Nutritionist’s take: Check thyroid, vitamin D, magnesium, ferritin and iron levels, and if snoring is a problem, do sleep apnea screening.

​Studies support Dr. Fernando’s claims. Multiple studies link low vitamin D with poorer sleep duration, lower sleep efficiency, and increased daytime sleepiness. A 2018 systematic review found that vitamin D deficiency was significantly associated with higher odds of sleep disorders, particularly insomnia and fragmented sleep.