As a sleep scientist, this is a question that has me squirming a little.. my typical response varies between: “ it depends” and “perhaps”! I know that’s not terribly helpful. I’d love to give a clearer answer, but in some cases we just don’t have the evidence to prove whether a specific supplement has an impact, or we might have promising evidence that a supplement could address a deficiency, but not that it will change anything in a healthy population.
In this article I will start by explaining why it’s often difficult to make recommendations about sleep supplements on the basis of existing evidence. There are several questions that I would encourage you to have in your mind when you consider buying a supplements.
- Is it better than a placebo?
- Does it help people like me?
- If it improves sleep, is the impact meaningful?
- Is it safe for me?
I’ll explain why these questions are important. I’ll then give a quick summary of the latest research into a range of popular supplements, as of August 2023:
- Vitamin D
New research is emerging all the time, so we will try and update this article regularly.
Is it better than placebo? Is there evidence from randomised placebo-controlled trials?
One of the most common reasons for poor sleep is worry about not sleeping. Imagine that I give you a pill, with no active ingredients, and tell you: “This will help you sleep”. The relief of knowing that you have a solution might help you to relax. If you’re tired - as most poor sleepers are - you’ll fall asleep more easily. If you’re less stressed, you might also get into a deeper sleep, and wake up feeling more energised.
In fact, studies have found that taking a placebo - a completely inactive substance - typically helps people fall asleep 20% faster, and stay asleep 20% longer. It’s been estimated that more than 60% of the effectiveness of sleeping pills is due to the placebo effect (Winkler 2015).
For confidence that something really improves sleep, we ideally want to see evidence from multiple tests where a supplement is compared to a placebo, or another active treatment.
The gold standard research design is called a placebo-randomised controlled trial, where participants are allocated at random to receive either the intervention, or a placebo. For a high degree of confidence,
The problem with most sleep supplements is that they haven’t been tested against placebo, or if they have, the trials are very small.
Does it help people like me?
The gold standard treatment for insomnia is a talking therapy called Cognitive Behavioural Therapy for Insomnia (CBT-I). CBT-I has been tested hundreds of times, in thousands of people, and has reliably been shown to improve both sleep quality and daytime energy and mood.
Researchers have combined the results of many trials together into something called a ‘meta-analysis’, which gives greater rigour to the conclusions. Using this strategy, CBT-I has been demonstrated to be effective in men and women of different age groups, during pregnancy, menopause, in people with other chronic conditions and mental health disorders. This means that we can be confident in recommending CBT-I to most people.
One of the problems with supplements is that trials are typically small, involving anything from 10 to 100 people. This means the results may not generalise to other groups. Supplement trials often do not test whether participants have a deficiency in a substance before the trial starts, or whether the supplement corrects this, so it’s hard to know for whom the supplement is most likely to be effective for.
If it improves sleep, is the impact meaningful? Would something else be more effective?
Sleep supplement trials often seem to find an impact on one aspect of sleep, such as time to fall asleep, but perhaps not on other measures like overall sleep time or quality. You may need to read all the detail in the results before deciding whether the impact would be meaningful to you. It may be that CBT-I or regular exercise would have more reliable impact across all sleep outcomes. For example, CBT-I has been found to have lasting effects several years after the original intervention. Most supplement research only lasts for weeks or months, so the longer term impacts are unknown.
Is it safe for me?
With any sleep intervention, it’s crucial to look at any side effects or safety risks, especially if you are taking other medication. Most over-the-counter remedies have been deemed low risk, but always read the small print, and ask your doctor if you are unsure about taking any sleep supplement.
OK, so what does the evidence say about some of the most popular sleep supplements?
- Vitamin D
Magnesium Supplements and Sleep
Magnesium is found naturally in the diet in leafy green vegetables, legumes, nuts and seeds, yogurts, and wholegrains. Several large population studies have found that poor sleepers are more likely to be deficient in magnesium. Magnesium is widely used to regulate many processes throughout the body. Its role in sleep is not well understood, but it may help to stabilise mood and reduce anxiety and depression.
However, just because magnesium deficiency is common with poor sleep, it does not necessarily follow that supplementing magnesium will solve sleep problems. A meta-analysis published in 2021 identified 3 studies which compared magnesium supplements to placebo, given 2-3 times a day, in 151 adults aged 55+ (Mah & Pitr 2021). They found that magnesium helped people fall asleep 17 minutes faster, and stay asleep 16 minutes longer - but the effect on sleep time was not statistically significant.
A more recent analysis looking randomized clinical trials showed “an uncertain association between magnesium supplementation and sleep disorders” - in other words, no consistent benefits for patients with insomnia (Arab et al 2023). The authors commented that well-designed randomized clinical trials with a larger sample size and longer follow-up time (more than 12 weeks) are needed to further clarify the relationship.
Ashwaganda and Sleep
Withania somnifera , commonly known as Ashwagandha, has been used for centuries for various purposes in Ayurveda, traditional Indian medicine. It is an evergreen, branching shrub that originates in Western India and Mediterranean regions. Extracts from the roots and leaves have been used for multiple purposes, such as to relieve rheumatic pain, joint inflammation, cognitive disorders, anxiety and stress disorders, male infertility, and to improve physical performance.
A recent meta-analysis of 5 randomised controlled trials in 400 subjects found a small but significant improvement in sleep quality in comparison to placebo (Cheah et al 2021). All trials were conducted in India. The effects on sleep were more marked in adults diagnosed with insomnia, with a treatment dosage ≥600 mg/day, and treatment lasting ≥8 weeks. Ashwagandha extract was also found to improve mental alertness on rising and anxiety level, but had no significant effect on quality of life. No serious side effects were reported. The mechanism through which Ashwaganda impacts sleep is not entirely clear, but animal studies and in vitro research suggests that it can have neuroprotective, anti-inflammatory and chondroprotective effects (impacting on joint health), e.g. (Bashir et al 2023).
Vitamin D Supplementation and Sleep
Vitamin D is essential to bone formation. It is mainly produced by the skin after sun exposure, and it can also be obtained from food and supplementation. Around 1 in 6 adults in the UK are deficient in vitamin D, with higher rates in the winter and spring. Low vitamin D has been linked to a wide range of health risks including risks of infection, depression and cardiovascular disease, as well as shorter sleep and more fragmented sleep. Since sunlight is required for both Vitamin D production AND is a key regulator of our circadian rhythms, it might be that a lack of sunlight is driving both poor sleep and vitamin D deficiency. A recent meta-analysis examining the effect of supplementing with vitamin D for sleep suggested that the results were “promising” for sleep quality, but that the impact on sleep duration, and sleep disorders need further investigation (Abboud 2023).
L-Tryptophan and Sleep
Amino acids are the building blocks of proteins and certain brain-signalling chemicals.
L-tryptophan is an essential amino acid which has to be consumed in the diet. The body converts it into serotonin, which can influence both mood and sleep. L-tryptophan is found in turkey and chicken as well as bananas, eggs, milk, fish, soy, tofu, pumpkin and sesame seeds. Most people consuming a healthy diet are unlikely to be deficient in L-tryptophan.
A recent meta-analysis combined the results of 4 studies looking at tryptophan supplementation (Sutanto et al 2022). The authors found that taking a tryptophan supplement reduced the amount of time awake during the night, but did not significantly affect any other metrics of sleep including duration or time to fall asleep. People taking doses >=1g stayed awake for an average of 29 minutes during the night; which was 25 minutes less than those taking doses of <1g.
Valerian and Sleep
There are claims that the roots of the Valeriana officinalis — a tall, flowering grassland plant — can reduce the time it takes to fall asleep and improve sleep quality. Valerian root extract is sold as a supplement in capsule or liquid form, or as a tea. It may increase the availability of GABA in the brain, which has a relaxing effect. Although a few studies indicate some benefit for sleep quality, other studies haven't found any benefits. It may not be more effective than placebo. Some of the inconsistencies could be due to different variants and preparations of valerian. Valerian is generally viewed as relatively safe, with few side effects, but may occasionally cause headaches, stomach pain or dizziness. It may interact with other medications, so if you’re taking other medications or have a health condition, check with your doctor before trying it. The European Sleep Research Society concluded that Valerian is not recommended for the treatment of insomnia because of poor evidence that it is helpful (Riemann et al 2017).
Chamomile and Sleep
Extract of dried chamomile flowers is a traditional herbal remedy for poor sleep. Chamomile is argued to have sedative effects via the flavonoid apigenin, which is thought to bind to the GABA-A receptors, like benzodiazepine drugs, to cause a relaxing effect. A recent meta-analysis found some evidence of an improvement in perceived sleep quality, but no evidence that chamomile reduced insomnia severity compared with placebo (Hiue et al 2019). Chamomile can have blood pressure lowering and blood thinning effects, so ask your doctor if you are on other medication.
As you can see from dates on the articles referred to above, the question about whether supplements for sleep are effective is a very active area for research. Always look for evidence from published controlled trials before spending money on supplements. If you’re not sure about a particular product, it’s always worth contacting the company and asking to see the evidence of their effectiveness. If the research doesn't exist, look for products with a money back guarantee.
In the latest clinical guidelines for insomnia from sleep experts in Britain, Europe and America, Cognitive Behavioural Therapy for Insomnia is recommended as the first line treatment approach for adults of any age, so this is a good place to start.