Sleep is one of the pillars of health, without which none of the human body can’t function properly. If a person has trouble sleeping, their body is unable to carry out the necessary regenerative processes, which can lead to a series of physical and mental issues over time. There is a clear link between sleep deprivation, disrupted circadian rhythms and the risk of various chronic diseases.

Sleep disorders affect a huge amount of people as a result of modern lifestyles, reaching ~30-50% of the population according to some surveys(1) and more than half of people working multiple shifts(2).

Sleep disorders can mean several things, including: 

• Lack of adequate and sufficient sleep
• Difficulty falling asleep or waking up
• Frequently waking up at night (fragmented sleep)
• Sleep apnea

Therefore, there’s a great need for effective and evidence-based natural therapies that improve the quality of our sleep, preferably without side effects. Interestingly, one of these natural agents is vitamin D, which has been clearly shown in several recent meta-analyses to help sleep, among its many other benefits.

The role of vitamin D in sleep

Although we do not yet know all the exact reasons why vitamin D is important for sleep, it’s probably related to the fact that vitamin D receptors are also found in areas of the brain involved in sleep regulation.(3) Vitamin D's anti-inflammatory and immune-supporting effects may also play a role in better sleep.

Serotonin and dopamine, also known as the happiness hormones, are both necessary for restful sleep, and vitamin D is key to their function.(3)  Serotonin is also important because it’s a precursor of melatonin, which is also essential for quality sleep and overall health.

The circadian rhythm is strongly linked to vitamin D as well, as it’s naturally produced when one’s exposed to sunlight during the day. It’s possible that the beneficial effects of vitamin D are partly due to the tuning of our circadian rhythm.

Vitamin D deficiency can lead to sleep disorders

A review study published in 2022 reported on the link between vitamin D deficiency and sleep disorders.(3) Its main findings were:

• Children with vitamin D deficiency had reduced sleep duration and poorer sleep quality. Vitamin D deficiency was also associated with later bedtimes, suggesting a negative effect on circadian rhythms.
• Low vitamin D levels, physical inactivity and high BMI all increased daytime fatigue, but low vitamin D levels had the strongest effect.
• Children and parents who snored had a much higher percentage of vitamin D deficiency.

It’s clear that low levels of vitamin D can impair the quality of sleep in a number of ways, but the question is whether supplementing it can improve these complaints.

The impact of vitamin D supplementation on sleep

A new meta-analysis published in December 2022 specifically examined the effectiveness of vitamin D intake on sleep quality.(4) A total of 5 studies were selected, where participants received 1000 IU, 2000 IU or 50,000 IU of vitamin D3 every day or every two weeks. Sleep quality was assessed using a survey.

In all cases, supplementation with vitamin D improved the sleep quality of the participants, but the biggest change was observed with 50000 IU, which corresponds to ~3500 IU of vitamin D3 per day.

Lower doses also improved sleep quality, but to a lesser extent: it’s likely that too little vitamin D3 wasn’t enough to achieve significant results. It must be noted that vitamin D consumption didn’t cause any side effects in these or other studies.

Another meta-analysis, also published in 2022, summarised the results of 31 randomised trials analysing the effectiveness of different dietary supplements on sleep.(5) Only certain amino acids, melatonin and vitamin D3, achieved significant improvements in sleep quality.

Summary

Supplementation of vitamin D3 and the regulation of vitamin D levels is not only essential for its effects on our immune system, but is also necessary for numerous other biological processes. A large body of research shows that vitamin D deficiency impairs sleep quality, while adequate supplementation significantly improves it.