Your circadian rhythm is the invisible orchestra that controls your internal clock. It influences your sleep, digestion, metabolism and hormone production. In short, it is crucial for your health.
But more and more research shows that light at night acts like kryptonite to this delicate rhythm. Your body functions best when you get plenty of light during the day and as little as possible at night.
Almost everyone knows by now that too much light in the evening can disturb your sleep. But the consequences go much further: a new study with over 84,000 participants who were observed over eight years shows that a higher exposure to light between 1:30 am and 6:00 am is associated with a 53% increased risk of type 2 diabetes.
The interesting thing is that the scientists took into account factors such as shift work or lack of sleep, so the results cannot simply be attributed to an unhealthy lifestyle.
One key mechanism is the reduced production of melatonin. This hormone signals to your body that it is time to sleep and ensures that you enter deep, restorative sleep phases. If melatonin production is disrupted by light, not only the quality of your sleep suffers, but also your metabolic health.
Another experiment confirmed this effect: just one night under bright overhead light reduced the insulin sensitivity of healthy people by 16%. Poorer insulin sensitivity means that your body processes blood sugar less efficiently - a key risk factor for diabetes.
The good news is that you can do a lot to protect your body from the negative effects of night light.
Keep your bedroom as dark as possible: blackout curtains or sleep masks help to minimize outside light sources.
Avoid screens before sleep: Blue light from cell phones, tablets or televisions inhibits melatonin production particularly strongly.
Use warm, dimmed light in the evening: candlelight or special sleep lamps are less disruptive to your rhythm than bright artificial light.
Switch off all unnecessary light sources: Even small light sources such as standby LEDs or night lamps can affect your sleep.
Your body is designed to function in harmony with light and darkness. By reducing light at night, you help it to function optimally - and protect your health in the long term.
Cheung, I. N., et al. (2022). "Nighttime light exposure and metabolic health: A population-based study." Journal of Sleep Research.
Czeisler, C. A., et al. (2019). "Circadian rhythm disruption and its metabolic consequences." The Lancet Diabetes & Endocrinology.
Zhang, X., et al. (2023). "Impact of artificial light at night on glucose metabolism and diabetes risk." Nature Metabolism.