Vitamin D is important for healthy sleep in both children and adults

Lack of sleep is common among children and adults. It increases the risk of overweight, diabetes, cardiovascular diseases, blood clots, depression, infections, and a number of other diseases. Lack of vitamin D is also common, but a team of Chinese scientists have revealed that there is a link between having too little vitamin D and not being able to sleep properly and waking up feeling refreshed.

Just like healthy eating habits and exercise, sleep is important for your mood and health. Too little sleep increases your risk of impaired performance, overweight, diabetes, cardiovascular diseases, blood clots, depression, infections, and many other health problems.
In old days, it was much more common to go to bed early and get a good night’s sleep. Things have changed, however, and our modern lifestyles with electric lights and glaring screens from electronic devices get in the way of our sleep. We have difficulty with falling asleep or sleep poorly.
A new epidemiological study from Sweden has revealed that 40% of 10-year-old children sleep less than nine hours each night, which is far too little.
At the same time, we get too little direct sunlight during the daytime, which has made vitamin D deficiencies a lot more common. A British study shows that 70% of teenagers in the age group 14-16 years lack vitamin D, and a Chinese study shows that 40% of schoolchildren lack vitamin D. Just like getting too little sleep, a vitamin D deficiency increases your risk of overweight, diabetes, cardiovascular diseases, depression, infections, and many other health problems.
Only few studies show a link between lack of vitamin D in the blood and lack of sleep in older children and adults.

Too little vitamin D and lack of sleep is a serious cocktail and a global problem

Lack of sleep is a global problem, and the same goes for vitamin D deficiencies, which also affect children and youngsters.
The aim with the Chinese study was to investigate the relation between vitamin D levels in the blood and the duration of sleep. Eight hundred healthy children aged 8-14 years took part in the study. All participants were from Ningbo in the Zhejiang province, and both the children and their parents were thoroughly informed about the study.
All children were measured and weighed and questionnaires were filled in with details about the children’s health and eating habits.
The scientists took blood samples to measure levels of vitamin D in the form of 25(OH)D. Levels above 20 ng/ml (nanograms per milliliter) were considered sufficient, while levels below 20 ng/ml were considered insufficient.
At school, the children were asked to fill in a questionnaire with questions about when they got up in the morning, and when they went to bed at night. The scientists could then calculate the duration of the children’s sleep and compare it to the nine hour minimum limit, which is considered to be adequate for children of that age.

Significant link between vitamin D, sleep, and BMI

It turned out that 33 percent of the children slept too little and got less than the recommended nine hours per day. At the same time, 30 percent of the children lacked vitamin D. The scientists found a significant link between elevated BMI and getting too little sleep, lacking vitamin D, and skipping breakfast.
They did not find a significant relation in terms of gender, or the parents’ status, smoking habits or physical activities.
The scientists say that this is the first study to link levels of vitamin D in children to the duration of their sleep. The study is published in the science journal Nutrients.

Sunlight and vitamin D affect sleep in several ways

Although the link between vitamin D and the quality of sleep has not yet been mapped out, the Chinese researchers speculate in different theories. Lack of vitamin D may impair the body’s endogenous production of various substances such as melatonin, interleukins, and prostaglandins, all of which have a regulatory role. Another theory is that vitamin D receptors in the hypothalamus and other cells in the nervous system are activated by vitamin D. This theory is supported by a human study where people slept longer and better, when they were given vitamin D supplements.
The scientists also suggest that sleep problems may be related to engaging in too few outdoor activities. Sunlight is the best source of vitamin D, but people living at the northern latitudes can only synthesize the nutrient during the summer period, where the sun sits sufficiently high in the sky. Sunlight also stimulates the pineal gland’s production of the sleep hormone, melatonin, at night. That way, sunlight has a dual effect and a self-reinforcing effect on our sleep.

How much vitamin D do we need?

The reference intake for vitamin D (in Denmark) is five micrograms for children and 10 micrograms for adults. Many scientists believe that our actual need for the nutrient is a lot greater. The body can easily synthesize 30-100 micrograms of vitamin D on a hot summer’s day. In the winter period, however, a supplement is necessary, especially as a normal healthy diet and regular multivitamin pills only provide limited amounts of vitamin D.

References

Qing-Hai Gong et al. 25-Hydroxyvitamin Status and Its Association with Sleep Duration in Chinese Schoolchildren. . Nutrients 2018

Scott LaFee. Vitamin D Deficiency Linked to Greater Risk of Diabetes. UC San Diego Health. April 2018

Graven, Andreas R. Søvn påvirker vægt og aktivitetsniveau. Videnskab.dk 2014

Graven, Andreas R. For lidt søvn kan give depression. Videnskab.dk 2014