March 2020
Catherine Ward

Did you know that vitamin D, also known as the “sunshine vitamin,” plays a big role in your night, too? If your vitamin D levels are on the lower end, it could actually be affecting your sleep. Worry not, though! Below, we’ll go over the evidence behind the effect vitamin D has on sleep and give you some suggestions for your best night of rest yet.

The science of vitamin D and sleep

Several studies have shown an association between vitamin D levels and different measures of sleep. Low blood levels of vitamin D are associated with decreased sleep time, decreased sleep efficiency, and increased daytime sleepiness. To understand these terms, let's go over some definitions:

  • Sleep time is simply the amount of time that you sleep
  • Sleep efficiency is a measure of sleep based on the time it takes you to fall asleep and how many times you wake throughout the night
  • Daytime sleepiness is a subjective measure of how sleepy/tired a person felt throughout the day

In short, these studies concluded that if your vitamin D is low you might sleep less, and even when you do sleep, it may be less efficient, less restful sleep. Translation? You’ll be sleepy the next day.

Furthermore, another study showed that improving vitamin D levels by taking a supplement improved sleep. This is important because it's one thing to say that low vitamin D is associated with undesirable sleep measures, but another to show that increasing vitamin D actually improves sleep. A randomized, controlled trial is needed to show a direct relationship between vitamin D and sleep. In this randomized, controlled trial study by Huang et al., patients were given supplements based on their vitamin D status. Overall, their vitamin D status improved from a mean of 18.57 ng/mL up to 26 ng/mL post-intervention, and their sleep time increased by about 45 minutes.

Several studies even saw a dose-dependent relationship between vitamin D levels and sleep. This adds to the evidence that there is a direct, linear relationship between vitamin D and sleep measures. This also means that improving your vitamin D by any amount will improve your sleep. While reaching your optimal zone will result in the best sleep, just improving your vitamin D even just a little bit could improve your sleep by the same amount.