Body Clock and Cancer
A Cancer Survival Journey

Time Change Alert—What’s the Link Between Body Clock and Cancer?

+ Pamela Friedman

Is there a link between body clock and cancer?

Most of us recently went through our second time change of the year, when we “fell back” an hour to allow standard time to resume.

This change marked the end of daylight saving time, which won’t start again until March next year.

The fall time change is usually a little more welcome than the spring one since we all get an extra hour of sleep. But if you’re not feeling particularly rested—or if you may be feeling more tired than usual—don’t worry. You’re not alone.

Each time you go through these time changes, you disrupt your normal body clock. And doing that too often, according to scientists, may increase your risk for some types of cancer.

The good news is that the opposite—working with your natural body clock—may help reduce your risk of cancer. In this post, we examine both sides of this issue and show you how you can take advantage of the research to stay as healthy as you can.

Body Clock and Cancer—What is the Body Clock?

Also called the “circadian rhythm” or “biological clock,” the body clock refers to the internal cycles that your body goes through in a 24-hour period. They’re the natural physical, mental, and behavioral changes that occur every day, usually in response to daylight and nighttime.

Your body clock is composed of specific molecules (proteins) that interact with cells throughout the body. You have an overall master clock, but each organ and group of tissues also has its own clocks.

Every morning, your eyes take in the sunlight, which sends signals to your brain. These signals help your body wake up and get going for the day. Throughout the day, the master clock in the brain sends signals to the rest of the brain and body to help keep you awake and sustain your energy.

At night, when the daylight naturally fades, it triggers the release of hormones that help you slow down, feel drowsy, and eventually, fall asleep.

Your internal body clock keeps many of your body’s functions going on a schedule. It’s why you tend to feel hungry at regular times, why you like to exercise at certain times over others, and why you get tired at certain times.

What Determines the Schedule of the Body Clock?

Each of us is born with our own, unique body clock. Our genes affect the settings of that clock, including when we feel the most energy when we naturally go to sleep and wake up, what our normal blood pressure is, and even our typical mood.

If left to our own devices—without anything else determining our schedules—we’d likely follow this internal clock each day, allowing it to determine when we go to sleep and wake up, when we eat, and when we exercise.

This is why some people are what we call “night owls”—they have a later body clock—while others are “morning larks.” Some people land right in the middle. You likely know where you naturally gravitate when it comes to the times of day you’re likely to feel more energetic or sleepy.

The environment around us, though, can also have a big impact on the body clock. If your job requires you to do shift work, for example, you will have to disrupt your normal body clock to work when you’d usually sleep and then sleep during the day.

These types of disruptions over time may negatively affect our health.

Age, as well, can affect our circadian rhythms. Whereas teenagers may need a later wake time, older adults often have a harder time falling asleep and wake up earlier in the morning.

Body Clock and Cancer—How Does the Body Clock Affect Health?

Our master clock influences important functions in our bodies including the release of hormones, eating habits, digestion, sleep, metabolism, and body temperature. It affects the strength of our immune system, appetite, and mood. Scientists have found that our circadian rhythms influence mental health as well.

We know this because we’ve seen the effects of disrupting the body clock. You already know that if your regular sleep schedule is disrupted all week long, you’re going to not only feel tired and irritable, but you are also likely to eat more than normal, gain weight, and lose energy.

If you’ve ever had to do shift work, you also know how your body can flounder trying to recover from the disruption. Your brain isn’t getting the light exposure that it needs when you wake up, so your hormones go out of whack and you feel like you’re experiencing jet lag.

Today’s “always-on” society can also greatly affect our circadian rhythms and our health. Working too late under artificial lights can confuse your brain about when it’s daylight and when it’s night. Exposure to light at late hours can cause your brain to release “waking” hormones that then make it more difficult for you to get to sleep, leaving you sleepy the next day.

Your eating habits, too, can affect your inner body clock. If you eat too late—dinner at a late hour or a late-night snack—it revs up your digestive system when it’s used to slowing down. That can keep you awake, affecting your sleep. The next day, you’re tired and sluggish and may be carrying around more weight.

Body Clock and Cancer—How They’re Related

Scientists already know that long-term shifts to the internal body clock can increase the risk of cancer. That’s because their studies of shift workers show that they are more at risk for the disease.

A recent report from the National Toxicology Program (NTP) showed a persistent relationship between shift work and cancer risk. “In the NTP report,” the Centers for Disease Control and Prevention (CDC) stated, “it was concluded that there is ‘high confidence’ that persistent night shift work that results in circadian disruption can cause human cancer.”

The International Agency for Research on Cancer (IARC) has gone so far as to conclude that night shift work is “probably carcinogenic to humans,” based on evidence from human studies of breast and prostate cancer and research into the mechanisms of how cancer develops.

One of the problems is that disruption to the body clock can harm the systems we have in our bodies that help prevent cancer. Melatonin, for instance—the sleep hormone—not only helps us fall asleep but also helps stop tumor growth and protect against the spread of cancer cells.

When we disrupt our normal sleep rhythms by working the late shift or continuing to expose ourselves to lights (including computer, tablet, and phone lights) late at night, we reduce the release of melatonin.

That not only makes it harder to fall asleep but also robs the body of melatonin’s protective effects.

There are other mechanisms as well that increase cancer risk. Circadian disruption affects the chemical reactions that produce energy in the body. It tampers with the immune system and compromises DNA repair in cells.

And it’s not only cancer that we have to worry about. Regular body clock disruption has also been tied to the following health issues:

Body Clock and Cancer—What You Can Do

New research shows that targeting the body’s biological clock may help treat cancer. According to a 2018 study, two compounds that target components of the circadian clock killed several types of cancer cells and slowed the growth of brain tumors.

Research has also found that certain chemotherapy treatments are more effective when given in accordance with the patient’s natural body clock rhythms.

Meanwhile, what we all want to do is prevent cancer from occurring in the first place. To keep your body clock on track and reduce your risk of disease, follow these tips:

  • Maintain a consistent sleep schedule: Go to bed and get up at the same times every day, even on the weekends.
  • Avoid exposure to light at night. At least an hour before bed, turn down the lights and turn off the technological gadgets, including your phone, computer, and television. Do something quiet and relaxing like taking a hot bath, reading, or listening to calming music.
  • Get outside in the morning. Exposing yourself to bright light in the morning is key to jumpstarting your normal circadian rhythm. Natural sunlight is ideal. On cloudy days, try a sun lamp. Then place your workstation near a window if you can.
  • Avoid eating late at night. Stop eating at least two hours before bed. If you get a craving, try drinking a tall glass of water or a hot cup of tea.
  • Exercise regularly. Daily exercise can keep all your body systems on track. It can also help prevent cancer on its own.
  • Watch your caffeine intake. Individuals differ in their ability to metabolize caffeine. If you’re having trouble sleeping, avoid caffeine after noon.
  • Create a comfortable sleep atmosphere. This means a dark, cool room and a comfortable mattress.

Do you struggle to maintain your normal body clock?

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