These 7 Things Are Killing Your Brain

From the foods we eat and the stress we carry to our social lives and sunlight exposure, there are many factors playing a role in how healthy—or not—our brains are. If you experience brain fog, mental sluggishness, poor recall, or simply want to prevent future cognitive loss, look out for these seven things that might be killing your brain.   

Brain Killer #1: Poor Nutrition

The trifecta of ultra-processed, overly sweet, and fried foods significantly contributes to many health conditions—including poor brain function. While a piece of candy or a basket of French fries every once in a while won’t kill your brain, repeated and chronic exposure to these highly processed foods loaded with sugar, refined carbohydrates, salt, or fried omega-6 oils can definitely have a detrimental effect on how your brain works—and how you feel. 

High amounts of refined sugars or carbohydrates—like candy, soda, sports drinks, desserts, cakes, crackers, white bread, and pasta—can disrupt your body’s normal glucose metabolism and insulin response, leading to insulin resistance. When cells in the body—including brain cells—become resistant to insulin, neuron functioning begins to decline. Research has verified the link between insulin resistance and cognitive loss, which may be mediated partly by increased levels of inflammation. 

We know that high intake of sugar and fried foods can lead to chronic inflammation in the body, as both types of foods lead to the formation of AGEs (advanced glycation end products) and free radicals, which are harmful compounds that can damage proteins in the brain. AGEs are an aptly named molecule, as they significantly age the brain and lead to neurodegenerative conditions. 

Some studies have shown that eating a diet high in sugar (especially fructose) can impair memory and learning, as excess sugar interferes with BDNF (brain-derived neurotrophic factor) production, a molecule necessary for maintaining and growing new brain cells. Plus, ultra-processed and fried foods are typically low in essential nutrients and bioactive compounds like vitamins, minerals, and antioxidants, contributing to an increased risk of cognitive decline and poor mental functioning. 

Brain Killer #2: Low-Quality Sleep

Poor sleep is one of the quickest ways to impact your cognition and mood negatively—both in the short-term and long-term. You probably have learned firsthand that your next-day performance and emotional state can be affected by how you sleep—but cognitive health as we age can also be affected when we chronically get poor sleep.

One way that sleep impacts our brain is through the glymphatic system—a series of channels that carry fresh cerebrospinal fluid into the brain and flush out waste- and toxin-filled fluid, effectively “cleaning the brain.” However, this primarily occurs during deep sleep. One toxin that gets removed by the glymphatic system is beta-amyloid—a protein that is commonly associated with neurodegenerative conditions.

Studies show that both too little and too much sleep can negatively impact cognition. The sweet spot for adults over age 65 is 7 to 8 hours of sleep, while younger or middle-aged adults may require up to 9 hours of high-quality sleep per night, which includes cycling through REM, deep, and light sleep. Research published in the journal Sleep showed that adults over age 65 who slept less than 7 hours or more than 8 hours had lower cognitive scores than those sleeping in the 7 to 8-hour range.

Brain Killer #3: Drinking Excess Alcohol

Drinking alcohol—even in moderate amounts—can negatively impact your brain.

In a landmark 30-year study, people who drank moderately (just one drink per day for women and two for men) had increased amounts of hippocampal shrinkage—literally killing parts of their brains! Unsurprisingly, heavy drinkers had more brain shrinkage (six times the amount compared to non-drinkers), but the moderate drinkers still had three times greater odds of hippocampal loss. 

Higher alcohol use was also linked to a faster decline in lexical fluency tests (the ability to name as many words beginning with a specific letter as possible within a minute) and changes in the structure of the corpus callosum—a bundle of nerve fibers that connects the brain’s two hemispheres and facilitates higher-level neurological functions. 

Another study looked at neuroimaging data of over 36,000 adults in the UK, finding that moderate alcohol intake was associated with reductions in global brain volume measures, regional gray matter volumes, and white matter microstructure. Although it may not be realistic for you to eliminate alcohol, reducing your overall intake—and striving for more dry days per week than not—can help to protect your brain over time. 

Brain Killer #4: Not Enough Sunlight

A lack of exposure to natural sunlight can be a brain killer for several reasons. We know that sunlight affects mood drastically, which also plays a role in cognitive function. Sunlight is the best natural source of vitamin D, which is vital for both cognition and mood. Studies show that insufficient vitamin D levels are linked to an increased risk of neurodegenerative and mood-related conditions, while higher vitamin D status is associated with improved cognitive function.

Natural light also regulates our circadian rhythms, influencing hormone production and healthy sleep cycles, and stimulates serotonin production—our “happy” neurotransmitter. Exposing your eyes to natural light in the morning (even if it’s cloudy) can also help to regulate your sleep, which we know is also linked to cognition and brain health. 

One study found that people with mood disorders who had lower sunlight exposure were 258% more likely to have an impaired cognitive status compared to those who saw plenty of natural light. 

Some research even indicates that sunlight exposure can boost neuroplasticity—the brain’s ability to rewire itself by forming new neural connections—an essential component of maintaining strong cognitive function with age. Light has also been found to affect brain blood flow, and insufficient cerebral blood flow can increase the risk of cognitive disorders. 

Brain Killer #5: Chronic Stress

While everyone experiences some stress every once in a while, chronic stress can be considered a brain killer. Prolonged stress can lead to hippocampal damage, neuroinflammation, and mood disorders, which can further damage brain health. 

In research with over 6,200 adults, people with higher levels of perceived stress had lower present-day cognitive scores, as well as a faster rate of future cognitive decline over the 7-year study.

One reason why chronic stress damages the brain is due to prolonged cortisol elevation. While cortisol, our primary stress hormone, is beneficial in small doses, long-term high cortisol can cause neuronal cell loss and atrophy of the hippocampus, amygdala, and frontal lobe. Stress can also prevent neuroplasticity, reducing the brain's ability to form and strengthen connections between neurons.

 

Brain Killer #6: Sitting Too Much 

A sedentary lifestyle is detrimental in many ways, both to our physical and mental health. Sitting too much—typically defined as more than 8 hours per day—is associated with reduced brain volumes and worse cognitive function in children and adults.

Being sedentary for long periods impairs glycemic control and cerebral blood flow, which reduces cognitive performance because fewer nutrients and oxygen are delivered to the brain. Physical activity is one of the best ways to boost BDNF activity, leading to neurogenesis—the growth of new brain cells. 

Sitting too much can also impact your brain indirectly by causing poor sleep and increasing the risk of mental health, cardiovascular, or metabolic conditions, which are associated with cognitive decline. 

Brain Killer #7: Loneliness 

Loneliness is becoming more and more of a public health concern, especially in older adults. Newer research has indicated that people who are socially isolated or lonely have an increased risk of mood disorders and cognitive loss. 

In a meta-analysis involving over 30,000 older adults, loneliness was significantly linked to worse cognitive function. Specifically, lonely adults had poorer global cognition, episodic memory, working memory, visuospatial function, processing speed, and semantic verbal fluency.

In animal studies, social isolation reduces neurogenesis and neural plasticity, while resocializing can reverse the effects, improving memory and increasing neuron growth.

Loneliness impacts the brain by increasing cortisol levels and the risk of mood disorders, both of which negatively affect cognition. Building or maintaining social connections, whether through friendships, family, or community activities, can help to improve loneliness, provide emotional support, reduce stress, and positively impact brain health.   

Key Takeaways

There are many brain killers out on the loose, including ultra-processed foods, alcohol, not getting enough sleep (or too much sleep) or natural light, chronic stress, sedentary lifestyles, and loneliness. To learn how to fight back against these brain killers and improve your cognitive health, check out this article about nine ways to transform your brain for the better.

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