What the science says about melatonin, magnesium and other sleep supplements

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Do you struggle to fall asleep at night, or find yourself routinely waking up at 3 a.m.?

Many people experience bouts of insomnia at some point in their lives, often due to anxiety. When these sleep issues persist for several months or longer, it’s usually a good idea to visit a doctor to see if you have an underlying condition, like depression, restless legs syndrome or sleep apnea, that requires medical treatment.

But for occasional periods of insomnia that leave you feeling bleary-eyed, experts say there may be some dietary supplements and even foods that can help.

It’s important to recognize that no dietary supplement is going to radically improve your sleep. Supplements shouldn’t be viewed as a long-term solution. And almost all supplements carry the risk of side effects.

But some may produce modest benefits, such as helping you fall asleep slightly faster at night, and carry minimal side effects when taken in smaller doses.

We spoke to sleep and nutrition experts and reviewed dozens of studies to find out what the science says about five popular supplements. Here’s what you need to know.

Melatonin

Melatonin is one of the most popular sleep supplements, and for good reason.

A hormone that’s secreted in the pineal gland of your brain, melatonin regulates your sleep-wake cycle by synchronizing your body’s internal clock with the outside world. It’s produced primarily in the evening. But melatonin isn’t going to quickly send you off to sleep like a fast-acting sleeping pill. Instead, it promotes sleepiness by signalling to your body that it’s nighttime.

For that reason, melatonin supplements are most helpful for people with sleep timing problems, said Phyllis C. Zee, the medical director of the Center for Circadian and Sleep Medicine at the Northwestern University Feinberg School of Medicine. That includes people with jet lag, shift workers who work late at night or early in the morning, and people who routinely struggle to fall asleep until it’s extremely late at night.

For those people, taking a melatonin supplement in the evening can set their biological clocks earlier, helping them fall asleep and wake up earlier, Zee said.

Melatonin supplements may also benefit older adults, because melatonin levels naturally decline with age, as well as postmenopausal women, said Fariha Abbasi-Feinberg, a sleep medicine specialist and spokeswoman for the American Academy of Sleep Medicine. “I think some people are more sensitive to it and can get some improvements in their sleep from it,” she added.

Many studies have examined whether melatonin can alleviate insomnia, and the data is mostly mixed, Abbasi-Feinberg said. Some studies have found that it can help people fall asleep faster and sleep more soundly.

But the American Academy of Sleep Medicine says that there “isn’t enough strong evidence on the effectiveness or safety of melatonin supplementation for chronic insomnia” to recommend its use. If you find that you’re having trouble falling asleep or staying asleep at least three times a week for three months or longer – the criteria for chronic insomnia – then you should visit a doctor or a sleep specialist, Zee said.

If you are going to try melatonin for an occasional sleep timing problem, it’s best that you use a low dose, around half a milligram to three milligrams, said Zee at Northwestern. You also have to get the timing right: Melatonin should be taken about two hours before bedtime for it to be most effective.

Some studies have shown that several melatonin products are “inaccurately labelled,” with several containing more melatonin than advertised. When shopping for melatonin, check for third-party certifications, which mean the products were independently vetted for purity and potency. Look for the black and yellow “USP Verified” logo or the blue and white “NSF” logo. You can also go to each group’s website to look up products.

(The FDA doesn’t approve or regulate supplements the way it does prescription drugs.)

Magnesium

Magnesium plays an important role in good sleep. It promotes relaxation, calms the nervous system and helps produce melatonin.

Studies have linked inadequate magnesium consumption to shorter and poorer quality sleep. Scientists have also found in animal studies that magnesium deficiencies lead to reductions in melatonin levels.

Magnesium supplements are widely touted as a sleep aid, and some studies have found that it can be helpful for people experiencing insomnia. But the studies showing benefits have been mostly small and not very conclusive.

In one systematic review and meta-analysis published in 2021, scientists looked at three clinical trials involving 151 older adults with insomnia that compared magnesium supplements to a placebo. It found that people assigned to take magnesium fell asleep about 18 minutes faster at night.

The researchers cautioned that more rigorous studies were needed. But given that magnesium is “very cheap and widely available,” they added, they could find no evidence discouraging its use for insomnia in older adults.

While most people get plenty of magnesium from their diets, Abbasi-Feinberg said, she does occasionally recommend a low dose to people who routinely struggle to fall asleep.

“I’ll tell them to start with 100 or 200 milligrams of magnesium and see if that makes a difference,” she said.

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She stressed that people should stick to a low dose because magnesium can have side effects, including nausea, vomiting and diarrhea. These side effects typically occur with doses above 350 milligrams. “It’s important to note that more is not better,” said Zee at Northwestern. “Check with your doctor and let them know that you’re taking magnesium and the dose to avoid possible interactions with other medications or medical conditions.”

Probiotics

A healthy gut may promote healthy sleep. Studies have found that higher levels of gut microbiome diversity – generally considered a sign of a healthy gut – are associated with longer, better sleep and fewer nighttime awakenings.

Many hormones and metabolites that are produced by our gut microbes act directly on the brain to influence sleep regulation, including neurotransmitters like serotonin, said Chris Damman, a gastroenterologist at the Digestive Health Center at the University of Washington Medical Center and the author of Gut Bites MD, a blog on gut health and nutrition.

That’s one reason Abbasi-Feinberg encourages her patients to consume probiotics, which are live bacteria and other microorganisms that confer health benefits. But probiotic supplements – which are available in capsules, gummies, powders and pills – can have some downsides. For one, they tend to contain concentrated doses of just a few strains of bacteria. Studies have shown that taking them may actually reduce the microbial diversity in your gut.

Instead, Abbasi-Feinberg recommends that you get probiotics from fermented foods, like plain yogurt, kefir, kimchi, sauerkraut and tempeh. These fermented foods typically contain not only probiotics (the live microbes) but also prebiotics (the fibre the microbes eat) and postbiotics (the vitamins and nutrients they produce).

One clinical trial involving 29 people found that older adults who drank a little more than a half cup of fermented milk every day for three weeks fell asleep more quickly at night and had fewer nighttime awakenings compared to when they drank a placebo. Several studies have shown that fermented foods also have other health benefits, including reducing inflammation.

Abbasi-Feinberg said she tells patients to add fermented foods to their diets because they have the potential to improve their sleep and have very little downside. “If there’s no risk involved and the benefit is there, then they’re worth a try,” she added.

Vitamin D

It’s well known that vitamin D is essential for building strong bones. But it’s also necessary for good sleep. Vitamin D helps the body convert tryptophan into serotonin, a neurotransmitter that plays an important role in how well and how long you sleep. As one recent study noted, vitamin D receptors have been found in regions of the brain that regulate sleep, suggesting that it plays a direct role in our nightly shut-eye.

“Vitamin D deficiencies can cause issues with low energy and low mood,” said Abbasi-Feinberg, “and sleep can be affected as well.”

There’s some evidence that taking vitamin D can improve sleep. But the data are mixed, and not every study has shown benefits. Also, some of the studies involved taking a single large dose as a shot at weekly or biweekly intervals, rather than a daily pill.

Abbasi-Feinberg said she sometimes encounters patients with sleep problems who work from home and rarely get any exposure to morning sunshine. “They roll out of bed and turn their computer on and, boom, they’re at work and they don’t get outside,” she said.

That can be a problem because exposure to sunshine helps your body produce vitamin D. It also halts production of melatonin and resets your circadian rhythm, which can help you sleep better at night. For that reason, Abbasi-Feinberg often prescribes morning sunshine to her patients – rather than a vitamin D supplement.

“The best way to get vitamin D is to go out into the sunshine,” she added.

Ashwagandha

This popular evergreen shrub has been used for centuries in Ayurveda – a traditional medicine system originating in India – for a variety of reasons. Nowadays, it’s commonly recommended as a sleep aid. There’s some evidence that it can help with insomnia. But the data are not conclusive.

Advocates of ashwagandha say it’s useful for insomnia because it alleviates stress and anxiety. In a meta-analysis published in 2021, scientists analyzed five randomized trials involving 400 people that looked at the effects of ashwagandha on sleep compared to a placebo. They found a “small but significant effect” of ashwagandha on overall sleep. People who were assigned to take an ashwagandha supplement daily slept on average about 25 minutes longer each night and had greater improvements in sleep quality compared to people who were given placebo.

But the scientists also cautioned that there was limited data on ashwagandha’s potentially serious side effects, and they said that more research was needed to determine whether it was safe for long-term use. (It has been linked to a handful of cases of liver toxicity.)

Abassi-Feinberg said she doesn’t necessarily discourage people from trying ashwagandha or other Ayurvedic remedies to help them sleep if they’re not known to be harmful. But she feels that there’s not enough strong evidence to recommend them. “I’m not enthusiastic about them because I feel like the data just aren’t there yet,” she added.

Experts also recommend that some people avoid ashwagandha altogether for safety reasons, such as women who are pregnant or nursing, people with an autoimmune, liver, or thyroid disorder, and people who are taking sedative medications such as gabapentin or benzodiazepines.

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