Now is the time for low vitamin D

A new study – the largest of its kind – has found that vitamin D levels are at their lowest point in spring, and take longer to go back up than previously thought.

Above: Professor Steven Boyages.

By Stephen Easton

Vitamin D deficiency affects more Australians and lasts longer than previously believed, according to the nation’s largest ever study of how well we keep up our levels of the key nutrient.

The University of Sydney study of vitamin D levels in 24,000 blood samples from a wide cross-section of New South Wales residents, over two years, also confirms that levels of the key nutrient are lowest around this time of year.

The researchers found that vitamin D levels peaked in summer, reaching a maximum in January for women and February for men, before declining gradually in late summer and falling sharply in the winter months. 

They reached their lowest point in early spring, not in winter as previously thought, but current testing guidelines do not take seasonal variation into account. 

Clinical Professor Steven Boyages, the endocrinologist who conducted the study with PhD student Kellie Bilinski, said their results suggested that current guidelines for both vitamin D testing and the use of supplements should to be reviewed.

“Ideally, testing would occur in spring when vitamin D levels reach their lowest concentration,” Professor Boyages said. “If an individual is found to be deficient, a subsequent test three months afterwards would see if they have been able to replenish their vitamin D.

“Similarly, use of vitamin D supplements currently fail to address this factor of seasonal variation. 

“A modified approach would see the use of supplements commence, or increase, at the end of summer and be maintained until the end of spring when they would either be stopped or reduced depending on an individual’s sunlight exposure.” 

The study also found that a larger number of people suffer from low vitamin D, and that it takes longer for levels to pick up again, than previously thought.

Professor Boyages said the results reinforced that older people were at a higher risk of vitamin D deficiency, as were hospital inpatients, people who live in metropolitan areas and people of lower socioeconomic status.

“We confirmed that the older age group was at risk [of vitamin D deficiency. As you would expect, they’re less ambulant, less likely to be outside, less likely to be exposed to sunlight, they have a range of other comorbidities and usually, their nutrition is poorer. All of which means they’re predisposed to vitamin D deficiency.

“… The impact is not just on bones, but also muscle strength, and probably – there’s some research to suggest it – it has an impact on cognition and even on mood, contributing to things like depression.” 

The research paper has been published in the journal Clinical Endocrinology.

Tags: sun, vitamin-d,

Leave a Reply

Your email address will not be published. Required fields are marked *