Melatonin Regulates Our Cycles, Mood, Reproduction, Weight and Even Cancer

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Editor's note: Melatonin is available as a dietary supplement. Alternatively, you may also take tryptophan, an amino acid or a dietary supplement call 5-hydroxytryptophan or 5-HTP. In the body, tryptophan is converted into 5-hydroxytryptophan, which is in turn converted into melatonin.

By Dr. Mercola

Melatonin is a hormone your body produces at night, and one of its primary roles is to help you sleep. But this benefit, for which it is arguably most widely known, is only one of many.

Did you know, for instance, that melatonin may help protect against heart disease, diabetes, Alzheimer’s and migraine headaches? Or that it may help with weight control and strengthening your immune system? It even appears to play a role in cancer prevention.

Yet, because artificial lighting disrupts your melatonin production, many Americans may be lacking in this veritable ‘wonder hormone.’

Melatonin Combats Inflammation, Offers Mood and Anti-Aging Brain Support

Melatonin is a powerful antioxidant and free radical scavenger that helps ‘cool down’ excess inflammation. In fact, melatonin is so integral to the health of your immune system that a lack of it causes your thymus gland, a key component of your immune system, to shrink in size.1

Because melatonin is a strong antioxidant and is able to cross the blood-brain barrier, it is thought to help protect against Alzheimer’s disease as well as brain aging. 

In one study, artificially aged mice treated with melatonin had reduced oxidative stress and markers of cerebral aging and neurodegeneration, indicating the melatonin offered both neuroprotective and anti-aging effects.2

In another study, researchers revealed that combining daily exercise with the daily intake of melatonin appeared to have a synergistic effect against brain deterioration in mice with Alzheimer's disease-associated mutations.3Improvements in behavior, learning and memory were noted.

Melatonin's immediate precursor is the neurotransmitter serotonin, which is a major player in regulating and giving a lift to your mood. And, like serotonin, melatonin plays important roles in your physical and mental health. Studies have shown that insufficient melatonin production can set you up for:

Decreased immune function Accelerated cancer cell proliferation and tumor growth (including leukemia)
Blood pressure instability Decreased free radical scavenging
Increased plaques in the brain, like those seen with Alzheimer's disease Increased risk of osteoporosis
Diabetic microangiopathy (capillary damage) Depression and/or seasonal affective disorder (SAD)

Melatonin’s Impressive Role in Fighting Cancer

Peer-reviewed and published research has shown melatonin offers particularly strong protection against reproductive cancers. Cells throughout your body — even cancer cells — have melatonin receptors. 

So when melatonin makes its nightly rounds (its production peaks during the night), cell division slows. When this hormone latches onto a breast cancer cell, it has been found to counteract estrogen’s tendency to stimulate cell growth.

In fact, melatonin has a calming effect on several reproductive hormones, which may explain why it seems to protect against sex hormone-driven cancers, including ovarian, endometrial, breast, prostate and testicular cancers. GreenMedInfo lists 20 studies demonstrating exactly how melatonin exerts its protective effects against breast cancer.4

But melatonin’s anti-cancer effects don’t stop there. While causing cancer cells to self-destruct, melatonin also boosts your production of immune-optimizing substances such as interleukin-2, which helps identify and attack the mutated cells that lead to malignant cancer. 

Through these dual actions, melatonin delivers a one-two punch! 
The greatest area of melatonin research to date has to do with breast cancer. Some of the more impressive studies include the following:

  • The journal Epidemiology5 reported increased breast cancer risk among women who work predominantly night shifts
  • Women who live in neighborhoods with large amounts of nighttime illumination are more likely to get breast cancer than those who live in areas where nocturnal darkness prevails, according to an Israeli study6
  • From participants in the Nurses’ Health Study, it was found that nurses who work nights had 36 percent higher rates of breast cancer7
  • Blind women, whose eyes cannot detect light and so have robust production of melatonin, have lower-than-average breast cancer rates8
  • When the body of epidemiological studies are considered in their totality, women who work night shift are found to have breast cancer rates 60 percent above normal, even when other factors such as differences in diet are accounted for9

Can Melatonin Help You Fight Fat?

A new study by Spanish scientists suggests that reducing unhealthy weight gain can now be added to melatonin’s impressive roster of benefits. They found that consuming melatonin stimulates the appearance of ‘beige’ fat, which, similar to brown fat, is a heat-generating type of fat that helps your body to burn calories rather than store them. This, the researchers believe, may explain why melatonin helps control body weight, along with its metabolic benefits.

Science Daily reported:10

The study… showed that chronic administration of melatonin sensitizes the thermogenic effect of exposure to cold, heightens the thermogenic effect of exercise and, therefore, constitutes excellent therapy against obesity. 

The fact is that one of the key differences between 'beige fat,' which appears when administering melatonin, and 'white fat,' is that 'beige fat' cell mitochondria express levels of UCP1 protein, responsible for burning calories and generating heat.”

Though this wasn’t discussed in the study, it’s also well proven that lack of sleep is linked to obesity, while if you're not getting enough sleep, there's a good chance your melatonin production is not up to par either. The disturbance to your melatonin levels caused by lack of sleep may be one more reason why it leads to weight gain, and this could have far-reaching impacts on your health.

Help for Heart Disease, Headaches, Diabetes and Osteoporosis?

Newer areas of research surrounding melatonin include its role in heart and bone health. Specifically, research suggests it may have beneficial effects for heart disease, including reducing the severity of high blood pressure, limiting the frequency of heart failure and protecting against drug-related damage to the heart.11Also noteworthy, research has shown that taking melatonin before bed reduced the frequency of migraine headaches by half (or more) after three months,12 as well as may be useful for restoring imbalances in bone remodeling to prevent bone loss.13 Finally, recent research showed that people who secrete lower levels of melatonin have double the risk of developing type 2 diabetes compared to those with the highest levels,14 suggesting a protective role for the hormone with this disease as well.

If You Turn On a Light at Night, You’re Stopping Your Melatonin Production

Given its myriad of invaluable benefits, you certainly want to do all you can to protect your body’s natural production of this hormone. In humans as with all mammals, your biological clock resides in the suprachiasmatic nucleus of your brain (SCN), which is part of your hypothalamus. Based on signals of light and darkness, your SCN tells your pineal gland when it’s time to secrete melatonin. Light comes in through your eyes and travels up your optic nerves to the SCN, which is exquisitely sensitive to cycles of light and darkness.

When you turn on a light at night, you immediately send your brain misinformation about the light-dark cycle. The only thing your brain interprets light to be is day. Believing daytime has arrived, your biological clock instructs your pineal gland to immediately cease its production of melatonin. Whether you have the light on for an hour or for just a second, the effect is the same — and your melatonin pump doesn’t turn back on when you flip the light back off.

Since humans evolved in the glow of firelight, the yellow, orange and red wavelengths don’t suppress melatonin production the way white and blue wavelengths do. In fact, the range of light that inhibits melatonin is fairly narrow — 460 to 480 nm. If you want to protect your melatonin, when the sun goes down you would shift to a low-wattage bulb with yellow, orange or red light. Dr. Russel Reiter suggests using a salt lamp illuminated by a 5-watt bulb in this color range.

How to Improve and Protect Your Melatonin Production

If you’re wondering how to ensure that you’re getting enough melatonin, supplementation may be beneficial but it is FAR more beneficial and certainly less expensive to have your body produce its own melatonin. Small quantities are also found in foods like Goji berries, almonds, sunflower seeds, coriander and cherries, but, again, when you optimize your own production you will get the “perfect” dose of melatonin for you. The way to do this is to improve your sleep hygiene, which will in turn help you optimize your melatonin production. For a comprehensive sleep guide, please see my article 33 Secrets to a Good Night's Sleep.

  • Avoid watching TV or using your computer in the evening, at least an hour or so before going to bed. These devices emit blue light, which tricks your brain into thinking it’s still daytime. Normally, your brain starts secreting melatonin between 9 pm and 10 pm, and these devices emit light that may stifle that process.
  • Make sure you get BRIGHT sun exposure regularly. Your pineal gland produces melatonin roughly in approximation to the contrast of bright sun exposure in the day and complete darkness at night. If you are in darkness all day long, it can’t appreciate the difference and will not optimize your melatonin production.
  • Sleep in complete darkness, or as close to it as possible. Even the slightest bit of light in your bedroom can disrupt your biological clock and your pineal gland's melatonin production. Even the tiniest glow from your clock radio could be interfering with your sleep, so cover your clock radio up at night or get rid of it altogether. Move all electrical devices at least three feet away from your bed. You may want to cover your windows with drapes or blackout shades, or wear an eye mask when you sleep.
  • Install a low-wattage yellow, orange or red light bulb if you need a source of light for navigation at night. Light inthese bandwidths does not shut down melatonin production in the way that white and blue bandwidth light does. Salt lamps are handy for this purpose.
  • Keep the temperature in your bedroom no higher than 70 degrees F. Many people keep their homes too warm (particularly their upstairs bedrooms). Studies show that the optimal room temperature for sleep is between 60 to 68 degrees F.
  • Take a hot bath 90 to 120 minutes before bedtime. This increases your core body temperature, and when you get out of the bath it abruptly drops, signaling your body that you are ready to sleep.
  • Avoid using loud alarm clocks. Being jolted awake each morning can be very stressful. If you are regularly getting enough sleep, you might not even need an alarm.
  • Get some sun in the morning, if possible. Your circadian system needs bright light to reset itself. Ten to 15 minutes of morning sunlight will send a strong message to your internal clock that day has arrived, making it less likely to be confused by weaker light signals during the night. More sunlight exposure is required as you age.
  • Be mindful of electromagnetic fields in your bedroom. EMFs can disrupt your pineal gland and its melatonin production, and may have other negative biological effects as well. A gauss meter is required if you want to measureEMF levels in various areas of your home.

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