Published in Nutrition Reviews, the meta-analysis of 20 randomised controlled trials (RCTs) revealed lower levels of three inflammatory markers in patients with type 2 diabetes (T2D) who were supplemented with vitamin D, found the research team from Monash University, Melbourne.
Compared with controls, vitamin-D supplemented patients had lower levels of C-reactive protein (CRP), tumour necrosis factor-alpha (TNFA) and erythrocyte sedimentation rate (ESR). The researchers also found higher levels of the hormone leptin, which works to suppress hunger.
“Our systematic review and meta-analysis showed that in patients with T2D, vitamin D supplementation results in a modest decrease several markers of inflammation and increase in leptin levels,” commented senior researcher Associate Professor Barbora de Courten.
Significance
Previous intervention studies have shown conflicting results as to whether vitamin D supplementation could improve inflammation in T2D patients. This review, bringing together all existing RCT evidence, would help address the lack of consensus and knowledge gap, suggested the researchers.
“This is the first ever systematic review and meta-analysis on this topic in patients with T2D,” said Associate Professor de Courten.
Chronic low-grade inflammation is widely known to be present in, and precedes, the development of T2D. Therefore, “If vitamin D supplementation can improve inflammation, as shown here, there may be important benefits for patients with T2D, given that elevated [inflammatory] markers promote insulin resistance, dyslipidaemia, and atherosclerosis,” explained Associate Professor de Courten.
“This meta-analysis suggests that vitamin D supplementation may be a beneficial adjunct therapy to reduce subclinical inflammation in patients with type 2 diabetes, potentially preventing or delaying disease progression. However, more research needs to be done in this area.” she added.
The review suggests further large RCTs are needed to confirm the effects of vitamin D on inflammatory markers. These trials need to assess clinical endpoints and long-term effects to determine whether the reduced inflammation translates into improved health outcomes in T2D patients, the researchers emphasised.
“At this stage, vitamin D supplementation can’t be recommended for primary or secondary prevention for diabetes on a population basis. However, there may be a benefit for certain subpopulations of people (i.e. certain ethnic groups or patients with pronounced inflammation),” said de Courten
“Until we can confirm positive effects of vitamin D supplementation on cardiometabolic health in specific populations, the best strategy is having enough vitamin D through diet and exposure to sunshine while considering current recommendations for skin cancer prevention,” she concluded.
Source: Nutrition Reviews
Volume 76, issue 5, pp 380-394, doi: 10.1093/nutrit/nux077
“Vitamin D supplementation for improvement of chronic low-grade inflammation in patients with type 2 diabetes: a systematic review and meta-analysis of randomized controlled trials”
Authors: Aya Mousa, Negar Naderpoor, Helena Teede, Robert Scragg, Barbora de Courten