Most people associate the term circadian rhythm with the body’s sleep-wake pattern, which cycles about every 24 hours and is synced to the earth’s daily cycle of sunlight and darkness. Our ancestors would wake when the sun came up and get ready for sleep when it went down…and that connection bolstered their well-being.
But now we’re learning that the body’s “inner clock” does so much more…and that an out-of-whack circadian rhythm brings problems that go beyond just feeling sleepy during the day. Bottom Line Personal spoke with Lynne Peeples, author of The Inner Clock, to learn more about our circadian rhythm and how to use it to our advantage.
There is a wealth of research showing that we don’t have just one body clock. Instead, nearly every tissue and organ has its own clock, and in fact every cell in the body has its own clock. Because the body has trillions of cells, that means it has trillions of clocks that coordinate with one another. Every mechanism of our physiology—from metabolism and digestion to the immune system—runs on various clocks. Because the body can’t perform every function at every moment, these clocks direct our body to do certain things at certain times, as part of an energy-conservation system. Example: The digestive system is best prepared to break down food only at certain times of the day.
These clocks don’t work as exact timekeepers—the “circa” of circadian means “about” or “around.” But to keep things coordinated and running efficiently, they need to be calibrated to our earthly environment’s 24-hour day. We don’t function as well as we should when our circadian rhythm is out of step with nature—we know this from mounting research, including on night shift workers. The NIOSH Training for Nurses on Shift Work and Long Work Hours warns that not living in accordance with regular day-and-night patterns puts these workers at risk for a circadian rhythm sleep disorder, also known as a sleep-wake cycle disorder. This condition develops when people are unable to follow a healthy sleep-wake pattern. Symptoms may include insomnia, difficulty concentrating and depression. Research done at Washington University School of Medicine in Saint Louis shows that this disorder can be the catalyst for many chronic diseases and has been linked to accelerated neurodegeneration. Even minor disruptions in circadian rhythm can cause problems for just about anyone, including difficulty sleeping, poor quality sleep and lacking the energy for daily activities.
Depending on the season of the year and an individual’s rhythms, around dusk our circadian system prompts the brain’s pineal gland to begin releasing melatonin, the hormone that tells the body it’s time for rest. But modern life works against this natural process. In fact, the biggest affront to our inner clock is our indoor, high-tech, 24/7 lifestyle. Our bodies didn’t evolve to expect light at night, especially the blue light coming from the screens of our devices. In effect, we’ve loosened our link to the earth and the sun’s natural rhythms.
The second most impactful affront is our ability to eat around the clock. Half of all American adults eat, snack and nibble across at least 14 hours each day (and for some, as many as 20 hours!), often well into the evening. Why this is a problem: Our body temperature naturally dips a degree or two at night, which promotes sleep. But eating late prompts your body to send blood to your gut, raising your core body temperature. It can take two or three hours for the stomach to empty after eating, even longer after larger or fattier meals, and that delays the sleep process. Snacking at midnight by the light of an open fridge presents a double whammy, giving the body food when it’s not expected…and exposing it to light at the wrong time.
Also, many widely used drugs, such as metformin (for diabetes), rapamycin (for cancer), anti-tumor treatments, beta-blockers, antidepressants and possibly oral contraceptives, can negatively affect our circadian rhythms directly or indirectly. Of course, caffeine and alcohol—which bookend the day for a lot of people—also can make it harder for the body to decipher the day’s beginning from the end.
Recent research from multiple institutions including Johns Hopkins University suggests that environmental contaminants known to play havoc with our health—heavy metals, particulate matter, ozone pollution, cigarette smoke, PCBs, solvents, bisphenol-A and cyanobacterial toxins, to name a few—are probable circadian rhythm and sleep disruptors.
As we gain a better understanding of circadian science, we’re finding ways to lessen the damage from modern life and realign our bodies’ circadian rhythms. Lifestyle changes can be the most impactful…
Of course, you want to balance this with what’s practical for your lifestyle. Examples: If evening hours are your ideal time to phone friends and family, dim the screen on your smartphone…or if you must catch up on work, use programs that block blue light from your computer screen such as f.lux and Night Shift.
Here are more specifics that will also help the reset…
Some people are naturally early birds, while others are night owls. Scientists recommend that we listen to and understand our individual body rhythms and tailor our sleep schedule as much as possible to the hours our body is inclined to rest. One way to find your natural sleep and wake times: Go to bed when you’re tired, regardless of what the clock says, and wake up on your own without an alarm. Try to set your daily schedule in a way that matches your sleep type yet also maximizes light and dark.
You’ve likely heard the advice to keep your bedroom cool. Thanks to research done at Harvard, University of Southern California and Medical University of Vienna, we now believe that the ideal room temperature for sleep, at least for adults, is in the mid-60s. Keep all electronics out of the bedroom, and get an orange or other warm-colored nightlight for nocturnal bathroom trips so that you don’t need to flip on a light.
Try to get outside for an early morning walk in the sunshine. Later, enjoy a stroll outside to break up your day. Also try to spend your indoor hours close to a window.
A growing area of circadian research at the Salk Institute for Biological Studies and elsewhere is focused on time-restricted eating. Try to keep meals and snacks within a 12- or even 10-hour time frame. That is a powerful way to right our clocks and improve our health, and it is on par with switching off lights at night. Important: A healthy diet and consistent mealtimes paired with the right exposures to light and dark also could benefit the diversity of our gut microbiome and improve overall health, according to a study done at University of Pennsylvania.
Pay attention during the day to when you feel most energized physically—that’s a great time to exercise. A recent study at University of Florida and published in Journal of Biological Rhythms showed that exercise can realign and strengthen rhythms in skeletal muscles and perhaps even throughout the body…but try to avoid evening workouts. One study by researchers at Arizona State University and University of California San Diego found that participants who exercised at 7:00 am or between 1:00 pm and 4:00 pm significantly advanced the phase of their circadian rhythms and the onset and duration of melatonin release…whereas participants who exercised between 7:00 pm and 10:00 pm delayed their phase and rise in melatonin, potentially making it difficult to fall asleep until later at night.
Most over-the-counter medications have a specific time of day at which it is best to take them, but this is a very new area of scientific study and hasn’t yet made its way into regular clinical practice (this will hopefully be part of personalized medicine in the years to come). But it might be worth asking your doctor about any timing indications he/she is aware of—some prescription meds may work better or be safer for you at certain times.
You needn’t aim for perfection with these changes, but try to be consistent and make incremental changes. With time and effort, they will become positive habits.
