Updated review finds vitamin D has no impact on asthma control

16th February 2023

Asthma control is not improved with the use of vitamin D supplementation according to the findings of an updated Cochrane systemic review

Supplementing with vitamin D has no effect on asthma control or the risk of disease exacerbations according to the findings of an updated Cochrane systemic review.

Asthma is a chronic inflammatory respiratory disease and which globally, in 2019, was estimated to affect 262 million people in 2019, leading to 455,000 deaths. The potential role of vitamin D in asthma control is unclear though one study observed that among those deficient in the vitamin, the odds of having an exacerbation were 25% greater compared to those with levels in the normal range. Moreover, other work in children with severe, therapy-resistant asthma, found that lower vitamin D levels were linked to increased airway smooth muscle mass together with worse asthma control and lung function.

In 2016, a Cochrane review examined the possible value of vitamin D for the management of asthma and concluded that the vitamin is likely to reduce the risk of severe asthma exacerbations and healthcare. However, the authors could not determine if these benefits were confined to those who had suboptimal vitamin D levels. The current review provided an updated meta-analysis based on subsequently published trials and included patients with mild to moderate asthma.

Asthma control and vitamin D use

A total of 20 studies, 15 of which included 1,155 children and 5 with 1,070 adults were included in the updated analysis. The researchers performed several subgroup analyses based on initial vitamin D status as well as the dosage and regime of the vitamin used.

Overall, use of vitamin D did not reduce or increase the proportion of patients who experienced one or more disease exacerbations requiring treatment with systemic corticosteroids (Odds ratio, OR = 1.04, 95% CI 0.81 – 1.34). In addition, vitamin D had no effect on the rate of asthma exacerbations and subgroup analysis failed to reveal any effect based on vitamin D status, dose, dosage frequency or patient age.

Secondary outcomes examined included exacerbations leading to hospitalisation and measures of asthma control but again, vitamin D had no impact on any of the assessed outcomes.

The authors concluded that in contrast to their 2016 review, the current analysis failed to identify any benefits from vitamin D supplementation on asthma exacerbations or asthma control.

Citation
Williamson A et al. Vitamin D for the management of asthma. Cochrane Database of Systematic reviews, 2023

Analysis finds vitamin D supplementation potentially beneficial for type 2 diabetes

14th February 2023

A meta-analysis suggests that vitamin D supplementation reduces fasting plasma glucose and HbA1c levels in patients with type 2 diabetes

Vitamin D supplementation may be of value to patients with type 2 diabetes, especially if they have suboptimal levels of the vitamin according to a meta-analysis undertaken by US and Iranian researchers.

It has been estimated that in 2017, a staggering 462 million individuals had type 2 diabetes, corresponding to just over 6% of the global population. While there are several therapies available for the management of type 2 diabetes, new treatments will always be needed, given the high prevalence of the disorder. One such potential treatment is vitamin D supplementation and while this is usually given to regulate calcium and phosphorus levels, in recent years, a purported role has been suggested for several diseases. For example, data from the prospective Nurses’ Health study found that higher vitamin D and calcium intake was associated with a 33% lower risk of type 2 diabetes. Nevertheless, studies that involved actual vitamin D supplementation produced mixed findings. For example, one study 6-month trial found that supplementing with the vitamin in patients with type 2 diabetes, failed to affect either insulin sensitivity or secretion. In contrast, an 8-week intervention study demonstrated significant reductions in fasting plasma glucose, insulin and HOMA-IR.

As a result, in the current study, researchers performed a meta-analysis to examine the effect of using the vitamin on indices of glycaemic control including fasting plasma glucose (FPG), HbA1c and HOMA-IR.

Vitamin D supplementation and glycaemic measures

A total of 46 eligible trials were identified including 4,313 patients with type 2 diabetes and a mean age of 56.5 years and of whom 2,164 received the vitamin intervention. The majority of the studies (42) used an oral supplement, whereas in four trials, it was given via intramuscular injection.

The pooled analysis for HbA1c showed a significant reduction compared to placebo for vitamin D (weighted mean difference, WMD = -0.20, p < 0.001). Similarly, there was a significant reduction in FPG (WMD = -0.28 mmol/L, p < 0.001) and HOMA-IR (WMD = -0.42, p = 0.019) in those given vitamin D.

The authors concluded that although vitamin D supplementation had a positive impact of glycaemic indices, they cautioned that the substantial heterogeneity between the included studies, raised the possibility of publication bias.

Citation
Farahmand MA et al. What is the impact of vitamin D supplementation on glycemic control in people with type-2 diabetes: a systematic review and meta-analysis of randomized controlled trails. BMC Endocr Disord 2023