Feeling sleepy during the day can be a sign of vitamin D deficiency, research finds.
The lower people’s vitamin levels are, the more sleepy they feel during the day.
Around half the world’s population is deficient in vitamin D.
Vitamin D deficiency can affect both sleep quality and quantity.
People with low levels of vitamin D can experience more waking during the night and less sleep overall.
The study involved 81 people who were complaining of sleep problems.
Blood sampling revealed that those with low vitamin D levels had more daytime sleepiness.
Black people are at particular risk of vitamin D deficiency because vitamin D is produced by the body in response to sunlight.
Darker skins, though, can block this action.
Vitamin D is critical to the functioning of the whole body.
From October to March many people in northern climes do not get enough vitamin D.
Vitamin D is found in oily fish, egg yolks, fortified cereals and some margarine spreads.
Most people need around 10 micrograms per day, which can also be obtained from supplements.
Dr David McCarty, the study’s first author, said:
“While we found a significant correlation between vitamin D and sleepiness, the relationship appears to be more complex than we had originally thought.
It’s important to now do a follow-up study and look deeper into this correlation.”
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The study was published in the Journal of Clinical Sleep Medicine (McCarthy et al., 2012).