Melatonin is one of the hormones that control circadian rhythms. A lot of people take melatonin to treat insomnia, but it does a lot more than control sleepiness - it’s also important for weight, insulin sensitivity and metabolic health, aging, and gut health. Here’s a look.
Melatonin and Sleep
Melatonin is a hormone that your body naturally makes on its own. It’s part of a normal circadian rhythm - it’s naturally low in the morning and rises in the evening as you get sleepier. In the 1970s and 80s, researchers discovered that supplemental melatonin induced sleepiness, and since then it’s been used as a sleeping aid. It’s not habit-forming, and generally considered very safe, even if doesn’t actually work well for everyone.
Melatonin lowers body temperature and generally helps align the body’s internal clock to the fact that it’s night now. In general, studies support the claim that it works for falling asleep faster, although the size of the benefit varies quite a lot and for some people it might not be noticeable in the real world. People with particular circadian disorders may see more benefit than the general population.
Melatonin may be particularly important for sleep in children with autism-spectrum disorders. This review goes over some of the evidence: children with ASD have lower melatonin levels in general, possibly for genetic reasons. The authors went over several studies and ultimately concluded that melatonin (at a typical adult dose of 3-6mg, taken at bedtime) may be particularly helpful for helping children get to sleep and stay asleep for longer. Overall, the studies found that children fell asleep an hour earlier with melatonin, which is nothing to sneeze at.
Melatonin is also useful for people who have trouble with maintaining a normal sleeping pattern; for example, people who travel between time zones a lot, or people who work an unusual schedule where they work at night and sleep during the day. A Cochrane review found that melatonin was “remarkably effective” for treating jet lag, if taken close to the target bedtime. For shift workers, another review found that it improved length of sleep but not necessarily quality.
How Much and When?
The typical dose of melatonin used in studies is 3mg, taken at night. This study suggested that even lower doses from less than 1mg to 2mg might be better, particularly in older adults.
There are also ways to support melatonin production without supplementing. For example, you could…
- Avoid light at night. Light, especially blue light, suppresses the production of melatonin. If you avoid it before bed, or only use dim light, your body will produce melatonin more easily.
- Sleep! Sleep deprivation reduces melatonin levels, so it sets off a vicious cycle where you can’t sleep because your melatonin is low because you haven’t been sleeping.
- Foods that provide melatonin. Melatonin is found in a variety of plant foods, but the amount varies depending on how the plant was grown (so there’s no real way to say that Food X contains Y amount of melatonin, because it depends on whether the particular plant you’re eating grew under stressful conditions, how much light it got, and a bunch of other factors). But it does seem that grapes and red wine may be particularly rich in melatonin, and this study found that subjects who drank juice from oranges, pineapples, and bananas had higher melatonin concentrations in their blood afterwards.
Melatonin and Other Areas of Health
Melatonin doesn’t just work for sleep. It also affects all kinds of other things that are relevant to circadian rhythms and the stress response.
For one thing, It’s being investigated as a treatment for Irritable Bowel Syndrome. A lot of the melatonin in your body is actually produced in the lining of the gut - melatonin levels in the gut are between 10 and 100 times more concentrated than they are in the blood. Melatonin helps regulate motility and inflammation in the gut. Studies have shown that melatonin supplements can improve the symptoms of IBS in various different ways, especially abdominal pain and overall quality of life.
Melatonin may also affect weight. Melatonin directly affects levels of leptin and adiponectin, two very important hormones for weight regulation. In fact, that may one be one reason why sleep deprivation is so strongly connected to obesity: sleep deprivation reduces levels of melatonin, which then sends leptin all out of whack. Melatonin also directly helps regulate insulin sensitivity and the activity of brown fat. This study directly showed that melatonin helped reduce inflammation and improve insulin sensitivity in rats with diet-induced obesity. In this study, 5mg of melatonin per day combined with dietary changes helped postmenopausal women lose weight (that’s significant because postmenopausal women tend to be the people who find weight loss the hardest).
But it doesn’t stop at weight and gut health. Melatonin can also affect aging, because it’s a powerful antioxidant that affects inflammatory processes and even epigenetic changes that can make a person’s life longer or shorter. This review goes over all the ways that melatonin status can modulate the aging process, especially brain aging.
Melatonin also affects sex hormones and reproductive health, in men and in women, in ways that might be significant for hormone-related diseases. A gene associated with variations in melatonin receptors is also associated with hormonal changes in PCOS (Polycystic Ovary Syndrome, a disease where women have unusually high levels of male hormones), and women with PCOS have alterations in melatonin levels compared to healthy controls.
Related to its effects on reproductive hormones, melatonin has also shown some promise as a therapy for breast cancer. People with disruptions in melatonin signaling, like shift workers, have higher rates of breast cancer, and there’s some evidence that melatonin itself acts on cancer cells in various ways. This study goes through a lot of the evidence to date - nobody’s claiming that melatonin “cures cancer,” but it might be one aspect of prevention or treatment.
Of course, all these other things are related. Degenerative brain diseases in aging are related to weight and metabolic health, weight is linked to sex hormones, and gut health is also strongly tied to weight and to aging.
Summing it Up
Melatonin is important for sleep, but sleep isn’t the only thing it does, and insomnia isn’t the only time it can be useful. Melatonin also affects weight, insulin sensitivity, aging, hormonal balance, and gut health, particularly Irritable Bowel Syndrome. Supplemental melatonin has shown some benefit for all of those conditions.