People living in Scotland 400 hundred years apart have been shown to suffer similar seasonal declines over winter in their vitamin D levels despite the enormous changes in lifestyle and diet over the intervening period.
Archaeologists and nutrition scientists from the University of Aberdeen have teamed up with researchers from Ireland’s Atlantic Technological University and Boise State University (USA) to examine the long-term impact of living in a region with low levels of winter sunlight.
Their findings, published in the Nature journal Scientific Reports, were obtained using a new method to detect vitamin D in human hair samples – the first time it has been applied to archaeological remains.
The researchers compared vitamin D levels in the hair of volunteers who have been living in the Aberdeen area for at least two and a half years to those analysed in a rare specimen of preserved hair from a burial previously excavated from St Nicholas Kirk, estimated to have lived in the city in the 16th or 17th century.
Vitamin D is essential for healthy skeletal growth and is increasingly recognised for its role in chronic disease development, inflammation and immunity. But in Scotland the sunshine is only strong enough to allow our bodies to produce our own vitamin D between April and September.
In addition to hours spent outside, vitamin D levels can be increased through diet such as oily fish and supplementation.
Archaeologist Kate Britton, who led the research team which included early career scientists Orsolya Czére and Eléa Gutierrez, said a clear seasonal variation could be detected in both modern and historical hair samples.
She said: “We might expect that with modern methods to enhance our vitamin D intake through diet and supplementation this seasonal variation would be less significant.
“In recent years there have been wide-spread health promotions around the benefits of supplementing with vitamin D during winter.
“Similarly, we could reasonably expect that medieval population is likely to have spent a greater proportion outside and that those living in coastal areas like Aberdeen in the past may have consumed a greater proportion of their diet from local sources such a fish.
“But what this unique study has shown is that levels in many of our modern participants were similar to those of our archaeological sample, and that levels were consistently higher in summer and lower in winter in people who lived in the same city 400 years apart.”
The study is a global first in applying a new technique to measure vitamin D using hair in an ancient specimen and it opens a new window into the lives of those living in the past.
“In archaeology a lack of vitamin D is usually identified through skeletal manifestations such as rickets but that only informs us about the most extreme deficiencies and cannot be quantified,” Professor Britton added.
“Using hair in this way is a significant step forward in the growing field of metabolomics in archaeological science.
“If we can measure something such as vitamin D then we might also be able to use these state-of-the-art techniques to look at other aspects of health in the past through hair, such as stress levels, or even drug use of previous populations.”
The study also suggests that examining vitamin D through hair rather than blood offers potential benefits for understanding health today.
As hair grows around a centimetre each year, scientists can detect changes over multiple months rather than taking a snapshot in time as might be obtained through a blood sample taken in a medical setting.
Professor Baukje de Roos, a nutrition scientist from the Rowett Institute at the University of Aberdeen who was responsible for collecting hair samples from modern participants, and with Gary Duncan carried out the vitamin D analysis in hair, said: “Our findings also support previous research which has shown than weight loss can mobilise vitamin D from adipose fat and significantly increase vitamin D levels in our blood, and in hair.
“It is important that we gain a greater understanding of how vitamin D in hair compares to vitamin D levels in blood, which is currently used to assess vitamin D deficiency globally.
“The method to measure vitamin D in hair opens new opportunities to more easily monitor and understand how diet, supplementation or weight loss affects our vitamin D levels across the seasons and in different settings. This could help health professionals to provide better guidance and recommendations in the ways we can best support vitamin D and health.”