Low vitamin D ups the risk of early death

4 minute read

Experts are calling for proactive monitoring in vulnerable patients and elderly people to boost their health before it's too late.

Severe vitamin D deficiency increases the risk of dying early, an Australian study has found. 

According to findings from the 14-year study, people with severe vitamin D deficiency (less than 25nmol/L) were more than a third more likely to have died over the course of the study compared with people with vitamin D levels of 50mmol/L. 

“The fully adjusted odds of all-cause mortality were 36% higher for participants at 25nmol/L compared with 50nmol/L,” the study authors from the University of South Australia wrote in the Annals of Internal Medicine

The study analysed the association of 25-(OH)D serum concentrations with deaths from all-cause, cancer, cardiovascular disease and respiratory mortality among more than 300,000 white European participants of the UK Biobank. 

They found that after a 14-year follow-up, the odds of dying early rose across all four outcomes in people with severe vitamin D deficiency. 

As vitamin D levels rose the risk of death decreased steeply up until 50nmol/L. Beyond 50nmol/L the association between vitamin D levels and mortality became less significant, and there was little to no further reduction in mortality with vitamin D values of 75 to 125nmol/L, the researchers said. 

First author and UniSA PhD candidate Joshua Sutherland said the study provided further evidence for the important connection between low levels of vitamin D and mortality.  

In particular, the study highlights the risk of severe vitamin D deficiency in at-risk groups, the nutritionist told TMR

“That is, those who are vulnerable, those who are elderly, those who are not being able to get outside and people who have darker skin who are not getting out in the sun. 

Professor Elina Hyppönen, the study’s senior investigator, said public health efforts were important to ensure vulnerable and elderly people maintained sufficient vitamin D levels.  

“The key is in the prevention. It is not good enough to think about vitamin D deficiency when already facing life-challenging situations, when early action could make all the difference,” the professor in nutritional and genetic epidemiology said. 

Clinical endocrinologist Professor Jenny Gunton said that while the study used UK data, the findings could be applied to Australia. 

“The assay numbers are the same and the data is very comparable with Australia,” Professor Gunton, who was not involved in the study, told TMR.  

“The only caveat is the lack of non-white people in the study, but the relationship is likely to hold true for everybody, but people with darker skin are more likely to be deficient.” 

Professor Gunton said the study’s 14-year follow-up period decreased the possibility that the finding was skewed by including terminally ill people whose vitamin D exposure was likely to be significantly restricted.  

“Having that really long follow-up makes it much more likely that it’s not confounded by being really sick at the beginning of the study,” the head of the centre for diabetes, obesity and endocrinology at the Westmead Institute for Medical Research said.  

Professor Gunton said previous studies had shown that low vitamin D levels were associated with poor muscle function and repair from injury, increased risk of fractures, lower immune function and a higher risk of dying from respiratory illnesses. 

Professor Gunton said asking someone how much time they spent in the sun would give clinicians a good indication of whether they were vitamin D deficient.  

“If someone has dark skin, or if they have low sun exposure, I think you should recommend that they either find foods that have added vitamin D or just take a supplement,” she said. 

“The non-prescription supplements are extremely safe. Most people will need 1000 or 2000 units a day to get up to normal.” 

Professor Gunton said about 30% of normal healthy Australians were vitamin D deficient, as were 44% of women with gestational diabetes, 65% of people with type 2 diabetes and more than 80% of people who lived in nursing homes, if they were not taking supplements. 

“And most people got a lot less sun exposure since COVID. All of those numbers were pre-covid, and I would speculate that they’re likely to be much worse now. 

Annals of Internal Medicine 2022, online 25 October  

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