The Melatonin-Sleep Connection

By Michael Stanclift, ND 

Without sleep, many aspects of our health suffer. We may see startling impacts in our brains and our ability to learn, our cardiovascular systems, and our immune health. Prominent UC Berkeley sleep researcher Dr. Matt Walker reminds us that a lack of sleep can age our bodies up to a decade faster.1 His experiments revealed a single “all-nighter” episode of sleep deprivation chops our learning by 40%—gradewise, that’s the difference between an A and an F.2 He points out that hospitals see a 24% surge in cardiovascular cases just after the spring change to Daylight Saving Time (when we lose an hour of sleep) and a corresponding 21% dip in the fall when we get that hour of sleep back.3 A single night of shortened sleep (4 hours) may reduce the activity of our immune system’s natural killer cells by 70%.4

Why do we see such striking effects from sleep? Much of those effects can be tied to our daily (circadian) rhythms and the role of melatonin.

Melatonin is a hormone, made in our brain’s pineal gland. Our bodies make melatonin from an amino acid, tryptophan, found in our diet.5,6 With the help of B vitamins (folate and B6), our bodies turn tryptophan into serotonin, a neurotransmitter associated with moods, and serotonin can then be further processed into melatonin.5 Light exposure to our eyes blocks our brain’s signal to make melatonin, which is why melatonin and light are the most influential time signals to our natural circadian clocks.6 It’s no surprise then that not enough light during the day or too much light exposure (think electronics and room lighting) later in the day can disrupt our sleep/wake cycle.7 Blue light is strongest at suppressing our own melatonin production, and unfortunately some of our favorite devices (televisions, computer screens, phones) produce quite a bit of blue light. Researchers showed blocking blue light by wearing amber-colored lenses two hours before bedtime for one week may prevent melatonin suppression and improve sleep in people who complained of sleep problems.7

But melatonin isn’t just important for sleep. For example, it positively influences both our fast (innate) and slower (adaptive) immune responses.8 Melatonin affects nearly every cell in our immune system, and the age-related decline in our sleep and immune responses are likely connected.8 When we think about our immunity, we should also think about how much sleep we’re getting and the associated melatonin.

For some people, supplementing melatonin for better sleep might make sense. Melatonin is safe when used short-term. 6 It’s effective for helping people get to sleep, and the effect appears to be stronger by scientific physiological measures than by our subjective self-reports, which means you may not appreciate how much it helps.6 Melatonin doesn’t appear to change the quality of sleep we get, our perception of a sleep problem, or nighttime waking.6 One scientific review suggests melatonin should be combined with cognitive behavioral therapy for insomnia (CBT-I) for best results.6

As Dr. Walker says, “Sleep, unfortunately, is not an optional lifestyle luxury. Sleep is a nonnegotiable biological necessity.”1 To find out more about the benefits of sleep, click here.


  1. Walker M. TED. Published 2019. Accessed March 2, 2021.
  2. Yoo SS et al. Nat Neurosci. 2007;10(3):385-392.
  3. Sandhu A et al. Open Heart. 2014;1(1):e000019.
  4. Irwin M et al. Psychosom Med. 1994;56(6):493-498.
  5. Peuhkuri K et al. Food Nutr Res. 2012;56:10.3402/fnr.v56i0.17252.
  6. Baglioni C et al. J Clin Med. 2020;9(6):1949.
  7. Shechter A et al. J Psychiatr Res. 2018;96:196-202.
  8. Srinivasan V et al. Immun Ageing. 2005;2:17.
Michael Stanclift, ND
Michael Stanclift, ND is a naturopathic doctor and senior medical writer at Metagenics. He graduated from Bastyr University’s school of naturopathic medicine and practiced in Edinburgh, Scotland, and Southern California. He enjoys educating other healthcare providers and impacting the lives of their many patients. When he’s not working, he spends his hours with his wife and two children.

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