By Craig Weatherby
Sleep deprivation is at epidemic levels in the U.S. … and worldwide as well.
There’s considerable evidence that lack of sleep promotes major health problems, including cardiovascular disease, depression, and obesity.
To the extent that seasonal affective disorder (SAD) disrupts sleep patterns, light therapy usually helps (Pail G et al. 2011) ... and vitamin D supplements may help, too (Stumpf WE et al. 1989; Gloth FM 3rd et al. 1999).
Lack of nighttime sleep leads to daytime drowsiness … and there’s growing evidence that vitamin D deficiency can cause or worsen the situation.
Study links daytime sleepiness to low vitamin D levels
A clinical study linked, for the first time, daytime sleepiness to low levels of vitamin D (McCarty DE et al. 2012).
The credibility of the correlation was bolstered by the fact that daytime sleepiness was greatest in those with the lowest vitamin D levels … and vice versa.
A team from Louisiana State University Health Sciences Center recruited 81 people diagnosed with a sleep disorder – mostly obstructive sleep apnea – at the LSUHSC sleep clinic.
The volunteers’ vitamin D blood levels were measured, and the extent of their daytime sleepiness was determined using a standard test (Epworth Sleepiness Scale).
The Louisiana State team found that in patients without vitamin D deficiency, sleepiness scores rose as vitamin D levels fell.
Among the patients who were vitamin D deficient (defined as lower than 20 ng/mL), sleepiness was directly correlated with vitamin D levels … but only in black people, not white.
The authors believe that this makes some sense because – compared with light skin – dark skin blocks more of the UV sunrays needed to produce vitamin D in the body.
(Frankly, that’s an odd interpretation of the skin-color-based finding, since the correlation was not seen in white subjects who were equally vitamin D deficient, despite having light skin.)
The study could not determine whether vitamin D deficiency alone causes daytime drowsiness.
However, research from the authors and other teams suggests that low levels of vitamin D may promote daytime drowsiness … directly or by promoting or exacerbating chronic pain (Huang W et al. 2012).
It seems that daytime alertness can now join the many good reasons to ensure vitamin D adequacy.
You can best do that by eating fatty fish, taking supplements, and getting adequate (not excessive) exposure to UV sunrays.
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