“To be, or not to be, that is the question:
Whether ’tis nobler in the mind to suffer
The slings and arrows of outrageous fortune,
Or to take arms against a sea of troubles,”
Hamlet, Act 3, Scene 1 by William Shakespeare
The overall aim of CARDIPP (Cardiovascular Risk in Type 2 Diabetes – A Prospective Study in Primary Care) was to identify predictors of cardiovascular disease (CVD) in middle-aged people with type 2 diabetes. In their article (summarised alongside), Samefors and colleagues report on the association between vitamin D levels and CV morbidity and mortality in this community-based cohort study.
In Sweden, 761 people with type 2 diabetes, who were not receiving vitamin D supplementation, were recruited from 222 primary care centres. The cohort had serum 25-hydroxyvitamin D3 levels and all the main known CVD risk factors measured at baseline. Vitamin D3 levels were divided into quartiles.
Over a mean follow-up of 7.3 years, compared with the highest quartile, the lowest quartile of vitamin D3 was associated with a hazard ratio (HR) for CV morbidity and mortality of 3.46, while the second-lowest had an HR of 2.26. The HR for quartile 3 was not significant, at 1.62. Statistical significance was maintained after adjustment for the other main CVD risk factors, including physical activity, statin use, smoking, BMI, age, gender and season.
The authors calculated that, after adjustment for age, gender and season, each 20-nmol/L increase in vitamin D3 level was associated with a 37% reduction in the risk of CV morbidity and mortality. One could, therefore, argue that increasing vitamin D3 levels by 20 nmol/L would produce a similar benefit to that of statins. Intriguingly, in a recent, albeit small and uncontrolled, study of 146 statin-intolerant people, 88% of the participants had no muscle side effects when given vitamin D supplementation (Khayznikov et al, 2015).
I think Hamlet had it easy, as he was only contemplating his own actions in his existentialist angst. As healthcare professionals, we still have no clear answer to the question of whether to prescribe vitamin D supplements. This research certainly shows that low vitamin D levels are associated with CV morbidity and mortality. However, there is no compelling body of evidence to suggest that supplementation would reduce CV risk. The dilemma remains. Personally, I am of the opinion that ‘tis not nobler in the heart to suffer, and I choose to take arms [with vitamin D3] against a sea of troubles. And do get out into the sunlight – often but safely.
To read the article summaries, please download the PDF