Inflammation in the Brain: Causes, Consequences, and Solutions | Chris Kresser
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What Causes Inflammation in the Brain, and What Can You Do to Reduce It?

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inflammation in the brain
Many aspects of the modern world can lead to inflammation in the brain, but activities that relax you, improve your mood, and reconnect you with the world can help. iStock/last19

Inflammation can reach your brain, with devastating results. Read on to learn what can cause brain inflammation, the long-term consequences of chronic inflammation, and how to reduce neurological inflammation.

The Inflamed Brain

Inflammation is the body’s first line of immune response. Upon injury or invasion, macrophages, leukocytes, and other innate immune cells rush to the scene. A cascade of cell signaling pathways is activated in the blood to recruit more immune cells, remove the invader or damaged tissue, and increase blood flow to the affected area.

The brain works a bit differently. The blood vessels within the central nervous system (CNS) are separated from peripheral circulation by a very restrictive barrier, called the blood–brain barrier (BBB). The typical blood immune cells can’t pass the BBB. (1) However, chronic, systemic inflammation over time can break down the BBB. When peripheral pro-inflammatory cytokines make their way into the brain’s circulatory system, the brain’s immune response is activated.

Brain cells called microglia are the primary components of the innate immune system in the CNS. Normally, they are just “surveying,” but they can be activated when inflammatory cytokines make their way past the BBB. When activated, microglia recruit more pro-inflammatory cytokines to the scene, and over time this further breaks down the BBB in a positive feedback loop. (2, 3) The result: brain inflammation.

Symptoms of mild brain inflammation can include: (4, 5)

  • Brain fog
  • Slow thinking
  • Fatigue
  • Depression
  • Changes in vision
  • Anxiety

Our diet and lifestyle choices can lead to brain inflammation—which has devastating effects on our health. Check out this article to find out what causes inflammation in the brain and learn how you can prevent it. #optimalhealth #healthylifestyle #chriskresser

Modern Lifestyle Sets the Stage for Brain Inflammation

Many modern chronic diseases and lifestyles contribute to systemic inflammation that results in neurological inflammation and undesirable consequences on the brain.

Poor Gut Health

Small intestinal bacterial overgrowth (SIBO), gut microbiota dysbiosis, gut permeability, and other gut issues can all impact the brain. An unhealthy gut contributes to neurodegenerative diseases including Alzheimer’s disease and Parkinson’s disease. (6)

The gut–brain axis involves two-way communication. The vagus nerve directly links the brain to the gut, sending signaling messages via peptides, inflammatory molecules, and bacterial metabolites. The brain and gut also communicate indirectly. Some molecules in the gut can cross the intestinal barrier, move through the circulatory system, and cross the BBB into the CNS. (7)

The gut can send positive messages, like gallic acid, a metabolite of dietary polyphenols, that elicits desirable brain effects. (8) But, it can also send negative messages, like lipopolysaccharide (LPS), a bacterial metabolite that causes inflammation. (9)

Standard American Diet

I’ve written at great length about the major inflammatory components of the Standard American Diet:

  1. Industrial seed oils (cottonseed, corn, soybean, sunflower, etc.)
  2. Processed sugar
  3. Refined carbohydrates

When ultra-processed foods comprise over half of the average American’s energy intake, (10) it’s no wonder that chronic inflammation and disease are rampant. Diets high in these three foods lead to reduced synaptic plasticity, a process that mediates cognitive function and learning. (11, 12)

Obesity

In obesity, fat cells work harder to store excess energy, which generates an excess of reactive oxygen species (ROS) and triggers inflammatory cascades. As such, obese people have higher levels of inflammatory cytokines, and losing weight can decrease the levels of those cytokines. (13, 14)

This inflammation reaches and impacts the brain. In mice, neuroinflammation is observable even before significant weight gain. Obesity is a known contributing factor to neurological disorders like Alzheimer’s disease, partially through this inflammatory mechanism. (15)

Diabetes and High Blood Sugar

Because the brain is highly aerobic, using about 20 percent of the body’s energy, and because its antioxidant defense is low, the brain is much more susceptible to oxidative damage. (16) In type 2 diabetes, high blood sugar increases the metabolic rate of brain cells. ROS are regular byproducts of cellular respiration, but when the excess ROS can’t be neutralized, oxidative stress occurs. (17) Oxidative stress upregulates inflammatory cytokines and perturbs the gap junctions of the BBB.

People with diabetes have higher inflammatory markers, including interleukin 6, C-reactive protein, and alpha-1-antichymotrypsin. (18) Diabetes and its associated neuroinflammation lead to impaired cognition, brain atrophy, dementia, and neurodegeneration. (19) Some evidence indicates that Alzheimer’s disease can be considered “type 3 diabetes,” driven by insulin resistance in the brain. (20)

Digital Media Revolution

Technology can increase productivity, help people stay in touch with faraway relatives, and keep us informed about the world. But there can be too much of a good thing—and our brains suffer the consequences. Heavy digital media use is associated with poorer memory, increased impulsivity, less empathy, and anxiety. (21) With Google at our fingertips, we don’t “need” to remember as much—we can just quickly “Google it.” With social media and online gaming, we spend less time with real people and more time cyber socializing.

The digital media revolution is changing our brains. Receiving emails, “likes,” or positive comments hack into the reward center of our brains, located in the more impulsive-driven amygdala region. (22) Over time, this can result in increased efficiency of the amygdala reward system, and reduced gray matter in areas of the frontal cortex, which is the region of the brain that drives self-control and decision-making. Heavy internet users show a lower ability to delay gratification, contributing to poor decision-making. (23)

Brain imaging studies reveal startling similarities between heavy digital media users and those who have a substance addiction. (24, 25) These people can suffer “withdrawal” symptoms when they are cut off from the internet. “Gaming disorder” has been recognized as an official medical condition, showing just how serious a problem tech addiction can be for the brain. (26)

Stress

I’ve written at great length about how stress affects health and contributes to disease. Stress triggers the hypothalamus–pituitary–adrenal (HPA) axis to send hormones like cortisol and neurotransmitters like epinephrine directly to the brain. (27)

Stress can also send information through the gut. Microbes manufacture neurotransmitters that are sent through the vagus nerve, and stress can even increase gut permeability, allowing potentially unwanted molecules to enter the bloodstream. (28)

Levels of pro-inflammatory molecules like tumor necrosis factor alpha and interleukin 1 increase under stress. (29) Chronic stress leads to chronic inflammation and is linked to neurological problems like depression, anxiety, and obsessive-compulsive disorder (OCD). (30)

Infections and Toxins

Two other causes of neuroinflammation are toxins and infections. Environmental toxins, like aluminum, and some gut microbiota metabolites, like LPS, can trigger brain inflammation. (31, 32)

Many viral infections can compromise the BBB, activate microglia, and increase brain inflammation, including measles, West Nile virus, Zika virus, and the flu. (33) Viral brain inflammation progresses much more rapidly than the neurological inflammation discussed in other sections of this article. It can quickly lead to encephalitis or meningitis, severe conditions that need immediate attention.

Long-Term Consequences of Inflammation in the Brain

The brain isn’t meant to be chronically inflamed. Inflammation should be an acute, temporary state to neutralize an active threat. Sustained neuroinflammation disrupts neural homeostasis and can lead to long-term health problems, including: (34, 35)

  • Cognitive deficits
  • Neurodegeneration
  • Alzheimer’s disease
  • Parkinson’s disease
  • Multiple sclerosis
  • Amyotrophic lateral sclerosis

How to Reduce Brain Inflammation

Diet and lifestyle affect every aspect of health. Activities/practices that improve your mood, relax you, and reconnect you with the real world will help reduce neuroinflammation and take care of your brain.

TIME Test for Technology

The internet isn’t inherently evil, but too much tech can affect our decision-making, cognition, and self-control.

Prudently evaluate your usage and habits. One method to try is the TIME test for technology, proposed by Dr. David Perlmutter:

  • T: How much Time do you spend with technology? Compare that time to important things in your life. Is it more time than you spend sleeping? More time than you spend with your family?
  • I: Is it Intentional? Is reaching for your phone just a habit, or do you set aside limited intentional times to check email and social media?
  • M: Are you Mindful during technology use?
  • E: Is it Enriching for you? Is your relationship an overall net positive in your life, or does something need to change?

Try adjusting your tech habits to healthier levels or consider a digital detox if you feel like you need a temporary break from technology.

Habit change is a challenge for all of us, and several factors determine whether we’re able to make a long-term shift in our behavior. One component of successful change? Support. 

In the ADAPT Health Coach Training Program, we train health coaches on how to best offer support to their clients during the habit change process. We dive deep into the topics that matter—including technology overuse—and offer evidence-based instruction into the information and skills needed to become a successful health coach. Find out more about our program and see if a future as a health coach is right for you.

Eat Better

Since 20 percent of our body’s energy goes to the brain, what we eat affects our brain health. To help curb systemic inflammation, avoid the top three inflammatory foods rampant in the Standard American Diet: industrial seed oils, processed sugars, and refined carbohydrates. Chronic consumption of these foods can negatively impact cognitive function, learning, and memory. (36)

Focus on nutrient-dense, whole foods to support brain health. Because the brain is extra susceptible to oxidative damage, foods with high levels of antioxidants, like colorful vegetables and berries, will help prevent ROS from overwhelming neuronal cells. For extra support, consider including some nootropics in your diet.

Cultivate Awareness/Mindfulness

Mindfulness is the antidote to today’s rushed, digital world. Practicing mindfulness means setting aside time to be aware of your current thoughts, feelings, sensations, and surrounding environment, instead of worrying about the past or future. Even just 10 minutes of mindfulness practice can reduce stress and dampen inflammation. (37, 38, 39) Additionally, mindfulness protects against cognitive decline. (40)

Spend Time in Nature

Spending time outside is an important part of ancestral health. Exposure to nature strengthens immune function (41, 42), reduces levels of the stress hormone cortisol (43, 44), and even protects against depression and cognitive decline. (45, 46, 47, 48)

Get Enough Sleep

Although we still don’t fully understand the functions of sleep, we know it’s essential for good health. Unfortunately, 70 million Americans suffer from sleep disorders, and approximately one-third of Americans regularly don’t get enough shut-eye. (49, 50) Not getting enough sleep increases inflammation and negatively affects cognitive function. (51, 52, 53) Chronic sleep deprivation is linked to learning deficits, depression, and Alzheimer’s disease. (54, 55) To take care of your body and your brain, make sleep a priority.

Exercise

Regular exercise yields both physical and mental benefits. Specifically, exercise boosts brain-derived neurotrophic factor, a neuron growth factor, improves the brain’s ability to clear waste through the glymphatic system, and reduces BBB permeability. (56, 57, 58) Evidence also shows that exercise decreases neuroinflammation by inhibiting microglial activation. (59)

Forge Supportive Social Connections

Humans are social creatures and, as such, live healthier, happier lives when they have a network of good relationships. Lonely people are more likely to be stressed and suffer from depression or other mental illness. (60) In contrast, people who have a support network tend to have lower levels of inflammatory proteins and stress hormones. (61, 62, 63)

By focusing on making these positive changes, you can potentially reduce the influence of our modern world and protect your brain from the damaging effects of inflammation. 

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