Leaky Brain, Leaky Gut: Are They Real?

First there was leaky gut; now there’s leaky brain. These questionable concepts are being promoted by practitioners of so-called “functional medicine.”

Is your brain leaking? Probably not

First there was leaky gut 

Three years ago Mark Crislip wrote about leaky gut syndrome for SBM. He said, “because of an almost complete lack of supporting basic science and few therapeutic clinical trials showing no effect, virtually no physician who has an understanding of the gastrointestinal physiology gives the disease credence.” Nothing has changed.

Intestinal permeability is a real thing, but according to this review article “these terms are poorly defined, their assessment is a matter of debate, and their clinical significance is not clearly established.” Leaky gut syndrome, on the other hand, is a fad diagnosis not accepted by mainstream medicine. The Canadian Gastrointestinal Society calls it a myth:

The Myth: According to the proponents of leaky gut syndrome, bacteria and toxins enter the bloodstream through these defective tight junctions and wreak havoc throughout the body, causing bloating, gas, cramps, inflammatory bowel disease (IBD), as well as fatigue, food sensitivities, joint pain, moodiness, irritability, sleeplessness, autism, and skin problems like eczema and psoriasis.

Debunked: This is all speculation, as scientific studies do not validate any of these claims. It is extremely dangerous that a TV doctor personality and some otherwise trusted practitioners are diagnosing and treating this baseless ‘syndrome’.

An article from the NHS agrees:

While it’s true that some conditions and medications can cause a “leaky” gut (what scientists call increased intestinal permeability), there is currently little evidence to support the theory that a porous bowel is the direct cause of any significant, widespread problems.

There is also little evidence that the “treatments” some people claim help to reduce bowel leakiness, such as nutritional supplements and herbal remedies, have any beneficial effect for most of the conditions they supposedly help.

Now there’s “leaky brain”

The same “leaky gut” ideas are now being applied to the brain, blaming all kinds of symptoms on substances leaking through a faulty blood-brain barrier (BBB).

Sometimes I think I have a leaky brain. Memories and facts have leaked out and been lost. And after my recent fall and head injury, a brain CT scan clearly showed that blood had leaked out into the subarachnoid spaces and other areas where it did not belong. But that’s not what functional medicine doctors mean by leaky brain. They are not talking about anything leaking out but rather things leaking into the brain because a defective blood-brain barrier is not doing its job to keep those unwanted things out.

What science says about the blood-brain barrier

An excellent review article explains what science has learned about the BBB and the questions that remain. The small blood vessels of the central nervous system (CNS) have unique properties. They regulate the movement of molecules, ions, and cells between the blood and the CNS. The BBB is a complex regulatory system: some components of the blood (oxygen, some gases, lipid-soluble molecules) diffuse freely into the brain; some molecules that the brain needs (glucose, for example) are actively transported into the brain; some molecules do not pass at all.

The BBB is both a blessing and a curse. A blessing because it regulates brain homeostasis and protects the brain from toxins and pathogens. A curse because it presents an obstacle to drug delivery to the brain.

The review article explains that the BBB is altered with inflammation, injury, and degenerative processes. We know that BBB dysfunction is associated with certain neurologic diseases like multiple sclerosis, Alzheimer’s, and epilepsy; but we don’t know whether the BBB dysfunction is a cause or a result of those diseases. We suspect that some of the changes are healing and others are pathological; we suspect that many different mechanisms are involved. We still don’t understand how alterations in the BBB affect neuronal activity, brain function, and behavior. In neurologic diseases, we don’t know whether BBB changes are due to loss of maintenance signals or to the presence of disruptive signals.

What functional medicine says about leaky brain

In the book Why Isn’t My Brain Working? a chiropractor claims that memory loss, difficulty focusing and concentrating, brain fog, depression, anxiety, fatigue, loss of zest for life, and loss of motivation are all signs that your brain is degenerating. He explains that modern diets, a stressful lifestyle, and environmental toxins are responsible; he tells readers how to properly care for and feed the brain to prevent degenerative diseases like Alzheimer’s, Parkinson’s, and MS. The book is long on speculation and advice but short on evidence.

One alternative medicine website claims that when the BBB is compromised,

the brain is vulnerable to damage from chemicals, inflammatory cytokines, and immune cells. This causes brain fog (cognitive dysfunction), chronic fatigue, anxiety/depression, neurodegenerative diseases, and other neurological conditions.

It recommends how to fix leaky brain at the root causes:

  • An anti-inflammatory diet (avoiding lectin, gluten, high-calorie and high-fat foods)
  • Normalize blood sugar
  • Deal with infections and toxins
  • Reduce stress
  • Avoid sleep loss
  • Healthy brain circulation
  • Reduce homocysteine levels
  • Reduce glutamate levels
  • Lose weight

(Most of these are good general health recommendations; the others are questionable.)

It lists supplements that may help repair a damaged BBB:

  • Acetyl L-carnitine
  • Alpha lipoic acid
  • Alpha GPC
  • Angelica (Dong Quai) extracts
  • Astragalus
  • Astaxanthin
  • Apigenin
  • B12-B6- Folate Mix
  • Berberine
  • Bitter melon
  • Butyrate
  • Chlorogenic acid
  • Citicoline
  • Collagen
  • Curcumin
  • Vitamin D3
  • Ellagic acid
  • Fish oil
  • Ginseng
  • Goji fruit
  • Hydrogen-rich water
  • Licorice
  • Lycopene
  • Myoinositol
  • Magnesium
  • Melatonin
  • Methylene blue
  • Oxaloacetate
  • Feverfew
  • Progesterone
  • Pterostilbene
  • Resveratrol
  • Rosmarinic acid
  • Shilajit
  • Selenium
  • Sulforaphane
  • Ursolic acid

How do they know this? They are mainly extrapolating from mouse and rat studies. There is no evidence from clinical trials to suggest benefits for humans or to determine appropriate dosages. They don’t actually make any recommendations for humans to take any of these.

It lists supplements that may disrupt the BBB in some circumstances: andrographis, L-arginine, nicotine, and zinc. The evidence it offers is from cell culture and rat studies.

It lists drugs that help protect and repair the BBB, but says, “Currently, the only conventional therapy to help improve the blood-brain barrier integrity is glucocorticoids (synthetic cortisone) treatments.”

Another website repeats much of this questionable information and adds a few more very questionable recommendations: take probiotics, drink coffee, avoid alcohol, avoid environmental mold and mycotoxins, reduce exposure to electromagnetic fields (EMFs), and avoid gluten.
Yet another website recommends the natural medicines apigenin, baicalein, catechins, curcumin, luteolin, resveratrol, and rutin. It recommends you ask your doctor about getting lab tests to assess your BBB, your microbiome, and yeast overgrowth. Recommended tests include homocysteine, blood sugar, and antibodies against occludin and zonulin. It recommends exercise. Finally, it recommends consulting a functional medicine doctor who will customize diagnostics and natural protocols based on your unique needs.

The notorious functional medicine guru Mark Hyman has a “Broken Brain” video series which I reviewed in a previous SBM article. In that article, I also covered the fallacies of functional medicine. Hyman also has a podcast discussing leaky brain – with a chiropractor!

Conclusion: a questionable concept

While there are documented defects in the BBB associated with some diseases, the concept of “leaky brain syndrome” appears to be a bogus diagnosis created by the functional medicine industry. It attributes all manner of symptoms to a leaky BBB, and claims a leaky brain is the cause of chronic neurodegenerative diseases. These ideas are not supported by acceptable scientific evidence: they rely on questionable evidence from animal and in vitro studies, speculations about basic science, and a lot of imagination. “Leaky brain” gives functional medicine doctors the excuse to read unwarranted conclusions into non-standard lab tests and to play trial-and-error with patients on a long-term basis, experimenting with diet, lifestyle changes, and dietary supplements. The patients may appreciate the attention, but there is no evidence that the functional medicine approach actually heals a defective BBB or provides any objective improvement in clinical outcomes. Or that the symptoms they are treating actually have anything to do with a leaky BBB. Neither leaky gut syndrome nor leaky brain syndrome are recognized by mainstream medicine. They are fantasies from alternative, complementary, integrative, and functional medicine.

This article was originally published in the Science-Based Medicine Blog.

Dr. Hall is a contributing editor to both Skeptic magazine and the Skeptical Inquirer. She is a weekly contributor to the Science-Based Medicine Blog and is one of its editors. She has also contributed to Quackwatch and to a number of other respected journals and publications. She is the author of Women Aren’t Supposed to Fly: The Memoirs of a Female Flight Surgeon and co-author of the textbook, Consumer Health: A Guide to Intelligent Decisions.

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