heat, hydration & the nervous system: why summer makes us lose our cool
Have you ever been stuck in traffic on a 90-degree day and suddenly wanted to fight everybody? You're not alone. As it turns out, there's real science behind why heat makes us irritable, exhausted, and frankly, a little unhinged.
In the final episode of our summer miniseries, we sat down to unpack how heat and dehydration affect the nervous system — and what we found was both fascinating and a little alarming. From road rage to neurotoxicity, here's what you need to know before your next hot day.
Heat Changes Your Mood — And It's Not Just "In Your Head"
Let's start with the obvious: heat makes us cranky. Melinda recalled finding a research prompt that asked, "Have you ever been stuck in traffic on a 90-degree day and realized you suddenly wanted to fight everybody?" The answer, for most of us, is a resounding yes.
But it's not just irritability. Heat and dehydration can make you:
Tired — Your body is working overtime to regulate temperature
Angry and frustrated — Your nervous system is under stress
Irritable — Small annoyances feel much bigger
Overwhelmed — Cognitive function takes a hit when you're dehydrated
And here's the thing: most of us don't connect these feelings to hydration. We blame the traffic, the heat, the situation — when really, our bodies are sounding an alarm.
The Science: Dehydration Makes Pain Hurt More
Dr. Paige dug into a 2014 study that examined how dehydration impacts pain perception. Here's what the researchers found:
The study involved five healthy adult men who completed a 40-minute exercise protocol after 12 hours of fasting, under two conditions: hydrated and dehydrated. After exercising, researchers applied a cold pressor test (a painful cold stimulus) to measure how each subject perceived pain.
The results were striking. Dehydrated subjects experienced significantly stronger pain responses than hydrated ones. Their bodies showed greater stress markers — higher heart rate, increased temperature, and higher urine osmolality. Even more interesting? Levels of hunger, anxiety, and mood weren't significantly different between the two groups — but pain perception was.
In other words, dehydration doesn't just make you uncomfortable. It literally amplifies how much pain you feel.
"I Want to Cry, But I Have No Water, No Tears to Cry"
Dr. Paige shared a personal story that brought the science to life. On a recent Sunday, she set out for a 14-mile training run. She started later than planned — 6:40 AM instead of 6:00 AM — which meant more sun exposure on an exposed trail.
Around mile 9 or 10, she ran out of water. The temperature had climbed from about 70°F to over 90°F. And then something alarming happened: she stopped sweating.
"I want to cry right now, but I have no water, no tears to cry. Everything hurts. If I wasn't hurting, I just want to kind of throw my body around and have a tantrum."
Her body was in full conservation mode — holding onto every drop of water it had left. The last four miles were brutal.
Fight, Flight, or Freeze: Why Your Body Freaks Out When Dehydrated
Melinda broke down what was happening physiologically. When your body is severely dehydrated, it can trigger a fight, flight, or freeze response — the same survival mechanism that kicks in when you're in actual danger.
Here's what that looks like:
Tears stop — Your body won't "waste" water on crying
Bodily functions change — Some people may involuntarily urinate as the body sheds excess weight to keep moving
Everything non-essential shuts down — Your body is in survival mode
The irony? There was no actual danger. She had simply run out of water. But the body doesn't distinguish between a predator chasing you and a dehydration crisis — it responds the same way.
And here's the critical part: it takes a long time to come down from that response. Even after the run was over, Dr. Paige wasn't hungry or thirsty for hours — her body was still in survival mode, not yet recognizing that the "danger" had passed. She described it as feeling like a hangover. Your body was fighting for its life, and you feel it everywhere.
Chronic Heat Stress: A Brain Health Crisis
This is where the conversation takes a more serious turn. Dr. Paige highlighted research connecting chronic heat exposure to long-term brain health:
Heat shock proteins — These are molecular chaperones that protect neurons from damage. But when heat stress is chronic, these protective mechanisms can become overwhelmed.
The "Alzheimer's Axis" — Researchers are exploring how acute heat stress scrambles brain networks, and what happens over years of cumulative climate-driven heat waves. The link? Chronic thermal stress may increase the risk of Alzheimer's and dementia.
Neurotoxicity — Chronic heat stress stimulates glial cells and astrocytes in ways that, over time, can be neurotoxic. As Dr. Paige put it: "Chronic thermal stress isn't just uncomfortable — it is neurotoxic."
This isn't just about feeling cranky on a hot day. Long-term, repeated exposure to high temperatures without proper hydration and recovery could have lasting effects on cognitive health.
How to Actually Stay Hydrated
So what should you do? Here are the practical guidelines Dr. Paige shared:
Know Your Baseline
Aim for half your body weight in ounces of water per day as a baseline
If you're physically active, you need to replenish everything you sweat out
Understand Your Sweat
Some people lose more sodium than others — if you're a "salty sweater" (you can taste it, or your face feels crusty after a workout), you need electrolytes, not just water
Know how much you typically sweat during different activities
Dr. Paige's Daily Hydration Routine
Morning: 15-24 oz of water
Workday: 24 oz of water with LMNT electrolytes + 30-50 oz of regular water
During exercise: Drink water throughout, and consider electrolyte supplementation
After exercise: Replenish and listen to your body
It's Okay to Rest
As Melinda reminded us: "If it feels like it's too much and you're overdoing it, it's okay to not do it that day, and to take care of yourself in another way instead."
The Bottom Line
Our bodies are mostly water. Our cells and organs depend on it. And now we know that hydration isn't just about physical comfort — it's about mood regulation, pain perception, cognitive function, and long-term brain health.
Whether you're running 14 miles or sitting in traffic on a 90-degree day, your nervous system is listening. The question is: are you listening to it?
Drink your water. Know your sweat. And if you're overdoing it in the heat — give yourself permission to stop.
