A netizen posted that they "always can't get enough sleep, sleeping 8 hours on weekdays and 12 hours on weekends but still not feeling rested." After hearing someone mention "it might be a lack of vitamin D," they went to the hospital for a check-up. The result showed that their total 25-hydroxyvitamin D[25(OH)D] level was only 5.52ng/mL (normally this value should be ≥20ng/mL).
Does a lack of vitamin D lead to not getting enough sleep?
Vitamin D plays a crucial role in the body by promoting the absorption of calcium in the intestines, which is essential for bone health. It is a type of fat-soluble vitamin that also regulates many other cellular functions in the body.
According to the "Chinese Dietary Reference Intakes for Residents," individuals aged 0-64 are recommended to consume 400 IU of vitamin D daily (IU stands for International Units, and 400 IU of vitamin D is equivalent to 0.01 milligrams).
When we undergo medical tests, the levels of 25-hydroxyvitamin D [25(OH)D] in the blood are typically checked. As per the regulations outlined in the Chinese health industry standard (WS/T) "Screening Method for Vitamin D Deficiency in the Population," a 25(OH)D level above 20 ng/L indicates a normal vitamin D nutritional status, while levels below 12 ng/L signify a deficiency.
"Methods for Screening Vitamin D Deficiency in Populations"
Vitamin D deficiency can lead to osteoporosis, a major health concern. The individual mentioned at the beginning of the article experiencing leg cramps may be related to a lack of vitamin D.
But does vitamin D deficiency cause sleep problems?
Is always feeling "not well-rested" due to a lack of vitamin D?
For individuals who always feel sleep-deprived, their sleep may likely be categorized as "nonrestorative sleep (NRS)."
In 1987, the American Psychiatric Association first classified "nonrestorative sleep" as a type of insomnia symptom, characterized by feelings of unrestful sleep, light sleep, or poor sleep quality, even if the duration of sleep may seem normal.
The causes of nonrestorative sleep are complex, involving psychological factors such as emotional disorders, as well as lifestyle habits including alcohol, tobacco, caffeine intake, and other behaviors related to poor sleep hygiene. However, there is no clear evidence to suggest that a lack of vitamin D is a primary cause of feeling "not well-rested."
Regarding other types of insomnia symptoms, some studies have found a connection between vitamin D deficiency and insomnia or poor sleep quality. For instance, research has shown that serum vitamin D levels are significantly lower in chronic insomnia patients compared to healthy individuals. Nevertheless, these findings are not consistent.
In 2021, a clinical randomized controlled study in Norway supplemented 189 individuals with vitamin D deficiency for 4 months, but the results showed that vitamin D supplementation did not significantly improve sleep levels.
In 2022, a systematic review and meta-analysis examined the impact of vitamin D supplementation on sleep quality, incorporating a total of 19 studies, including 13 randomized controlled trials. The results indicated a certain association between vitamin D supplementation and a decrease in sleep index compared to the placebo group, but the evidence quality was only moderate. Additionally, the effects of vitamin D supplementation on sleep difficulties and disorders were inconsistent. Therefore, researchers believe that further studies are needed to understand the impact of vitamin D supplementation on sleep.
Overall, while there is a certain association between vitamin D deficiency and sleep disturbances, supplementing vitamin D does not directly prevent or treat sleep disorders.
How to Improve Sleep?
There are many complex factors that influence sleep, but in terms of diet and lifestyle, it is recommended to focus on the following aspects:
Maintain a diverse and balanced diet. Research suggests that a balanced diet and nutrition are beneficial for overall health and can contribute to better sleep.
Have a light dinner and avoid consuming too many spicy or stimulating foods. Excessive intake of oil, salt, and fat, along with insufficient vegetable consumption, can lead to insomnia. Spicy foods can irritate the stomach and affect sleep.
Avoid eating too late. Eating late, especially close to bedtime, can hinder digestion and negatively impact sleep. It is advisable not to eat anything within three hours before bedtime.
Don't go to bed hungry. Going to bed hungry can disrupt sleep. If feeling hungry before bed, opt for starchy foods like oatmeal or millet porridge.
Avoid vigorous exercise before bedtime. Moderate exercise before bed can reduce light sleep, increase deep sleep, ensure sleep continuity, and enhance sleep efficiency. However, avoid overly strenuous activities.
Limit water intake before bed. Drinking too much water can lead to frequent bathroom trips, disrupting sleep.
Avoid smoking, alcohol, and caffeine-containing foods before bed. Alcohol can affect sleep quality, while smoking can increase alertness, making it harder to fall asleep. Some individuals are sensitive to caffeine, so it's best to avoid caffeine-containing foods and beverages like coffee, tea, milk tea, cola, chocolate, as well as products containing guarana or yerba mate extracts, which also contain caffeine.
How to Supplement Vitamin D?
Although supplementing vitamin D may not directly address sleep issues, it remains crucial for overall health.
Humans primarily obtain vitamin D through two main pathways: exposure of the skin to ultraviolet rays from sunlight, leading to the synthesis of vitamin D, and through dietary intake. Animal-based foods rich in vitamin D include dairy products, salmon, mackerel, and sardines.
To increase vitamin D levels, it is essential to engage in outdoor activities. Sun exposure for about 10-20 minutes when the UV rays are not too strong can help. Additionally, consuming foods rich in vitamin D such as dairy products, salmon, mackerel, and sardines is recommended.
If concerned about insufficient vitamin D levels, vitamin D supplements can be taken. Generally, taking vitamin D supplements outweighs any potential drawbacks.
Reference:
[1] Roth T, Zammit G, Lankford A, Mayleben D, Stern T, Pitman V, Clark D, Werth JL. Nonrestorative sleep as a distinct component of insomnia. Sleep. 2010 Apr;33(4):449-58. doi: 10.1093/sleep/33.4.449. PMID: 20394313; PMCID: PMC2849783. [2] Liu Yaping, Pan Jiyang. Research Status of Non-Restorative Sleep. Practical Medical Journal, 2012, 28(07):1208-1210.
[3] Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition)
[4] Ohayon MM. Prevalence and Correlates of Nonrestorative Sleep Complaints. Arch Intern Med. 2005;165(1):35–41. doi:10.1001/archinte.165.1.35
[5] Vitamin D. Fact Sheet for Health Professionals. NIH
