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Brain Fog: A Research-Based Guide to Restoring Mental Clarity

Written by Dr. Ruscio on March 5, 2021

Written by Dr. Ruscio on March 5, 2021 — Reviewed by Hannah Hamlin

Dr. Michael Ruscio is a DC, Naturopathic Practitioner, researcher, and clinician. He serves as an Adjunct Professor at the University of Bridgeport and has published numerous papers in scientific journals as well as the book Healthy Gut, Healthy You. He also founded the Ruscio Institute of Functional Health, where he helps patients with a wide range of GI conditions and serves as the Head of Research.

Brain Fog May Be a Sign That You Need to Improve Your Gut Health

• What Is Brain Fog|
• Patient Challenges|
• What Causes Brain Fog|
• Brain Fog and Alzheimer’s|
• What to Do About Brain Fog|
• The Bottom Line|
• Recommended Products|

Life is demanding enough without the extra challenge of brain fog. When you can’t think clearly, can’t focus, can’t find the right word, and constantly forget why you walked into the kitchen, even simple tasks can seem difficult. Plus brain fog leaves you feeling mentally exhausted. I know this because I’ve struggled with brain fog myself. 

Brain fog is a symptom that we see and treat often in the clinic. And the good news is most patients resolve their brain fog quickly with improved gut health. That’s because even the simplest steps towards better gut health result in less systemic inflammation, less brain inflammation, and, as a result, less brain fog.

In this article, we’ll look at what the research tells us about the causes of brain fog and what you can do to regain your mental clarity. 

What Is Brain Fog?

Brain fog is a very common symptom characterized by slowed or cloudy thinking, forgetfulness, inability to focus, mental fatigue, and poor mental stamina [1]. Brain fog is not associated with any physical abnormalities in the brain [2].

The symptoms of brain fog are found in a wide array of seemingly-unrelated medical conditions and have been reported in patients with:

• Crohn’s disease [3]
• SIBO and IBS [4, 5]
• Celiac disease [6]
• Non-celiac gluten sensitivity [7, 8]
• Hypothyroidism [9, 10]
• Chronic fatigue syndrome [11]
• Fibromyalgia [12]
• Postural orthostatic tachycardia syndrome (POTS) [13]
• Mast cell disorders [14]
• Obesity [15]
• Menopause [16]
• Multiple sclerosis [17]
• Rheumatoid arthritis [18]
• Lupus [2]

Brain fog is also common after chemotherapy treatments and may be called “chemo fog” or “chemo brain” [19]. Recently, chronic brain fog has also been linked to the coronavirus pandemic as one symptom experienced by “COVID long-haulers,” those who recover from a COVID-19 viral infection but continue to have debilitating symptoms [20].

The Challenge for Patients With Brain Fog

Patients looking for medical advice on how to relieve brain fog may feel like their concerns are not taken seriously.

Despite being common and debilitating, brain fog doesn’t always get the attention it deserves. There’s no test or standard treatment for brain fog and there’s little research conducted specifically about brain fog. According to one group of researchers who studied brain fog in celiac patients [6]:

“These mild degradations of cognitive functions, referred to as “brain fog,” are yet to be formally recognized as a medical or psychological condition.”

Because it’s associated with so many other conditions, healthcare practitioners may assume that brain fog is caused by menopause, autoimmune diseases, or one of many other conditions, and conclude that nothing can be done.

But all of this ignores the true mechanisms behind brain fog, which can be addressed and resolved. Let’s take a closer look.

What Causes Brain Fog?

Current research suggests that inflammation in the brain, also known as neuroinflammation, is one of the primary reasons for brain fog [15, 21, 22].

In one small study, researchers gave 20 healthy subjects a variety of cognitive tests, both before and after short-term brain inflammation was induced. The result? A greater cognitive effort was required when subjects were experiencing acute brain inflammation [23].

Inflammation is the immune system’s natural response to protect your body from harmful toxins, bacteria, viruses, and other pathogens. Your brain has its own, separate immune system and extra safeguards to protect this essential organ:

• The blood-brain barrier is regulated by the central nervous system and filters out toxins in the blood, preventing them from circulating in the brain [24].
• Microglial cells are immune cells that are unique to the brain and central nervous system. When these cells sense the presence of harmful substances, they become activated to protect brain cells. However, they can also become over-activated, causing excessive inflammation in the brain.

Brain fog may occur when toxic substances cross the blood-brain barrier, triggering the brain’s immune system and causing inflammation. A number of underlying conditions can drive this process. Let’s explore a few of them.

Gut Imbalances and Leaky Gut 

Research recognizes that imbalances in the gut ecosystem can alter brain function by producing neuroinflammation [25, 26, 27, 8, 9]. Here’s how a gut condition can lead to inflammation in your brain:

1. When bad microorganisms crowd out the healthy bacteria in your gut, your immune system activates to defend your digestive tract from these invaders.
2. This immune response creates inflammation in the intestinal tract.
3. Over time, chronically inflamed intestines become damaged and more permeable, leading to a condition known as “leaky gut.” 
4. A leaky gut allows bacteria, undigested food particles and other toxins to enter the bloodstream.
5. Toxins in your bloodstream can migrate across the blood-brain barrier, where they become neurotoxins.
6. Neurotoxins create inflammation in the brain, leading to brain fog, poor mood, and other neuropsychological symptoms.

Research shows that brain fog is associated with many gut health conditions, including IBS and SIBO [4, 5], Crohn’s disease [3], celiac disease [6], and non-celiac gluten sensitivity [7, 8]. All of these conditions involve imbalances in the gut ecosystem.

Other conditions that are associated with brain fog include hypothyroidism, chronic fatigue syndrome, fibromyalgia, obesity, difficult menopause transition, and rheumatoid arthritis. In many cases, these conditions also involve imbalances in the gut. This suggests that brain fog may not be caused by these health conditions and instead may share the same underlying mechanism: poor gut health.

Gut Imbalances and Liver Dysfunction

Hepatic encephalopathy (HE) is a loss of brain function observed in people with liver disorders. HE can be severe in patients with serious liver disease, resulting in confusion, personality changes, and even coma. However, a milder form of HE, called minimal hepatic encephalopathy (MHE), can be easily recognized as brain fog. 

The job of the liver is to filter toxins from the blood. When the liver is diseased, it can’t fully perform this function, leading to more toxins in the bloodstream which can cross the blood-brain barrier and cause neuroinflammation.

Recent research suggests a connection between MHE and SIBO (small intestine bacterial overgrowth).

Three studies found high rates of SIBO in patients with liver cirrhosis (scarring of liver tissue resulting from chronic liver inflammation) [28, 29, 30]. SIBO rates were higher (88.9% and 55.9%) among cirrhosis patients with MHE. However, a fourth study did not find any indication of SIBO among cirrhosis patients [31].

Additional studies show that rifaximin (an antibiotic used to treat SIBO) significantly improved symptoms of MHE in patients with both liver disease and SIBO [30, 32, 33]. In one of these studies, two groups of cirrhosis patients were treated for different gut imbalances [30]. Patients treated for SIBO showed significant improvement in MHE symptoms. Those treated for H. Pylori did not experience significant improvements.

One group of researchers suggest that “an altered balance of gut microflora might also be involved in HE [34],” suggesting a possible gut-liver-brain connection. It appears that SIBO may play a significant role here. 

Histamine Intolerance and Mast Cell Disorders

Mast cells and histamine are key players in your body’s immune function.

Mast cells are a specific kind of white blood cell that produces histamine and can trigger inflammation in the body and brain. In some cases, mast cells are triggered too often or without appropriate cause, leading to excess histamine levels and inflammation.

Histamine is known for its role in allergic reactions and is the reason you may occasionally take anti-histamine medication. Histamine also acts as a neurotransmitter in the brain and speeds up communications between brain cells. Appropriate levels of histamine help with alertness, learning, and motivation. Excess histamine, however, may contribute to cognitive impairment [15].

Histamine intolerance is a condition of excess histamine in the body. It’s known to produce allergy-like symptoms, such as rashes, hives, racing heart, and joint pain. 

Levels of histamine in the brain can increase as a result of an overactive immune system and mast cell response as well as the intake of foods that contain histamine. Mast cell disorders and histamine intolerance are both known to cause brain fog [21, 15].

Food Sensitivities

Food sensitivities may also trigger inflammation that leads to brain fog. 

For example, brain fog is common in those with celiac disease and non-celiac gluten sensitivity [6, 7, 8]. In both of these conditions, gluten consumption triggers an immune response that creates inflammation in the gut. The process that leads to brain fog unfolds in the same way as with gut imbalances.

One study showed that brain fog resolved in untreated celiac patients after 12 months on a gluten-free diet [6].

Exposure to Toxins

Exposure to other types of toxins is also linked to brain fog. This includes chemotherapy drugs [19] and airborne molds [35]. In these examples, toxins enter the bloodstream through different routes (through IV infusion or by inhaling mycotoxins into the lungs). It seems likely that these toxins also cross the blood-brain-barrier and create inflammation in the brain.

Can Brain Fog Lead to More Serious Cognitive Dysfunction?

Brain fog is a sign that all is not well with your brain health and your overall health. 

Chronic brain inflammation is one of the key factors associated with the development of Alzheimer’s disease. Research suggests that this process starts decades before severe memory loss becomes apparent [36, 37]. Neuroinflammation is also involved with the development of neurodegenerative diseases like MS and ALS.

While there’s no specific evidence that directly links brain fog to the development of more serious cognitive conditions, the evidence is clear that chronic neuroinflammation carries significant risks for brain health in the long term.

What To Do About Brain Fog

In the clinic, the steps we take to improve gut health and reduce inflammation help patients clear up brain fog. For many patients, brain fog starts to lift once they work on improving their diet and lifestyle. 

While supplements can be helpful to reduce inflammation, the most important approaches address the sources of inflammation. Poor diet, too much stress, lack of exercise, and lack of sleep are the big culprits here.

A standard American diet (high in sugar, carbohydrates, unhealthy fats, and processed foods) tends to feed bad bacteria in the gut, initiating the process that leads to neuroinflammation.

An anti-inflammatory diet, such as the Paleo diet, can be very helpful for reducing brain fog. Anti-inflammatory diets focus on fresh, whole foods instead of processed foods. Including sources of omega 3 fatty acids, such as sardines, mackerel, and salmon, was found to be especially helpful for reducing brain fog in patients undergoing chemotherapy [38].

Probiotics can be very helpful for rebalancing the gut ecosystem and preventing inflammatory neurodegeneration [39]. Probiotics have been shown to improve cognition in patients with IBS [40, 41], Fibromyalgia [42], and Alzheimer’s [43, 44].

Other supplements that may help to reduce your overall inflammation are curcumin, fish oil, and resveratrol. Luteolin supplements may also help reduce brain fog [15].

Lifestyle changes that can be very helpful include:

• Getting 7-9 hours of sleep every night
• Getting regular physical activity, such as walking for 30 minutes a day
• Reducing and managing stress as much as possible

While most people will experience considerable improvement with these fundamental steps, some may require further support to identify and treat specific root causes, including: 

• Identifying specific food triggers, such as gluten, FODMAPs, or high-histamine foods
• Treating a gut infection, such as SIBO 
• Getting blood work to test thyroid hormone levels

For more detailed information about resolving brain fog, see our detailed guide. 

If basic dietary and lifestyle changes, combined with probiotics aren’t enough to eliminate your brain fog, our experienced clinical team can help you develop a personalized treatment approach.

The Bottom Line

Brain fog is a distressing symptom that can significantly impact your day-to-day life. It’s important to recognize this cognitive problem as a sign of neuroinflammation and to take steps to improve your brain function and overall wellness.

Common causes of brain fog include gut imbalances, leaky gut, liver dysfunction, SIBO, histamine intolerance, food sensitivities, and exposure to toxins. 

For many who struggle with brain fog, basic dietary and lifestyle changes can help to resolve these issues. Others may need to dig a bit deeper to identify and treat the root causes of mild cognitive dysfunction. Your brain health is important. Take steps to improve your mental clarity today.

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