Vitamin D, Sun Exposure and Sleep

High quality sleep is essential for our health and wellbeing. It allows our bodies and minds time to rest and recharge. Overall, sleep plays a role in maintaining physical, mental, and immune system health. Unfortunately, many of us do not get enough of the good quality sleep we need in order to optimize our health and wake up feeling refreshed. Sleep deficiency is correlated to several chronic health problems including high blood pressure, obesity, depression, kidney disease, and heart disease. [1] 

Does vitamin D help with sleep?

Vitamin D frequently makes the list of vitamins that help with sleep- and for good reason! Multiple observational studies, with over 2,000 combined participants, have seen a significant correlation between lower vitamin D levels and shorter sleep duration. [2,3] This is significant given that vitamin D insufficiency is a worldwide concern with up to 70% of the global population having low levels of vitamin D.

While sleep is impacted by a variety of factors, recent research suggests that insufficient vitamin D is correlated to bad sleep including sleeping less and having poorer sleep quality. Associations have also been found between low vitamin D, daytime sleepiness, and increased time it takes to fall asleep at night. 

There are multiple potential mechanisms by which vitamin D may impact sleep. Studies have found vitamin D receptors in parts of the brain that are involved in regulating sleep, including brain areas responsible for the early stages of falling asleep and staying asleep.[4] Vitamin D has also been shown to play a role in the synthesis of melatonin, a hormone that is responsible for helping us fall asleep. [4] 

Does vitamin D improve sleep quality?

A variety of studies have shown that increasing vitamin D levels can improve measures of healthy sleep.  

One study done in chronic pain patients with sleep difficulties found that lower vitamin D levels were correlated with worse sleep difficulties. With daily 1,200 IU vitamin D supplementation these patients saw significant improvement in their time to fall asleep, sleep efficacy, and an average 45 more minutes of sleep per night. [5]

A randomized clinical trial that looked at patients with sleep disorders found that supplementation with vitamin D improved sleep as measured by the Pittsburgh Sleep Quality Index (PSQI). The PSQI is a survey that assesses sleep quality and pattern. This study also found that supplementation with vitamin D reduced the amount of time it took to fall asleep and increased the amount of time that people stayed asleep.[6]

Does vitamin D help with sleep disorders?

Researchers have also suggested a potential link between vitamin D deficiency and sleep disorders such as sleep apnea. Vitamin D deficiency and sleep apnea are both associated with obesity, inflammation, and impaired glucose metabolism. One study that looked at individuals with sleep apnea found that those with sleep apnea had significantly lower vitamin D levels than people without, and that lower vitamin D levels were correlated to more severe sleep apnea.[7] While more research needs to be done on the mechanism of how vitamin D impacts sleep disorders, some researchers have suggested the correlation may be due to the role vitamin D plays in managing inflammation in the body. 

How does sun exposure effect circadian rhythm? 

In addition to creating vitamin D, exposure to light from the sun regulates other processes in the body that impact sleep. Sun exposure plays an important role in regulating circadian rhythm. Circadian rhythm is the body’s internal time clock that regulates our sleep-wake cycle and determines sleep duration. When light enters the eye, it signals to the body that it is time to be awake. When it gets dark at night, melatonin levels in the body increase which causes us to become drowsy. Since melatonin levels are controlled by light exposure, exposure to the sun plays an important role in regulating sleep time.

Exposure to light, even artificial light, before trying to sleep can disrupt the sleep-wake cycle and can lead to less and poorer sleep. To optimize sleep quality, it is best to make sure the sleep cycle is regulated by getting light in the morning when you wake up and avoiding light as much as possible at nighttime before bed. [8]

How much vitamin D should you take for sleep?

Vitamin D is not a ‘one size fits all’ approach, and while there is no single amount of vitamin D that works for everyone, experts agree that maintaining sufficient levels of vitamin D is important for widespread health. A sufficient vitamin D level is usually considered above 30 ng/mL.  

Among the medical community, there is debate on the best way to get vitamin D. Some doctors recommend oral supplements, but there are a variety of reasons why ingested vitamin D may not be the best option. Oral vitamin D supplements are not effective for a surprisingly large number of people, and don’t provide the same health benefits as exposure to light. To learn more about this topic, click here to read our article about why vitamin D pills fall short. 

Obtaining vitamin D from light allows your body to self-regulate vitamin D production and make as much as your body needs to stay healthy, without any risk of overdose or toxicity. Unlike with oral supplements, you cannot overdose on vitamin D produced by your skin. If you have enough vitamin D, your body will simply produce less.