In 2009 researchers discovered that low levels of vitamin D were associated with an increased risk of getting less than five hours of sleep. The study found that participants with low levels of vitamin D tended to find it more difficult to fall asleep compared to those with higher levels of vitamin D.
Although the study’s authors said the role of vitamin D in the reduction of sleep time remained unclear, they suggested that low levels of vitamin D may reduce melatonin production and alter the sleep-wake cycle.
Since vitamin D levels are typically lower among the elderly due to skin aging and more time spent indoors, researchers conducted a study to examine whether levels of vitamin D were associated with objective sleep measures among community-dwelling older men. Their findings were published in 2015 in the journal SLEEP.
The study involved 2,966 men over the age of 68. Researchers took blood samples from participants to measure vitamin D levels. Objective sleep data was collected using wrist actigraphy and measured total sleep duration, sleep efficiency, and the amount of time spent awake during the night. The sleep trackers were worn for an average of five consecutive 24 hour periods.
Researchers found that there was a significant link between lower levels of vitamin D and short sleep duration (less than five hours of sleep), poorer sleep efficiency, and more sleep fragmentation. In fact, those with the lowest levels of vitamin D (less than 20 ng/mL) had double the risk of getting less than five hours of sleep compared to those with the highest levels of vitamin D (more than 40 ng/mL).
Why and how does vitamin D affect sleep?
We still don’t know for sure. The study’s authors pointed to previous research that linked low levels of vitamin D with a number of factors that can harm sleep such as pain, muscular problems, immune issues, and heart disease. With that being said, low levels of vitamin D may not be to blame for these types of conditions — the conditions themselves may lead to low levels of vitamin D, perhaps due to lower levels of physical activity and less sun exposure.
Can vitamin D supplements improve my sleep?
The authors of this study reported that there was a nonsignificant suggestion that the strongest links between vitamin D and sleep were found in those who took vitamin D supplements — and previous research has linked higher levels of supplemental vitamin D with improved sleep. One study in particular found that individuals who took either 1,200 IU/day or 50,000 IU/week of vitamin D fell asleep faster and slept for longer.
But we still don’t know whether vitamin D supplements improve sleep. It may simply be the case that those who take vitamin D supplements have other health habits that lead to better sleep.
Vitamin D supplement advice
If you decide to take vitamin D supplements, there are a few things you should be aware of:
- According to the FDA, the daily recommended amount of vitamin D is 800 IU/day (20 mcg per day).
- The upper limit for vitamin D is 4,000 IU/day (100 mcg per day) for children 9 years and older, adults, and pregnant and lactating teens and women.
- In the United States, vitamin supplements are not regulated. One study found vitamin D levels in supplements ranged from nine to 146 percent of the amount listed on the label — so looking for supplements that are USP verified or NSF certified may be worth the extra effort.
Alternatives to vitamin D supplements
You can increase vitamin D levels without the use of supplements by eating more fatty fish (such as salmon, tuna, and mackerel) and foods fortified with vitamin D. Increasing your exposure to sunlight can also help. Between five and 20 minutes of sun exposure between 10:00 AM and 3:00 PM at least twice a week to the face, legs, arms, or back without sunscreen usually leads to adequate vitamin D production.
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