reseWhile expanding waistlines are what people usually imagine as a result of late night snacking, a new study out of UCLA suggests that our memories might also be at risk. The study tested what happens when eating time is disassociated from light-dark cycles. “The timing of food is a powerful signal to our brain,” said Christopher Colwell, the director for the Laboratory of Circadian and Sleep Medicine and lead author on the study. Researchers misaligned the time during which food was made available to mice, normally nocturnal creatures, forcing them to eat during the day. They monitored total sleep time, which was unaffected — both the misaligned mice and the control group slept the same total amount of time. But the misaligned mice slept more sporadically and ate during hours that would naturally be reserved for sleep.
Researchers concluded that “taking in calories at the wrong time of day … has a negative impact on your metabolism,” Colwell said, adding that the repercussions of metabolic disruption are felt right down to brain chemistry.
The protein most affected by the disruption is known as CREB, explained Cristina Ghiani, associate professor at the David Geffen School of Medicine at UCLA and an author on the paper. CREB binds to DNA, activating certain genes associated with both circadian rhythms and the pathways for learning and memory in the hippocampus. Disruptions in CREB, caused by misaligned eating schedules that disrupted the sleep-wake cycle, resulted in impaired cognitive function in the mice: They showed a decreased ability to recognize objects and a decline in long-term memory.
But Fred Turek, director of the Center for Sleep and Circadian Biology at Northwestern University, an expert in the field unaffiliated with the UCLA study, noted that the study still hasn’t teased apart which of these effects are due to the mice’s sporadic sleep patterns or their circadian misalignment. (Fragmented sleep has previously been shown to impact memory consolidation during sleep.) The effects of circadian disruption are diverse, so perhaps it’s both. Turek noted that the liver is particularly sensitive to circadian disruption, altering the feedback to the brain during meal times. Yet as far as symptoms go, the result is the same, Turek said, and the study highlights the particular effects on learning and memory.
Save the Disruption for Silicon Valley
Circadian rhythms regulate our daily lives: They’re responsible for our peak hours of productivity; they make our eyes drift shut as evening turns to darkness; they cause pangs of hunger as our metabolisms rev up for an expected meal time. But the dictums of contemporary work culture drive us to work longer, later, harder, and as a result those circadian rhythms are chronically disrupted.
The misalignment already has wide-ranging implications for the modern workforce. Though the three authors were cautious in extrapolating directly onto people, in the human body CREB serves the same purpose as in mice. It helps explain some of the health trends among shift workers — increased susceptibility to disorders that implicate CREB, a decline in cognitive ability — and offers individuals with poor habits a route for change.
The mice in the study took full meals at inappropriate times, Colwell said, adding that the effects could be mitigated simply by reaching for something a bit lighter. Dawn Hsiao-Wei Loh, a researcher with UCLA’s Laboratory of Circadian and Sleep Medicine and one of the authors of the study, added that small changes can be made to evening environments, including apps like f.lux that regulate the amount of blue light emanating from our screens. And further research could have wide-ranging clinical implications. Disorders like Huntington’s Disease, Parkinson’s Disease, and Alzheimer’s Disease have links to disrupted sleep-wake cycles, so Colwell floated a hypothesis that meal timing could be used to strengthen patients’ circadian rhythms and improve cognitive function. It’s not a cure, but it’s a useful tool when a cure is not yet available.
Until then, if the urge to snack late at night strikes you, stick to smaller portions and keep the lights down low.
