Writing in the journal BMC Public Health, the team behind the study warn that vitamin D levels in most occupational groups are well below those considered optimal for health.
Shift workers, healthcare workers and indoor workers are at a particularly high risk of deficiency, say researchers led by Dr Sebastian Straube at the University of Alberta, Canada.
"Our results suggest that occupation is a major factor that may contribute to suboptimal vitamin D levels,” said Straube. “Regular screening of vitamin D levels in at-risk groups should be considered for future clinical practice guidelines and public health initiatives.”
He added that workplace wellness programs could include education about the importance of adequate vitamin D levels – which could help prevent adverse health outcomes linked to vitamin D deficiency, including metabolic disorders, psychiatric and cardiovascular disorders, and cancer.
“We are unaware of any current guidelines on screening for vitamin D deficiency or vitamin D supplementation, which include specific guidance for workers, or risk stratification elements based on occupational factors,” wrote the Canadian team – noting that the new paper aims to address these gaps.
Vitamin D study
Straube and colleagues conducted a systematic review of 71 peer-reviewed journal articles which involved 53,425 individuals in total and spanned a range of latitudes in both the Northern and Southern hemisphere.
“We included studies where a distinct group of workers was compared with one or more groups of other workers or non-working individuals, and studies on students provided they were students of a specific vocation (e.g. healthcare students). Otherwise, we excluded studies on students,” wrote the authors.
Also excluded were research papers on subjects in the military, professional athletes, and astronauts, plus studies taking place in Antarctica, “because they were deemed less relevant to our study objective.”
The team reported prevalence of vitamin D deficiency was highest among shift workers (80% of individuals), followed by indoor workers (77%) and healthcare students (72%).
A high percentage of indoor workers (91%) were also found to have insufficient vitamin D, which means that their levels of vitamin D weren't necessarily as low as those found in vitamin D deficient individuals, but lower than levels recommended for health.
The findings of the new study could help better target testing, and improve health promotion and preventive efforts in at risk groups, said the Canadian team.
“The global prevalence of vitamin D deficiency has reached an alarming proportion.”
“Some workers should be considered an at-risk group for vitamin D deficiency,” added the authors. “Guidelines on screening for vitamin D deficiency and supplementation strategies in vulnerable groups should include consideration of occupation.”
The findings may also have implications for a number of long term nutritional studies and short term clinical trials that use medical professionals and trainees as the sample population – such as the Nurses Health Study (NHS).
“The assumption that trainees in the health care disciplines represent a convenience sample of ‘healthy’ adults may not always be true,” said the team.
Indeed, among healthcare workers, rates of vitamin D deficiency varied depending on whether they were students, medical residents (65%), practicing physicians (46%), nurses (43%) or other healthcare professionals (43%).
"Vitamin D production by the body is reliant on sunshine and UV exposure so any activity that reduces exposure tends to reduce vitamin D levels. Sunlight deprivation in young medical professionals, who may have particularly long working hours, and other indoor workers, puts them at higher risk of both vitamin D insufficiency and deficiency,” said Straube.