You all know about intestinal permeability, or “leaky gut.” The job of the gut lining is to be selectively permeable, allowing helpful things passage into the body and preventing harmful things from getting in. Nutrients get through, toxins and pathogens do not. Leaky gut describes the failure of this vetting process. But what about “leaky brain”?
A similarly dynamic barrier lies between the brain and the rest of the body: the blood-brain barrier. Since the brain is the seat of all the conscious machinations and subconscious processes that comprise human existence, anything attempting entry receives severe scrutiny. We want to admit glucose, amino acids, fat-soluble nutrients, and ketones . We want to reject toxins, pathogens, and errant immune cells. Think of the blood-brain barrier like the cordon of guards keeping the drunken rabble from spilling over into the VIP room in a nightclub.
The blood-brain barrier (or BBB) can get leaky, just like the gut lining. This is bad.
More generally, the BBB regulates passage of inflammatory cytokines into the brain, prevents fluctuations in serum composition from affecting brain levels, and protects against environmental toxins and infectious pathogens from reaching the brain. A leaky BBB means the floodgates are open for all manner of unpleasantries to enter the brain.
Some pathogens even wield chemical weaponry that blasts open the blood-brain barrier, giving them—and anything else in the vicinity—access to the brain. To prepare for that, you must support the integrity of your blood-brain barrier.
Optimize your B vitamin intake
In adults with normal B vitamin levels, mild cognitive impairment, high homocysteine levels, and a leaky BBB, taking vitamins B12, B6, and B9 (folate) restored the integrity of the blood-brain barrier .
Review this post  and make sure you’re getting the B vitamins you need. Primal folks tend to overlook them.
Nourish your gut
A leaky gut accompanies, and maybe causes, a leaky brain. Funny how that works, eh?
It’s a rodent study , but it’s quite illustrative: a fecal transplant  from healthy mice with pristine BBB integrity to unhealthy mice with leaky BBB and pathogen-filled guts restored the integrity of the blood-brain barrier.
DIY fecal transplants are an extreme intervention. Until that becomes more feasible, simply eating more prebiotic fiber , experimenting with resistant starch , taking a quality probiotic , and eating fermented foods  on a regular basis will get you most of the way there.
Eat plenty of magnesium
Okay, Sisson. Enough already with the magnesium. We get it! But magnesium can attenuate  BBB permeability, even if you inject an agent explicitly designed to induce leaky blood-brain barriers .
This is yet another reason to eat enough magnesium-rich foods (like spinach, almonds, blackstrap molasses, winter squash), drink magnesium-rich mineral water (I love Gerolsteiner, but you can also just go down to the local Euro food market and check the labels for high-Mg waters), or take a good magnesium supplement (anything ending in “-ate” like magnesium glycinate or citrate).
Don’t eat a 40% cocoa butter diet
Rodents given a 40% saturated fat (from cocoa butter) diet experienced elevated BBB permeability .
Except wait: The remaining 60% of calories was split up between white sugar, wheat starch, casein, and dextrin (PDF ). So this isn’t the type of 40% SFA diet you folks are eating.
Except wait again: Adding in either aged garlic extract, alpha lipoic acid (ALA), niacin, or nicotinamide completely abolished the increase in permeability.
It looks like a refined diet high in saturated fat and sugar/starch and absent any phytonutrient-rich plant foods like garlic or antioxidant supplements like ALA will cause elevated BBB permeability (in rodents). I’m not sure I’d recommend a 40% SFA diet either way, however. Balance is probably better .
Use phytonutrient-rich plants and spices
Recall the study from the last section where some garlic extract was enough to eliminate the bad BBB effects of a refined lab diet. That’s because aged garlic extract is particularly rich in phytonutrients with strong antioxidant effects. What about other fruits, vegetables, and spices with different phytonutrients—do those also help BBB function?
Curcumin  (from turmeric ) certainly helps . Astragalus root, used in many ancient medical traditions, can help . Sulforaphane, from cruciferous veggies  like broccoli, Brussels sprouts, and cabbage, shows promise .
Drink coffee and/or tea
As phytonutrient-rich plants, they technically belong in the previous section, but coffee  and tea  are so special that they deserve their own space. Both are sources of caffeine , a noted protector of BBB integrity .
Supplements can help
Supplement forms of the aforementioned nutrients are worth a look. Also:
Alpha-GPC (a type of choline that readily crosses the blood-brain barrier) has been shown to reduce BBB permeability  in hypertensive rats.
Inositol (which you can get from foods like egg yolks but not in very large amounts) improves BBB integrity . Another option is to consume phytate-containing foods; if you’ve got the right gut bacteria, you can convert phytate into inositol .
Berberine, noted anti-diabetic compound, reduces BBB permeability  and increases resistance to brain damage following head trauma.
Control your blood pressure
Both acute  and chronic hypertension  increase BBB permeability. This means you’ll have to control your sleep  and stress . You’ll need to reduce insulin resistance . Eat dark chocolate  (the horror). Figure out if you’re salt-sensitive  (you may even have to increase salt intake if it’s too low). Get enough magnesium (yes, again) and potassium .
Sleep really is everything. You can’t avoid it, and if you skimp on it, things fall apart. The blood-brain barrier is no exception: sleep restriction impairs BBB function and increases permeability .
Don’t drink too much alcohol
Alcohol is a tough one. While I just wrote a big post explaining the merits of wine consumption , ethanol is undoubtedly a poison in high doses, and I derived real benefits when I gave it up for a few months . One way alcohol exerts its negative effects is by inducing BBB dysfunction . This allows both the pleasant effects of alcohol (low-dose ethanol migrating across the BBB and directly interacting with neurons, triggering endorphins and interacting with GABA receptors) and the negative effects (high-dose ethanol migrating across the BBB to damage the neurons, leaving the door open long enough for immune cells to sneak in and cause all sorts of trouble ).
Stimulate your vagal nerve
After a traumatic brain injury or stroke, the resultant increase in BBB permeability floods the brain with inflammatory cytokines, causes swelling and neuronal death, and worsens the prognosis. Stimulating the vagal nerve after such an injury decreases the BBB permeability  and improves the prognosis.
One treatment for epilepsy is to wear vagal nerve stimulators which send light electronic pulses to the nerve, akin to a pacemaker for the brain. Easier options include humming, cold water exposure  (even just splashing the face can help), singing, chanting, meditating , deep breathing , coughing, moving your bowels  (or summoning the same abdominal pressure required for said movement; girding your core for a heavy squat or deadlift should also work along the same lines), and many more.
Perhaps an entire post on the vagal nerve is in order. It’s an interesting area that impacts more than just the BBB.
Stop eating so often
Ghrelin is the hunger hormone. When you haven’t eaten in a while, ghrelin tells you that it’s time to eat. It also increases blood-brain barrier stability  after (again) a traumatic brain injury.
So, never eat? No. But make sure to feel actual hunger. It’s the best spice , and it confers a whole host of other benefits, including better blood-brain barrier function. Heck, try intermittent fasting  for the ultimate boost to ghrelin.
You might notice that a lot of the studies I cite involve traumatic brain injuries to rodents. Dropping a weight on a rat’s head or triggering a stroke in a mouse are two of the most reliable ways to induce BBB permeability. Brain injuries are also quite common in humans, and the BBB permeability that results is a major therapeutic target, but we can’t study it so easily in people. While acute and chronic BBB permeability are different beasts, and mice are not men, they operate along the same rough pathway.
That’s about it for today, folks. I hope you feel encouraged and able to fortify your blood-brain barrier. Don’t wait for cognitive decline to set in. Get started now.
How do you improve the integrity of your blood-brain barrier? Have you even considered it prior to today?
Thanks for reading!