If you’ve heard of melatonin, it’s probably in the context of sleep and preventing jet lag. It is often called the “sleep hormone”. But melatonin is far more than that. This series of blog posts will look at the different beneficial effects of melatonin, above and beyond its role in sleep – including it’s anti-cancer effects.
What is melatonin?
Melatonin is a hormone that is secreted by the pineal gland in the brain when the eyes do not detect light. However, it is also produced by the retina of the eye, and by the gastrointestinal system. There is actually 400 times more melatonin found in the gut than in the pineal gland or blood.
Pineal melatonin levels begin increasing in the late evening, reaching the maximum in the early morning hours around 2-4 a.m., followed by a slow decline to lower daytime levels. Daytime levels are barely detectable, as you can see in the graph below.
Gut melatonin levels also increase after eating, which might be part of the reason why we feel sleepy after a meal.
Melatonin has only a short half life – (meaning the time if stays in the blood) – typically of up to 90 minutes.
Unlike other hormones, the pineal gland does not store melatonin for later release. Rather it is made de novo (fresh) and quickly released into the blood and circulation.
What does melatonin do?
Melatonin has been found to have many functions in the body including:
- regulation of circadian rhythm
- improvement of sleep disorders and jet lag
- regulation of blood pressure
- many anti-cancer effects
- retinal physiology
- regulation of blood sugar
- immune function
- osteoblast differentiation (bones)
- protection against toxicity of chemotherapy
- improvement of wound healing after surgery
- protection against radiation treatment skin damage
- improvement in quality of life
- helps regulate gut motility
- reduction in abdominal cramps
- anti-estrogen effects
- aromatase inhibitor
- anti-aging effects
- protective effect on atherosclerosis
- anticonvulsant activity
- improves migraines and cluster headaches
and more studies are ongoing. Phew! That is a lot of different actions. Melatonin is something we are going to hear more and more about as it is a hot topic in research. In this series of blog posts, we’ll be looking at the evidence of some of the above proposed actions, particularly melatonin’s anti-cancer effects.
How does the body make melatonin?
Melatonin is made in our bodies from the essential amino acid tryptophan (see the diagram at the top of this post). Food sources of tryptophan include meat, poultry, dairy, oats, soybeans, and seeds.
Tryptophan is used to make not only melatonin (via 5-HTP and serotonin) but also a form of Vitamin B3 (nicotinamide). This is important to note because if you are low in vitamin B3/niacin, your body will use its tryptophan sources to make this essential vitamin at the expense of making serotonin and melatonin. Thus if you are low in B3, your sleep and circadian rhythm may be affected.
Additionally, to make serotonin from tryptophan – an essential step in making melatonin – you also need vitamin B6, folate, magnesium, and zinc.
So now we see that anyone with deficiencies in these vitamins/minerals might have a lower production of melatonin and not sleep well. Good reason to make sure you are taking a good multivitamin and mineral.
Light is the most influential factor that modifies our production of melatonin
As we have seen in the graph above, our production of melatonin varies throughout the day and night. We want low levels during the day and high levels overnight.
Production of melatonin is normally inhibited during the day by exposure to blue wavelength light, and then production begins with dim light and darkness.
For centuries, humans relied predominantly on candles and fires for night-time lighting. These sources of light had very little effect on our circadian rhythm because they didn’t emit blue wavelength light. It’s a different story now, however, with our artificial lights (including street lights shining into our bedrooms) and televisions, computer screens, phones, and tablets. They all emit blue light and thus confuse the body’s rhythm into thinking it isn’t night time. This overexposure to light at night can suppress our melatonin production and affect our circadian rhythm and sleep.
During the daytime, sunlight emits blue light, and melatonin production is suppressed – which is what we want. Thus, spending time outdoors during the day often helps you sleep better at night.
If you work indoors under artificial light all day, the blue light emitted isn’t as strong as that from the sun, and so melatonin may only be partially suppressed during the day. Ever wondered why you felt sleepy at work?
Does our diet affect our production of melatonin?
Normal production of melatonin can vary considerably between individuals. In addition to light, dietary factors can also affect our levels:
- First of all, we need enough tryptophan in our diets to produce not only melatonin but also vitamin B3/niacin. If tryptophan is severely restricted, the synthesis of melatonin is significantly reduced.
- As we’ve just learned, vitamin deficiencies (especially B vitamins) and mineral deficiencies can affect our production of melatonin too, as they are involved in the conversion from dietary tryptophan to melatonin.
- Fasting for several days at a time reduces the night time secretion of melatonin.
- Some foods contain melatonin – especially plants. These include tomatoes, olives, barley, rice, some grape varietals, coffee beans, and walnuts . While ingestion of these foods have been seen to increase blood levels, in some people the sleep-inducing aspect of coffee can be negated by the caffeine.
- An interesting nutritional fact is that the concentration of melatonin in mother’s milk shows a clear daily rhythm with increasing levels produced in nighttime milk. This seems to be universal to all mammals. Since milk is the primary component of an infant’s diet, the night-time feed high melatonin content might have significance on the baby’s sleep. But does this mean that while the baby gets the mother’s melatonin through milk and sleeps well, the mother is then left with lower levels and doesn’t sleep as well? Studies haven’t investigated this.
- Alcohol reduces melatonin levels – however if the grapes used in wine have higher levels of melatonin, or beer is made from barley, these might have an additional influence, increasing levels. What have you found?
Does anything else affect our melatonin production?
So finally, in addition to light and food/nutrients, what other factors may affect production of melatonin, reducing levels, include:
- increasing age
- beta blockers
- calcium channel blockers
- changing time zones – flying internationally
- shift work
- poor vision
- blood sugar imbalances
So what can we do to support melatonin?
Considering what affects our production of melatonin, there are some key things that we can change to improve our production of melatonin. The number one influencer is light and dark at day and night. That light/dark cycle involves making sure you have sunlight/natural light during the day time and then darkness at night time.
- During the day, make sure you get some natural sunlight. If you work in an office, try to sit near a window, or go outside for breaks.
- At night time, do you use a computer, smart phone, tablet or television just before going to bed? Use f.lux on your electronic devices which blocks out the blue wavelength light or limit your use of these types of electronics within 2 hours of going to bed.
- At night time, dim your lights in any rooms you are in from around 8 p.m. Are there street lights shining in your bedroom at night? Do you have an illuminated clock by your bedside? Look at how you can block the light in your bedroom. Can you get light-blocking shades? If necessary, maybe you need to wear a dark mask at night.
- Ensure vitamin and mineral sufficiencies and adequate intake of tryptophan-containing foods
- Eat melatonin-containing foods for dinner – and be aware of alcohol and caffeine which might up- or down-regulate melatonin.
- If you take medications that affect melatonin, try taking them earlier in the day if you have the option.
- Reduce/eliminate nicotine.
Future posts in this Melatonin and Cancer series
In subsequent posts, we’ll be covering topics regarding melatonin and:
- sleep and circadian rhythm
- supportive cancer care
- melatonin for radiation treatment
- melatonin with tamoxifen
- breast cancer and melatonin
- the function of the high levels of melatonin produced in the gut
- and more…
If you have any questions about melatonin – leave me a comment and I’ll try and answer it in a subsequent post.
For now, take a look at your evening and sleeping environment and see if you can make some changes that may improve your production of melatonin.