The collated evidence notes associations between deficiencies and adversities such as impaired mental health status, metabolic syndrome, risk of obesity, heightened blood pressure, and dyslipidaemia.
The Malaysian researchers emphasise: “Based on our best knowledge, this is the first review to discuss the impact of vitamin D deficiency and insufficiency on outcomes of T2DM patients.”
“Due to the diverse implications of vitamin D deficiency, screening for vitamin D levels in T2DM patients may be beneficial,” they add, highlighting the potential benefits for dietary interventions within such patients.
The importance of vitamin D has been a highly discussed topic over recent years, with studies highlighting the benefits that have been associated with an optimal status, from immunity to bone health. However, vitamin D deficiencies are vastly prevalent as a result of malnutrition within low- and middle- income countries, as well as inadequate exposure to ultraviolet B (UBV) radiation due to geographical and cultural differences.
Specifically, recent studies have highlighted the potential link between vitamin D deficiencies and metabolic syndrome, such as T2D; a condition found to be one of the most prevalent non-communicable diseases globally. Associations have been found between such deficiencies and decreased insulin resistance and release, suggesting its involvement in glycaemic control and the potential progression of diabetes.
In the face of controversies in this area and a general lack of evidence, the researchers sought to conduct a review gathering the available evidence on the impact of vitamin D deficiencies on the development and outcomes of T2D patients.
The researchers utilised the scientific database of Web of Science, Scopus, and PubMed to collate data published between 2012 and 2022, resulting in the inclusion of 33 eligible studies.
The collated results established significant associations between vitamin D deficiencies or insufficiencies with adverse outcomes such as mental health status, metabolic syndrome, increased risk of obesity, increased blood pressure, dyslipidaemia, and poor glycaemic control, within T2D patients.
One included study established that such a deficiency was found to be as a clear risk factor for metabolic disease, with another noting that this may result from altered insulin secretion and sensitivity. Furthermore, vitamin D supplementation was able to improve lipid profile, hyperglycaemic and obesity in such patients. The effects on insulin production were noted in a further seven studies, which established a significant relationship between low vitamin D levels and HbA1c, highlighting the effects of deficiencies on glycaemic control.
Further data established a link between obesity in deficient diabetics, due to this decreased insulin production activating the lipogenesis mechanism which ultimately increases fat mass.
With regards to the detailed inverse relationship between vitamin D deficiencies and increased blood pressure, the report explained the effect resulted from the vitamin’s key regulatory effect of the renin-angiotensin system (RAS), which plays a critical role in blood pressure maintenance.
“In conclusion, vitamin D deficiency and insufficiency have multiple impacts on the outcome of T2DM patients,” the report states, an effect explained by the array of functions vitamin D is involved with throughout the body.
In light of the findings highlighting the cascade of detrimental health outcomes, the researchers highlight the potential need for vitamin screening to be implemented within diagnosed diabetic patients.
"The Impact of Vitamin D Deficiency and Insufficiency on the Outcome of Type 2 Diabetes Mellitus Patients: A Systematic Review"
by Zaleha Md Isa, Norizzati Amsah and Norfazilah Ahmad