When it comes to sleep, there’s no optimal amount of sleep that fits all. However, most adults need at least 7 hours of sleep a night. Getting less than that can lead to adverse negative effects on a person’s lifestyle and health, including cardiometabolic diseases, weakened immune responses, and impaired cognitive performance. In extreme cases, it could even cause death. Approximately 30% of adults suffer from insomnia, a sleep disorder preventing a person from falling asleep. 10% suffer from chronic insomnia. For many, a lack of sleep can seriously affect their economic, social, and family lives. It causes a general decline in the satisfaction of a person’s quality of life.
There are some studies that suggest that vitamin D can have an effect on the quality of someone’s sleep. A deficiency in vitamin D could lead to difficulties falling and staying asleep, but studies into vitamin D supplementation and its effects on sleep are lacking. Although most studies aren’t definitive – there was no direct link found between the two, nor any cause or effect named – further investigation into the use of vitamin D supplementation and whether or not it improved sleep quality was undertaken.
Who and What Was Studied?
The study conducted was a randomised controlled trial on 93 Iranians between the ages of 20 and 50. All the people included in the test suffered from lack of sleep, as defined by the Pittsburgh Sleep Quality Index (PSQI). However, the subjects were at a level of poor sleep quality that didn’t define them to have a sleeping disorder – a score of less than 5 on the PSQI questionnaire.
However, participants were removed from the study if they were smokers, took sleep medication, or already took high doses of vitamin D supplements. Anyone with health conditions that could lead to poor sleep quality were also excluded. Their sun exposure was measured at the beginning and the end of the trial by interviewing participants, and a level was estimated as a result. This included the length, body parts, and their sunscreen usage during sun exposure.
The vitamin D group received four doses of 50,000 International Units (IU) of vitamin D3 in fortnightly doses (one dose every 2 weeks). This worked out at approximately 3,571 IU per day throughout the trial.
The second group received a placebo of edible paraffin oil capsules following the same schedule. Blood tests were taken at the beginning and end of the trail to measure vitamin D levels over an eight-week period. No primary outcomes were specified for this trial.
What Were the Findings?
Vitamin D in the bloodstream was measured in nanograms/millilitre, or ng/ml. The baseline vitamin D levels were measured at the start of the trial. They were 25 ng/ml for the vitamin D group, whereas the placebo group were 27.6 ng/ml. The difference is minimal.
However, after eight weeks, the difference between them increased dramatically. The vitamin D group contained 37.7 ng/ml, whereas the placebo group remained at the same level of 27.6 ng/ml.
The results showed that the vitamin D group had improved their sleep score significantly. Their score was reduced by 2.7 points, whereas the placebo group didn’t change significantly at all.
The vitamin D group had scored significantly less in their PSQI score in several aspects. For example, there was greater sleep duration, with less time taken to fall asleep too. At the end of the study they took 33 minutes to fall asleep, with 6.5 hours sleep duration. Alternatively, the placebo group took 59 minutes to fall asleep, with around 5.2 hours sleep duration.
The sleep quality score also improved. The Vitamin D group scored 1.2, whereas the placebo group scored a 1.5 (the lower the score, the better the sleep quality). However, one aspect that didn’t change with either group was the use of sleep medication and daytime dysfunction.
The daily reported exposure to the sun for each group was the same at the start of the study too, but the vitamin D group’s sun exposure was decreased from 21 minutes a day to only 17 minutes by the end. The placebo group had no change in their sun exposure. Furthermore, time spent napping each day along with physical activity didn’t change throughout the study.
In terms of personal information, the age, sex, education, and marital status of each participant was relatively similar. Measurements taken during the trials include bodyweight, BMI, waist circumference, hip circumference, and the waist-to-hip ratio. However, there were no significant differences between the groups at the start or end of the trial.
What Does This Tell Us?
What this study tells us is that vitamin D supplementation could improve someone’s sleep quality if their sleep disruption is minor with no chronic sleep disorders or underlying medical conditions. Some studies suggest that vitamin D supplementation plateaus in its effects after some time, so further studies are required to determine the effects of vitamin D on a person’s long-term sleep quality. So, while the statistical evidence suggests a significant benefit of taking vitamin D supplements, the real world implications require further trials to be undertaken.
For example, the bigger picture includes why a person a) can’t sleep and b) whether that reason is a cause or effect of low vitamin D in the bloodstream. For example, a vitamin D deficiency could directly have an effect on the brain and certain immune functions, but it could also indirectly affect your sleep by causing other medical conditions to become prominent.
Because people with medical conditions were excluded, it might be beneficial to create studies on those with other possible causes of sleep deprivation. As a result, a better understanding of how vitamin D supplements improve sleep will become more evident.
- Vitamin D deficiency can directly and indirectly cause sleep deprivation through various methods.
- A randomised trial found that supplemental vitamin D3 improves aspects of the PSQI, improving sleep quality.
- There isn’t enough evidence to determine the long term effectiveness of supplemental vitamin D in treating minor sleep deprivation.