Science Update

Recent Review Explores Relationship Between Vitamin D Supplementation and Sleep Quality

The prevalence of vitamin D deficiency in the US is approximately 24%. Severe vitamin D deficiency may occur in roughly 6% of the US population. Although these numbers are believed to vary based on factors that include age, race, and latitude, adequate vitamin D levels are an essential nutrient for the human body.

Vitamin D has been linked to certain aspects of sleep quality, including an increased risk of sleep disorders, according to recent research. The mechanism of action that associates vitamin D with sleep quality is not yet fully understood, but some theories include the role of vitamin D in modulating certain inflammatory markers involved in sleep regulation, such as tumor necrosis factor-alpha. Others postulate that the presence of vitamin D receptors in specific parts of the brain may affect sleep.

Deficiencies in vitamin D have been associated with nocturnal awakenings and shorter sleep duration in both pediatric and adult clinical studies. A meta-analysis of observational studies included data from more than 9,000 individuals that reported increased odds of shorter sleep duration and sleepiness in the presence of vitamin D deficiency.

A recently published systematic review explored the potential efficacy of supplementation with vitamin D on sleep quality and the incidence of sleep-related disorders. More than 19,000 studies were screened for inclusion in this review, with 19 of the studies meeting the inclusion criteria. The average doses of vitamin D supplementation were between 1,000 IU and 7,000 IU. Most studies used the form of vitamin D cholecalciferol, or D3, for supplementation.

Several studies that were included in this systematic review assessed the efficacy of supplementation with vitamin D on sleep quality parameters by using the Pittsburgh Sleep Quality Index (PSQI). Statistically significant improvements in PSQI scores were reported by meta-analysis.

Perhaps, due to the study designs and small sample sizes, some results of the systematic review were conflicting. For instance, one study that assessed the effects of vitamin D supplementation for 6 months for restless leg syndrome (RLS) reported decreases in the severity of RLS. However, another study of vitamin D supplementation reported no difference in the severity of RLS as compared to a placebo.

Vitamin D is well-known for its multiple roles in the support of musculoskeletal health, a healthy immune response, and cellular health. Additional clinical research studies with larger sample sizes are necessary for further conclusions to be drawn, yet indications are that adequate vitamin D levels may also support a healthy sleep cycle. Vitamin D can be obtained from sun exposure, supplementation, and certain foods, including beef liver, egg yolks, fortified dairy and non-dairy products, and the flesh of fatty fish.

By Colleen Ambrose, ND, MAT