The Simple Science of Better Sleep: Light, Food, and Timing
Reconnecting Daily Rhythms to Rediscover Better Sleep
Educational only, not medical advice - See full disclaimer.
If you’ve ever found yourself awake at 3 a.m., staring at the ceiling and wondering why sleep has become so elusive, you’re not alone. For many of us over 50, sleep doesn’t come as easily as it once did. We’ve tried the apps, the supplements, and the weighted blankets. The global market for sleep aids now exceeds $100 billion annually.
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An article in Nature, published last fall (September 2025), takes a refreshing step back from sleep hacks. It looks instead at what decades of circadian science reveal about how our bodies actually function. The findings are straightforward: our internal clocks need three basic things to function well: contrast between light and dark, consolidated eating windows, and consistent sleep times. Get these right, and sleep often follows.
What the Research Shows
Over the past fifty years, scientists have mapped an intricate network of biological clocks throughout the human body. These clocks don’t just regulate sleep; they also coordinate when our immune systems fight infections, when our digestive enzymes are at their peak, and even when our bodies should heal. But the crucial part is that these clocks don’t run on their own. They require regular calibration from external cues, particularly in terms of light and food timing.
The review synthesizes multiple studies examining how modern life disrupts these natural rhythms. We spend most of our time indoors under lighting that’s far too dim during the day (typically 100-250 lux, compared to 10,000+ lux outdoors, even on overcast days). We eat late into the evening. We shift our sleep schedules between weekdays and weekends, essentially giving ourselves jet lag every week.
The consequences go well beyond feeling groggy. Short-term circadian disruption reduces cognitive function, mood, and reaction time. Long-term, the research links it to increased risks of diabetes, depression, heart disease, and even shorter life expectancy. One UK study of nearly 90,000 people found that those with the poorest light-exposure patterns were predicted to die around five years earlier than those with the healthiest habits, even after accounting for income and physical activity.
Understanding Your Body’s Light Receptors
Scientists identified specialized light-sensitive cells in the eye that aren’t involved in vision. These cells act as circadian sensors, detecting both the intensity and wavelength of light. They work alongside our retinal rods and cones, gathering information about the light environment and relaying it to the brain’s circadian pacemaker.
These sensors are remarkably tuned to blue wavelengths. When these cells detect bright blue light during the day, they synchronize circadian rhythms throughout the body and support the nightly surge of melatonin, the hormone that signals it’s time to sleep.
The same blue light can also directly boost alertness and cognitive performance during daytime hours. But when those same sensors detect bright light especially blue wavelengths at night, the circadian system gets confused. The timing of exposure matters enormously. Light in the middle of the night, when your system least expects it, is most disruptive.
Studies show that even dim light from a hallway bulb during these hours can raise heart rate and impair sleep quality.
Why This Matters More as We Age
Here’s something the research highlights that resonates particularly for those of us in our 50s, 60s, and beyond: as we age, our eye lenses naturally yellow, filtering out more of the blue wavelengths that synchronize our internal clocks.
We’re literally getting less circadian signal from the same amount of light as we age. This means that getting adequate bright light exposure during the day becomes even more critical; yet we often move in the opposite direction, spending more time indoors.
Modern building design compounds the problem. Energy codes limit the brightness of indoor fixtures. Windows, especially those with energy-efficient glass, significantly dilute the incoming daylight. Many of us also wear glasses with blue-light-blocking lens coatings designed to reduce eye strain.
The good news? The interventions that help are accessible and don’t require expensive equipment.
The Power of Contrast
The light prescription is fundamentally about contrast. Your circadian system evolved expecting bright, blue-rich daylight and near darkness at night. What confuses it most is the contrast between dim days and bright nights. The research shows that morning and daytime light exposure actually buffers against the potential harm of evening light. Your total daytime light matters more for predicting healthy sleep patterns than avoiding screens at dusk.
In fact, one study of college students found that total hours of light exposure during the day predicted bedtimes and wake times better than light exposure after dusk.
As circadian researcher Mariana Figueiro puts it: “The more light you get during the day, the better you’ll sleep at night.” Still, evening light isn’t irrelevant. A sufficient number of photons of any color at night can alter rhythms and suppress melatonin levels. A bright light in the middle of the night (like flipping on a bright bathroom light at 2 a.m.) is most disruptive when your circadian system’s sensitivity peaks.
The practical approach is to seek strong contrast: maximize bright light exposure during waking hours and minimize it after dark. This doesn’t mean living like our ancestors; it simply means being more intentional about light exposure throughout the day.
The Hidden Connection Between Food and Sleep
The food timing story is equally compelling, though less widely understood. Your liver at 10 a.m. and your liver at 10 p.m. are functionally different organs. The same is true for your pancreas, your gut, and other parts of your digestive system. Hunger hormones, digestive enzymes, and insulin all follow pronounced rhythms.
The human body is not equipped to process food efficiently at all hours. Research shows we’re most prepared for incoming calories from late morning to early afternoon. When we eat late in the evening, several problems occur. First, we disrupt the body clocks in our liver, gut, and other organs. Second, eating sends blood flow to the digestive system and raises core body temperature. Third, late meals elevate glucose levels and can uncouple peripheral clocks from the master clock in the brain, increasing the likelihood of those frustrating middle-of-the-night bathroom trips.
There’s also emerging evidence that late eating disrupts the gut microbiome in ways that may contribute to insomnia. The organisms living in our digestive tract have their own rhythms, and late-night eating disrupts their schedules.
The research suggests finishing dinner at least three hours before bedtime, ideally without consuming subsequent snacks or calorie-rich drinks. This gives your body time to complete the significant work of digestion before you attempt sleep.
What You Eat Matters Too
Beyond timing, food quality also affects sleep. Diets high in sugar and saturated fat have been shown to lighten and fragment sleep architecture. Caffeine, which many of us know disrupts sleep, lingers in the system far longer than most people realize. Its half-life can be five to six hours, meaning that late-afternoon coffee still has meaningful levels circulating at bedtime.
Alcohol presents a particularly deceptive problem. While it may help you fall asleep initially, it significantly degrades sleep quality over time. You might lose consciousness, but you won’t get the restorative sleep your body needs.
On the positive side, certain foods may actively support sleep. Research shows that walnuts boost melatonin levels and sleep quality. One study found that greater daytime intake of fruits and vegetables correlates with less fragmented sleep. The mechanisms aren’t entirely clear, but plant-based foods contain compounds that may support circadian function and melatonin production.
What This Might Mean for You
The practical takeaways are remarkably straightforward:
Get outside during daylight. Even 20-30 minutes of outdoor time in the morning or midday provides exponentially more circadian-stimulating light than indoor environments. If you can walk rather than drive for short errands, you’re getting both exercise and light exposure. Sit near windows when you can. If you work indoors all day or live in a climate with limited winter daylight, consider investing in a daylight-mimicking LED lamp for use in the morning.
Embrace darker evenings. Dim your lights after dinner. Use warmer spectrum settings on screens or apps that automatically shift color temperature as evening approaches. Consider a low-wattage amber nightlight for bathroom trips instead of overhead lights. If you do need to turn on lights at night, keep them as dim as possible and avoid the brightest overhead fixtures.
Consolidate your eating window. Think of the adage: eat like a king in the morning, a prince at noon, and a peasant at dinner. That modest dinner should finish at least three hours before bed. If evening snacking is a hard habit to break, try gradually moving your last bite earlier by 15-minute increments over several weeks.
Keep sleep times consistent. Your body thrives on predictability. Weekend sleep schedule shifts disrupt the very rhythms you’re trying to support. If you currently sleep much later on weekends, the transition to consistency may take time; your body has adapted to the current pattern, even if it’s not optimal.
Mind the quality of what you eat. Emphasize whole foods, fruits, vegetables, and healthy fats during the day. Be strategic about caffeine timing. If sleep is a concern, consider cutting off caffeine intake by early afternoon. And be honest with yourself about alcohol’s effects on your sleep quality, even if it helps you fall asleep initially.
The Balanced View
A few important caveats: Individual responses to light vary considerably, even among people of the same age. Eye color, sex, and other characteristics all play roles that scientists are still working to understand. Context also matters. If you’re doing something genuinely relaxing on a screen at 11 p.m., that might outweigh the stimulating effect of the light itself. The goal isn’t rigid perfection but instead moving your overall patterns in a healthier direction.
The Nature article also doesn’t provide the kind of randomized controlled trial that would definitively prove these interventions work for everyone. Much of the evidence comes from observational studies and mechanistic research, which show how these factors affect our biology, rather than large-scale intervention trials that prove they improve sleep outcomes across diverse populations.
The recommendations are grounded in solid circadian science; however, individual mileage may vary.
The authors acknowledge that the precise prescription is a personal matter. What works optimally for one person may need adjustment for another. Some people are naturally more sensitive to light or more flexible in their circadian rhythms.
Finally, for those struggling with significant insomnia or sleep disorders, these fundamental steps are essential but may not be sufficient on their own. A professional evaluation can identify specific issues, such as sleep apnea, restless leg syndrome, or other conditions that require targeted treatment. The circadian approach provides a foundation, but it’s not a cure-all.
A Different Way of Thinking About Sleep
What is most valuable about this circadian perspective is how it reframes the conversation about sleep. Instead of viewing sleep as an isolated problem to fix with the right pillow or supplement, it invites us to consider how the entire rhythm of our days, our light exposure, our eating patterns, and our consistency either support or undermine our body’s natural capacity for rest.
This represents a shift from treating sleep as something we do to ourselves toward understanding it as something that emerges from a well-regulated circadian system.
When we align with our biology rather than fighting against it, sleep often becomes easier without heroic interventions.
How aligned is your daily rhythm with what your circadian system seems to need?
If you interested to read more about how to evaluate and improve your sleep, I encourage you to also read my other two previously published articles on these topics:
This is an excellent “back to physiology” piece, thank you! In clinic, the biggest sleep breakthroughs rarely come from another supplement; they come from restoring circadian contrast: bright days, dim nights, plus consistent timing for sleep and food. I also appreciate you highlighting the under-recognized driver: most of us live in biologically dim daytime light (indoors) and biologically bright evenings (screens + overhead LEDs), which is essentially the perfect recipe for 3 a.m. wake-ups. The other clinically high-yield lever you emphasize (meal timing) is real: late eating can keep core temperature and glucose/insulin signaling elevated and can “pull” peripheral clocks out of sync with the brain’s clock. The practical prescription you outline (daylight early, lights low after dinner, finish dinner ~3 hours before bed, steady wake time) is simple, but it’s not simplistic; it’s how the system is built to run. And I love the tone of “aim for direction, not perfection”. For readers who do all of this and still struggle, your final point matters: that’s often when it’s worth screening for sleep apnea, restless legs, meds/alcohol effects, or mood physiology, because the foundations set the stage, but sometimes there’s a treatable blocker.
Thank you for writing this excellent piece. I just finished listening to an interview with Michael Grandner, PhD a sleep researcher at the University of Arizona (https://www.foundmyfitness.com/episodes/michael-grandner). He said a lot of the same things, including getting light throughout the day to set your sleep and wake times.
Can you share the reference to the Nature article?