It always makes Caveman Doctor curious as to why some people like to stay up so late, especially when they have a full day of work awaiting them in the morning, knowing well that withholding their rest will keep them dragging all day. He also absolutely loves it when the sun sets and he knows it is bedtime. Plus, once it gets dark, he becomes so tired that even the orange flame from his torchlight does little to keep him awake. It’s almost as if a part of his brain is triggered by darkness to secrete some chemical that makes him sleepy. He loves sleeping so much that he is unsure why anyone would delay such gratification. Caveman Doctor is clearly forgetting all the times he stayed up late dancing. However, few people are as good a dancer as Caveman Doctor, so he is still confused as to why everyone else would purposely stay up late.
Melatonin is a hormone produced by the pineal gland, which is a small area of the brain that secretes high levels of melatonin during the night and minimal amounts during the day. This reverse solar panel of our brain shuts off when light hits our eyes. This is caused by the retina (the back of the eye), which sends a signal to shut off a part of the brain called the suprachiasmatic nuclei (SCN), that sits in the anterior hypothalamus stimulating the pineal gland. At night, however, the SCN fires repeatedly as it is uninterrupted by light bulbs, computer screens, phones, etc. This results in a nocturnal stimulation of melatonin secretion from the pineal gland as part of the circadian rhythm1. The release of melatonin has a trancelike effect on us, allowing our brain to tell our body that it’s time to rest2, recharge, and rebuild (and a couple of other things as well as you’ll see below).
However, once the eye and retina encounter light, this signal is discontinued, and melatonin secretion stops. In fact, studies in humans have shown that when placed in an artificial “winters” with only 10 hours of daylight or an artificial “summer” with 16 hours of light, subjects sleep longer and release significantly more melatonin during the extended darkness3. Basically the darker it is and the more you sleep, the more melatonin your pineal gland secretes.
Why does it matter?
While every function of melatonin remains unknown, it has many important roles within our body:
- It is an antioxidant, scavenging free radical damage and helping to fight daily damage, wear, and tear that can lead to cancer.4
- It upregulates the immune system to fight inflammation and pathogens.
- Reduced levels of melatonin leads to an increase in estrogen5, which is the bane of all evil in many ways, but especially when it comes to cancer.
- It inhibits several pro-cancer pathways6 that are also inhibited through the induction of autophagy from intermittent fasting and ketosis.
- May reduce cellular uptake of the inflammatory omega-6 linoleic acid, found heavily in the standard American diet and vegetable oils.6
- May actually reduce cancer death in randomized controlled cancer trials.7,8
Preclinical Data/Hypothesis Generation:
Throughout science, hypotheses are often generated by animal and observational studies, and sleep is no different. Animal studies with melatonin have been going on for decades.
Scientists in the 1980s took mice and gave them DMBA, a cancer-causing chemical often used in animal experiments to induce malignant progression of cells. It is much more damaging than other carcinogens that we encounter in our environment like BPA, naphthalene, and many chemicals in plastic and serves as a good experimental carcinogen. When mice were given DMBA, nearly 80% developed breast tumors, while only 20% of those treated with melatonin develop cancer9. Interestingly, when scientists removed the pineal gland (the source of melatonin), it brought the cancer incidence right back up to 88%, illustrating the strong anticancer effect of melatonin.
Data in human breast cancer cell lines has shown similar results. Studies with MCF-7 breast cancer lines reveal a striking antiproliferative effect of melatonin on the cells10 and even suppression of the estrogen receptor gene.11 Much like a caveman after an 18 hour fast and a good, dark night sleep, the same study showed that in the presence of melatonin, the cancer cells underwent autophagy. The same study also showed that while the cancer cell growth was inhibited, normal cells were unaffected by the melatonin – showing that it may selectively target cancer cells.
Is there any evidence? Does this correlate to humans, or is it just more animal studies?
Cancer in the Blind – Constitutive Pineal Activation
In most cases, blind individuals who are unable to perceive light do not experience the inhibition of melatonin secretion like those of us with functional vision.12 A study from Stockholm, Sweden analyzed a cohort of totally blind individuals and persons with visual impairment. These two cohorts were compared because while both have severe (or total) visual impairment, only the totally blind group is known to have continued melatonin secretion, even in the presence of light, as there is no way for the signal to turn off the pineal gland. Their findings were more alarming than the buzz of an alarm clock at 5 am, shutting off your pineal gland. When analyzing the number of expected cancer diagnoses, the totally blind cohort experienced a 31% decrease in all cancers, a 33% decrease in cancers excluding breast and prostate, and a 31% decrease in cancers unrelated to smoking. All of these differences were statistically significant.
While a first inclination may be that perhaps this group does not encounter many of the cancer causing agents of our environment, is less stressed, is less in harm’s way, etc. However, the severely visually impaired group likely experiences similar lifestyle issues due to their impairment, yet their cancer rates were similar to the rest of us.
Other data has also shown an inverse association between degree of visual impairment and breast cancer13, i.e. the more visually impaired one is, the less they develop breast cancer. This data is no proof of melatonin’s effect, but thought-provoking nonetheless.
Melatonin in Breast Cancer Patients
Another study assessed 35 women with breast cancer and 28 patients with benign breast disease and compared them to age-matched controls.14 Circadian rhythms were evaluated in the groups, along with melatonin surges. Overall, the authors found a 50% decrease in peak and amplitude in the group with breast cancer, and therefore a decrease in melatonin production. Even more remarkable, this peak in circadian rhythm and nocturnal concentrations of melatonin decreased as the patients’ tumor size and stage of breast cancer increased. In other words, the more melatonin secretion was inhibited during circadian rhythm, the worse stage of breast cancer these women experienced.
A similar study revealed decreased urinary secretion of melatonin in breast cancer patients.15 It appears that not only does appropriate sleep fight cancer through melatonin production, but cancer cells may also know this as well and inhibit the secretion of melatonin from the pineal gland as a survival mechanism.
Other data has shown a connection between decreased nighttime melatonin levels and estrogen receptor positive breast cancer16, which is no surprise as low melatonin leads to an increase in serum estrogen. Interestingly, Tamoxifen, an estrogen receptor blocker and a treatment modality for breast cancer may actually stimulate melatonin secretion.14
Lack of Sleep, Cancer, and Health Risk
Many studies have been performed in night shift workers. Night shift work of as little as three nights per month is associated with a higher rate of cancer17, and this risk increases with increasing shiftwork.18 However, the risks do not end with breast cancer. Shift workers involve serious disruption of their circadian rhythm and secretion of melatonin and experience increased rates of anxiety, depression, chronic fatigue, colitis and ulcers, and cardiovascular disease.19 Other studies have shown working nights increases the risk of colorectal cancer.20 Even jet lagging mice has been shown to cause cancer from disruption of circadian rhythm.21
How Long Should We Sleep to Beat Cancer?
To answer this question we turn to Japan, where breast cancer rates have risen from 28.3 per 100,000 people in 1991 to 39.5 per 100,000 in 2001.22 Japanese researchers observed the sleep duration of nearly 24,000 women, categorizing them into four sleep groups: less than 6 hours, 7 hours, 8 hours, and greater than 9 hours. Granted, during this time they have increasingly eaten a western diet23, a huge risk for cancer. They also undertook serious statistical manipulation to account for the differences between the groups. For example, those that slept over 9 hours were generally older, ate less, and were less educated. The authors basically found that the longer one slept, the less chance she had of getting breast cancer, with women who slept 6 hours or less having 1.6 times the risk of getting breast cancer.
A similar study from Finland with 12,222 women echoed these findings, revealing the greatest avoidance of breast cancer in those that slept 9 hours, versus 7-8 and 6 hours24. Another study from Singapore looked at less than 6 hours of sleep versus 9 and revealed a significant difference in breast cancer25, favoring the heavy sleepers. The odd woman out was a similar study analyzing the infamous Nurses’ Health Study database revealed no association between sleep and breast cancer.26 However, many studies and results from the Nurses’ Health Study have been less than applicable, so it is difficult to draw conclusions.
How Should We Sleep to Beat Cancer
Keep in mind it is not only sleep that provides your endogenous melatonin production and secretion, but darkness. If you were to sleep 9 hours, but are woken up 4 times by a bright light during the sleep, your suprachiasmatic nuclei will be shut off along with its stimulation of the pineal gland. While we know from the data presented above that light will shut off the pineal gland, it appears that electric power and electromagnetic fields can disturb the circadian rhythm and shut off our melatonin production.27
More than Just Light
Different light sources have different effects on melatonin production. As expected, bright light is worse than dim light.28 The color of light appears to be of importance, with red and orange light having small to no effect, while blue-green light has a maximal effect29. Even eye color matters as data shows those with light-colored eyes more sensitive to melatonin shutoff from light.30 Yet, many alarm clocks have a bright blue glow, likely shutting off the pineal gland with a glance at the alarm clock in the middle of the night.
However, it appears that more than just light shuts off your pineal gland. 60-Hz electrical fields can shut off pineal production of melatonin.31 Even applying a magnetic field to rats decreased their melatonin production.32 This should make you think twice not only about an alarm clock, but also more so about putting a cell phone in your room or by your bed. The potential health effects are not limited to cancer, as it is hypothesized that this may lead to depression and reproductive issues as well.33
While removing all electrical devices from the bedroom may not be possible for all, there are some interesting studies like one in Oregon, which found that housewives residing in homes with electric heating had significantly higher risks of cancer34. Another study from Norway showed that household exposure in the residential setting to 50 Hz electromagnetic fields resulted in a 1.6 times an increased risk of breast cancer.35 Interestingly, the effect of electromagnetic and magnetic fields on breast cancer development is not limited to women, as another study found a significant increase in male breast cancer in male New York Telephone workers with likely high magnetic field contact.36 Another case-control study showed that electricians, power plant workers, and power line workers had six times the risk of breast cancer. These exposures are likely happening during waking hours, questioning daytime pineal disruption.37 Finally, other studies even point to alcohol as decreasing melatonin secretion in animals and humans.38,39
Many today would translate this to running out and purchasing as much factory-produced melatonin as possible.
Instead, let’s turn to the caveman for our recommendations:
- Get plenty of rest (at the very minimum 7 hours).
- Turn off any computers or televisions an hour or more before bed.
- Remove any sources of blue or white lights in your bedroom, and if you must replace them, use orange/red sources much like the flame that the caveman once used to light his bedroom.
- If you absolutely must have an alarm clock, do not get one with blue or green lighting.
- Turn your cell phone off, throw it away, or put it in another room.
- Seal off your windows with some heavy drapes to make your bedroom as cave-like as possible.
- If you use a cpap at night due to weigh-induced sleep apnea, maybe it’s time to burn that fat and ditch the humming machine all night that may be turning off your pineal gland (although this is clearly not always possible).
- Avoid alcohol before bed as it may reduce melatonin secretion.
While there is no exact right answer as to how long we should sleep, many recommend 7-8 hours of sleep per night, and this seems reasonable. Achieving at least 8 hours is likely ideal (and maybe even 9), although not always schedule permitting for most. Regardless of the amount of time you sleep, shutting off your phone, computer, or television earlier in the night will leave you with excess time to read, write, or sleep. This excess time will also allow you to go to bed earlier as the sun sets, wake up earlier with as the sun rises, just as our ancestors did for millions of years.
Also, quality of sleep is an important factor that is often overlooked. Sleep quality plays a big part in rest and melatonin secretion, and efforts to allow your pineal gland to perform its job while you sleep will only benefit your health.
Once again, good old Nature supplied us with the machinery to fight cancer; we just have to use it appropriately. Luckily, much like delicious fats, sleeping is so darn enjoyable and satisfying that it’s hard to argue against it. Get to bed early, wake up early with the sun, and sleep away cancer.
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