Science Spotlight

Sunshine vitamin getting in the way of a good night’s sleep

McTiernan Studies (Public Health Sciences)

Vitamin D, the current “It” vitamin, may reduce the risk of a wide range of diseases including multiple sclerosis, autoimmune disorders, and certain cancers. Furthermore, low levels of this vitamin are associated with health outcomes such as insomnia and depression.

Vitamin D is a group of fat-soluble vitamins responsible for intestinal absorption of calcium and phosphate. Two major forms of vitamin D exist.  Vitamin D2 (ergocalciferol), found in plants and produced by ultraviolet B irradiation of ergosterol, is found in fortified foods and supplements. Alternatively, Vitamin D3 (cholecalciferol), a product of ultraviolet B irradiation of 7-dehydrocholesterol, is synthesized in the human epidermis or consumed in the form of natural or fortified food sources or as a supplement.

Several trials have reported the effects of vitamin D supplementation on depressive symptoms, however few studies have examined the associations between vitamin D, sleep, and health-related quality of life (HRQOL). To assess this, Drs. Caitlin Mason, Anne McTiernan, and colleagues (Public Health Sciences Division) examined the effects of oral vitamin D3 supplementation on changes in HRQOL subscales (physical functioning, role-physical, bodily pain, vitality, general health, social functioning, role-emotional, and mental health), depressive symptoms, and sleep quality, among overweight or obese postmenopausal women with insufficient levels of circulating vitamin D participating in a structured behavioral weight loss program. The results from their study are published in a recent issue of Preventive Medicine.

The investigators recruited overweight and obese postmenopausal women with low levels (10-32 ng/ml) of serum 25-hydroxyvitamin D [25(OH)D] and randomly assigned them to 12 months of weight loss along with 2000 IU oral vitamin D3/day or weight loss and daily placebo. The weight-loss program included a reduced-calorie diet and 225 min/week of moderate-to-vigorous aerobic activity. They assessed eight subscales of HRQOL, depressive symptoms, and sleep quality at baseline (pre-randomization) and for 12 months. In an intent-to-treat analysis, where individuals are analyzed according to their initial randomized treatment and not the actual treatment received, the investigators compared mean 12-month changes in these measures between the two trial arms using generalized estimating equations.

The investigators found, compared to placebo, women receiving vitamin D did not experience any significant change in HRQOL subscales (all p>0.05), depressive symptoms (p=0.78), or overall sleep quality (p=0.21). However, a greater magnitude of change in serum 25(OH)D was associated with an increased need to take medications to sleep (p for trend=0.01) and overall worse sleep quality (p for trend<0.01). Women who became vitamin D replete (≥32 ng/mL) also showed a deterioration in total sleep quality compared to women who remained <32 ng/mL despite supplementation, even after adjusting for relevant covariates (p<0.01). 

Graph depicting twelve month change in needing medications to sleep and the Pittsburgh Sleep Quality Index according to tertile of change in circulating vitamin D among women randomized to receive 2000 IU/day vitamin D.
12-month change in needing medications to sleep and the Pittsburgh Sleep Quality Index (PSQI) according to tertile of change in circulating 25(OH)D among women randomized to receive 2000 IU/day vitamin D.

Dr. McTiernan describes the main contribution of this study, “It shows what vitamin D does not do. That is, it had no significant effect on most of the dimensions of quality of life that we measured, and worsened sleep quality. Clearly, vitamin D is not a way to cure all that bothers you.”

Furthermore Dr. McTiernan notes, “In observational studies, vitamin D has been associated with many types of health indicators, and most studies find benefit (although some of that could be publication bias). The benefit of conducting randomized controlled trials, which is what ours was, is that there is much less chance of bias. So in observational studies, an association between vitamin D blood levels and a health outcome could just be due to more sun exposure (such as with exercise outdoors).”

Dr. Mason describes plans for future directions,  “Studies using objective (rather than self-reported) measures of sleep quality would be valuable for understanding the effects of vitamin D supplementation in postmenopausal women.” Dr. McTiernan adds, “All of the women in our study were overweight or obese and were on a weight loss program. It would be good to look at the effect of vitamin D on quality of life and sleep in persons who are not trying to lose weight. Also it would be good to test in men, in lighter-weight women, in persons from different races and ethnicities, and in younger individuals.”

Funding for this study was provided by the Susan G. Komen for the Cure Scientific Advisory Council Award, the National Cancer Institute, and a grant from the Breast Cancer Research Foundation.


Mason C, De Dieu Tapsoba J, Duggan C, Imayama I, Wang CY, Korde L, McTiernan A. 2016. Repletion of vitamin D associated with deterioration of sleep quality among postmenopausal women. Prev Med. 93: 166-170.