Zinc's Link to Sleep Quality Remains Unclear, Further Studies Needed

Sleep quality could stand to benefit from zinc supplements, according to a recent systematic review published in Health Science Reports. However, despite these suggested benefits, there are still a lot of unexplored data on this subject that could help researchers make more definitive conclusions about zinc intake and its impact on sleep.¹

Zinc may help individuals get better sleep, but research in this area provides mixed conclusions | image credit: airborne77 - stock.adobe.com

The human body does not produce zinc naturally; therefore, it must be included in the diet or acquired through supplements.² Zinc plays an important role in several bodily processes, including immune system functioning, gene expression, metabolism, nerve function, digestion, skin health, wound healing, general development and growth, cell division, and more. As such, zinc deficiency can lead to an array of complications from skin rashes and behavioral issues to developmental delays or impairments, among others. Although the benefits of zinc are well documented for an array of bodily functions, the present authors note that the effect of zinc on sleep quality has yet to be sufficiently studied.¹

To paint a clearer picture, researchers searched the Medline, Web of Science, Scopus, and Google Scholar databases to narrow down randomized control trials that focused on zinc supplementation and sleep quality. The Cochrane Interventional Article Quality Assessment Tool was applied to evaluate the risk of bias in identified studies to ensure they were presenting quality data.

Eight studies were eligible for this review, which included 9 study arms. These data spanned from 2009 to 2022, featuring studies conducted in Iran (n = 5), Spain, South Korea, and the US. There were 5 studies that used single-therapy approaches, and 3 that utilized combination therapy. All age groups, from infants to older adults, were included in this research and interventions ranged from 4 to 48 weeks. The daily dosage of zinc supplementation fell anywhere between 10 mg/day to over 73 mg/day.

The Pittsburgh Sleep Quality Index measured the impact of zinc on sleep in 5 studies. Two of these studies, from Afzali et al³ and Haddadian-Khouzani et al,⁴ found significant correlations between a zinc dose of 30 mg/day and improved sleep for adults at 10 and 12 weeks, respectively, compared with a control group and placebo (P < .05). A study by Gholipour Baradari et al⁵ also suggested a significant improvement in sleep quality, as it measured outcomes in intensive care unit nurses who received 220 mg every 72 hours compared with controls; however, no significant differences were observed between groups when it came to sleep duration. Ranjbar et al,⁶ in a similar thread, did not observe significant changes in sleep duration for patients with major depression (receiving 25 mg/day of zinc) and controls.

However, research conducted by Castro-Marrero et al,⁷ which included patients with myalgic encephalomyelitis/chronic fatigue syndrome, did not witness any significant improvements for sleep with a combination therapy of zinc (10 mg/day) and melatonin (10 mg/day). Another study by Jafari et al⁸ similarly did not find any significant associations between daily zinc (30 mg/day) over 12 weeks in women with premenstrual syndrome.

A 2-phase study conducted by Kordas et al⁹ had inconclusive findings on the impact of zinc in infants. In one phase, Nepalian infants were able to sleep longer after zinc supplementation compared with controls; in the other phase, Zanzibarian infants did not appear to derive significant benefits.

Considering their findings, the authors hailed their research as the first of its kind to truly focus on the impact of zinc supplements on sleep quality. Yet, they felt somewhat limited by the small sample sizes they included, as well as the immense diversity of these groups that could impact the study’s generalizability.

“However, more research, primarily clinical trials, is needed to clarify the beneficial effects of zinc supplementation on sleep quality with consideration of dietary zinc intake and the recommended dietary allowances of zinc in the different populations. It is also recommended to investigate the effect of zinc supplementation on sleep quality in people with zinc deficiency in future studies,” they concluded.

References

1. Jazinaki MS, Gheflati A, Moghadam MRSF, et al. Effects of zinc supplementation on sleep quality in humans: A systematic review of randomized controlled trials. Health Sci Rep. 2024;7(10):e70019. doi:10.1002/hsr2.70019

2. Kubala J. Zinc: everything you need to know. Healthline. Updated November 28, 2022. Accessed October 8, 2024. https://www.healthline.com/nutrition/zinc

3. Afzali A, Mojarrad LM, Goli S, Bagheri H, Mirhosseini S, Ebrahimi H. Effect of zinc supplement on sleep quality in older adults: a randomized clinical trial study. Acta Facul Med Nais. 2022;39(2):185-197. doi:10.5937/afmnai39-33101

4. Haddadian-Khouzani S, Shahidi S, Askari G, Clark CCT, Rouhani MH. The efficacy and safety of zinc gluconate supplementation on quality of life, sleep quality, and serum albumin in hemodialysis patients: a randomized clinical trial. Euro J Integr Med. 2022;55:102183. doi:10.1016/j.eujim.2022.102183

5. Gholipour Baradari A, Alipour A, Mahdavi A, Sharifi H, Nouraei SM, Emami Zeydi A. The effect of zinc supplementation on sleep quality of ICU nurses: a double blinded randomized controlled trial. Workp Health Saf. 2018;66(4):191-200. doi:10.1177/2165079917734880

6. Ranjbar E, Kasaei MS, Mohammad-Shirazi M, et al. Effects of zinc supplementation in patients with major depression: a randomized clinical trial. Iran J Psychiatry. 2013;8(2):73-79.

7. Castro-Marrero J, Zaragozá MC, López-Vílchez I, et al. Effect of melatonin plus zinc supplementation on fatigue perception in myalgic encephalomyelitis/chronic fatigue syndrome: a randomized, double-blind, placebo-controlled trial. Antioxidants (Basel). 2021;10(7):1010. doi:10.3390/antiox10071010

8. Jafari F, Tarrahi MJ, Farhang A, Amani R. Effect of zinc supplementation on quality of life and sleep quality in young women with premenstrual syndrome: a randomized, double-blind, placebo-controlled trial. Arch Gynecol Obstet. 2020;302(3):657-664. doi:10.1007/s00404-020-05628-w

9. Kordas K, Siegel EH, Olney DK, et al. The effects of iron and/or zinc supplementation on maternal reports of sleep in infants from Nepal and Zanzibar. J Dev Behav Pediatr. 2009;30(2):131-139. doi:10.1097/DBP.0b013e31819e6a48