Our main source of Vitamin D is sunlight. When we are outside, sunlight, especially UVB is converted in the lower levels of our skin to Vitamin D. Now that British Summertime has ended with the clocks change, it instantly feels that the dark days and earlier nights of winter are upon us.
It is now more obvious that our days are shortening. The shortest day this year will, in fact, fall on Thursday 21st December 2019. At this point the sun rises at 8.03 and sets at 3.53pm in London and we get just seven hours and 49 minutes of daylight. This is a significant decrease in our opportunity to get sunlight, and therefore Vitamin D, versus the longer summer days and nights. Our longest day in mid June gets over double this level of sunlight at 16 hours and 38 minutes !
Vitamin D and sleep
Vitamin D is traditionally known for its role in bone health. Recent research has also shown a role for Vitamin D in the quality of sleep. Scientists now think Vitamin D activates receptors in the brain that are associated with sleep.
Various studies have shown that vitamin D status was positively correlated with sleep efficiency and sleep quality. https://www.ncbi.nlm.nih.gov/pubmed/22699141/
Vitamin D deficiency has also been associated with excessive daytime sleepiness as reported in the Journal of Clinical Sleep Medicine.
In addition, https://www.ncbi.nlm.nih.gov/pubmed/25581929/ suggested that low levels of total serum Vitamin D are associated with poorer sleep including short sleep duration and lower sleep efficiency.
Sunlight and our body clock
Our body clock, or circadian rhythm thrives on regularity. When we go to bed and wake up at the same time seven days a week we strengthen the body clock and thus get a better night’s sleep. Our body clock is also strengthened by the difference in intensity between light days and dark nights. In the autumn and winter days we get both a decrease in daylight hours and a decrease in light intensity in the cloudy greyer days.
Planning how to get your regular daily dose of sunlight is more important during this period. Start each day with a morning walk or run if you can. As you could be going to and from work in the dark, getting outside at lunchtime is another obvious window to get your daily dose of sun.
Vitamin D and winter blues
The decrease in natural sunlight produces a naturally lower mood in most of us. This can lead into winter blues if we aren’t mindful, and in some cases even Seasonal Affective Disorder. Seasonal Affective Disorder ( also known as SAD) is a severe depression which needs medical intervention.
With regards to winter blues however, research has shown that we often change our lifestyle in response to the colder darker winter months. It is these changes which then have more of an effect in lowering our mood than the decrease in sunlight. Not going out to socialise as much , exercising less, and eating more carbohydrate dense foods are changes many of us make during the autumn and winter https://thesleepsite.co.uk/beating-the-winter-blues/. These then lower our mood.
That said, Vitamin D supplementation has been shown to relieve depression when levels in the body are low.
Which foods are best to get Vitamin D naturally ?
Make sure you have a varied diet in the winter which contains foods rich in Vitamin D. This can help compensate for the decrease in sunlight. Foods which contain Vitamin D naturally tend to be from animal sources. These include eggs, dairy products, meat and especially oily fish such as salmon and sardines. Vitamin D is also included in commercially made products, being fortified in some breakfast cereals for example. For vegetarians, mushrooms are a good source of Vitamin D.
Who should take Vitamin D supplements ?
Public Health England recommends that with the decrease in sunlight through the autumn and winter everyone should consider taking a daily supplement containing 10 µg of vitamin D. The NHS recommends that sun-deprived elderly people and breast feeding women should take vitamin D supplements. Very young children aged six months to five years too.
When is the best time to take Vitamin D supplements ?
Vitamin D is a fat-soluble vitamin. Research suggests that it is best absorbed when taken alongside a meal which contains fat too. With regards to time to take, anecdotal reports suggest that you should avoid taking at night as this could interfere with your sleep.
The rule of thumb with any supplements is to take them at the same time every day as part of a daily health routine. The best form of Vitamin D to take is a form called Vitamin D3. Always consult your G.P. though if you are on medication.