Sleepiness and fatigue during the day can be a sign of vitamin D deficiency, studies find.
People with lower vitamin D levels can experience less sleep overall and more waking during the night.
People experience worse sleep, the lower their vitamin D levels are.
Vitamin D may affect critical neurotransmitters and inflammatory markers.
Fatigue may also be due to problems in the body’s mitochondria.
Mitochondria are the ‘power stations’ within each cell in our body.
Without vitamin D, the mitochondria cannot work efficiently.
Around half the world’s population is deficient in vitamin D.
Foods that are rich in vitamin D include oily fish and eggs, but most people get their vitamin D from the action of sunlight on the skin.
Other signs of vitamin D deficiency include low mood, muscle fatigue, difficulties with learning and memory, gut problems and headaches.
One study of global populations has found that vitamin D deficiency is a widespread problem in many areas.
Vitamin D is vital for bone mineralisation, so deficiency can lead to a greater risk of fracture.
Some of the main risk factors for having low vitamin D levels are:
- being female,
- poor dietary habits,
- being older,
- living in northerly areas,
- and less exposure to sunlight.
Urbanisation means many people live and work indoors.
A walk of as little 20 minutes in the daylight is enough to provide sufficient levels of vitamin D.
The conclusions come from a review of the research carried out across six continents.
The results showed the risk of vitamin D deficiency is highest in the Middle East and South Asia, largely because of traditional clothing that blocks the action of sunlight on the skin.
The study was published in the journal Osteoporosis International (Mithal et al., 2009).