A new study found that daylight boosts your immune system by helping infection-fighting cells (neutrophils) work more effectively during the day.
Researchers found that your immune cells have their own internal clocks that respond directly to light — making them stronger at killing bacteria in daylight hours.
Disrupted sleep or limited light exposure (like shift work or jet lag) may weaken your immune defense, suggesting light plays a bigger role in health than we thought.
Ever wondered if daylight does more than just lift our mood?
Scientists from the University of Auckland asked that same question — and found interesting results: daylight can supercharge a key player in our immune system.
The findings from a recent study revealed that our most common infection-fighting white blood cells — neutrophils — have their own tiny clock inside them. That clock is primed by exposure to light, making them more effective at battling bacteria during the day.
“Given that neutrophils are the first immune cells to be recruited to sites of inflammation, our discovery has very broad implications for therapeutic benefit in many inflammatory diseases,” researcher Christopher Hall said in a news release.
“This finding paves the way for development of drugs that target the circadian clock in neutrophils to boost their ability to fight infections.”
How did the researchers test it?
The team turned to zebrafish – small, semi-transparent fish that allow scientists to see what’s happening inside. The researchers used zebrafish because their immune systems are similar to ours, and their see-through bodies make it easy to watch live cells in action.
They infected the fish at different times — day versus night — and measured how fast neutrophils killed bacteria. The team also tweaked key “clock” genes inside those neutrophils to see how they affected the ability to kill bacteria.
The results
Here’s what the researchers found:
Neutrophils kill bacteria better during daylight. Infected fish handled daytime infections more efficiently than nighttime ones.
The cells’ internal clocks are light-sensitive. They don't just passively follow the body's master clock in our brain—they tick inside each neutrophil, responding directly to light.
Lights-off? Neutrophils aren’t working at full strength. Less daylight or disrupted circadian rhythms could dull your immune defense—explaining why jet lag and shift work can make you more vulnerable.
Real-world applications
These findings are important for consumers because of the real-world implications on our immune systems.
Light matters—not just for sleep or mood. It directly influences how your immune system responds to infections.
Daylight exposure might help keep you healthier. Especially if your lifestyle disrupts your natural rhythms (think night shifts, late nights).
Future treatments could be time-based. Imagine medications or therapies that align with your immune system’s “active hours.” This could lead to better outcomes by boosting immune cells just when they’re most ready to fight.