cooling gear like the Cool Fat Burner vest, standing in cryotherapy chambers, and even keeping your home a bit chillier than is comfortable, you can:

• Restore BBB health by causing increased blood flow and nitric oxide delivery to your brain, which increases BBB integrity and suppresses BBB degeneration
• Increase cell longevity
• Support a robust immune system
• Induce rapid fat loss in the absence of exercise
• Lower your appetite and strengthen the appetite-regulating vagus nerve connection between the gut and brain
• Cause internal temperature fluctuations that will send blood and nitric oxide to your brain 

One simple option is to use Ray Cronise’s “Shiver System,” a five-minute cold shower at the beginning and end of the day. It involves alternating between twenty seconds of cold water and ten seconds of warm water ten times through. If this sounds boring or monotonous to you, get a waterproof MP3 player or learn some rollicking shower songs.

Another option is a dip in the Morozko Forge, which is a prebuilt eight-foot-long ice bath that uses chlorine-free ozone treatment combined with an advanced water cooling system to maintain water temperatures as low as 32 degrees Fahrenheit — even in hot summer conditions of up to 110 degrees Fahrenheit.

Alternatively, for some DIY options, you can use my fellow biohacker Luke Storey’s budget freezer hack or my friend and music producer Rick Rubin’s slightly spendier luxury chiller system.

Interestingly, these types of strategies are all the more crucial for children. After all, babies aren’t born with a BBB! If a leaky BBB makes an adult highly susceptible to toxins, chemicals, and other environmental and food-based pollutants, it really makes you rethink how you should optimally care for a newborn child, eh?

Finally, I’m often asked if cold water post-exercise can somehow “blunt” the responses to exercise such as mitochondrial biogenesis or satellite cell proliferation and muscle growth, kind of like high-dose antioxidants such as vitamin C and E can do. The proposed mechanism of action for this effect is that cold water can shut down the body’s own inflammatory processes so effectively that an exercise response just doesn’t occur.

The fact is, you have to get very cold for this to happen — typically experiencing a drop in core temperature that takes 10 or more minutes at less than 45 degrees Fahrenheit, which most people just aren’t doing after a workout. If you do want to take a long cold soak, just save it for at least 2 hours pre- or postworkout. 

Leaky Brain No More — How to Begin Repairing Your BBB Now

You don’t want to associate the word leaky with any part of your body. After reading this article, you may be worried that you have somehow done irreparable damage to a delicate structure in your brain. But the good news is that your endothelial cells are designed to quickly regenerate and patch holes in your BBB. All you need to do is follow the tips in this article to give your body the environment that allows this repair to occur.

In the same way that a sound intestinal lining is necessary for optimized digestion and nutrient absorption, an intact and correctly functioning BBB is critical for precise cognitive performance. 

The health of the vagus nerve, a raging appetite, and normalized blood pressure are all critical to a healthy BBB.

Guess what addresses all three?

Cold showers, cold head dunks, or cold water splashed on the face. Each morning for the next week, try to take a two-to-five-minute cold shower, get your head under cold water, or splash cold water on your face ten to twenty times.

If you enjoyed this article on fixing any leaky brain issues you might be experiencing, I put together a few resources that'll kickstart your healing journey:

• Boundless (this article is just a small glimpse of what is found in the book chapter “38 Degrees Below Zero: How to Fix a Leaky Brain,” which maps out how to restore your BBB)
• Biohacking Your Brain With Precision Medicine, Genomics, Psychedelics, Advanced Nutritional Strategies & Much More!
• How To Unlock Your Brain’s Full Potential, Biohacks To Unleash Your Mind, The “Secret Sauce” For Healing A Leaky Gut & More With Dr. Greg Kelly.
• How To Build An Unbeatable Brain (Ben Greenfield's Full SEALFit Unbeatable Mind Presentation)

Plus — this is big — to help you begin incorporating many of the recommendations I provided in this article, I created Ben Greenfield's Brain Boost Blueprint, which is a special guide full of biohacks designed to help protect and optimize your brain (not to mention, it is full of exclusive discounts).

It's completely free, with no strings attached (meaning you don't have to enter your email address to get it), so check it out here.