In a new meta-analysis, researchers out of China have found that vitamin D deficiency may contribute to diabetic peripheral neuropathy.
Diabetic neuropathy is a group of nerve disorders caused by diabetes that affects 60-70% of people with diabetes. Diabetic peripheral neuropathy (DPN) is a type of diabetic neuropathy that occurs in the arms and legs, and can result in symptoms such as numbness, tingling, burning, sensitivity to touch, and loss of balance.
Researchers have yet to determine the cause of DPN. However, it is thought that oxidative stress from hyperglycemia and inflammation plays a role.
Studies looking specifically at vitamin D and DPN are scarce. Because vitamin D has been shown to help maintain beta cell function and reduce inflammation, some researchers speculate that low levels of vitamin D may be a risk factor for DPN.
In late 2014, a research team from China analyzed all available research on vitamin D and DPN to determine if vitamin D is related to risk of DPN in patients with diabetes.
They searched the available literature for studies that looked at vitamin D levels and DPN in type 2 diabetes or compared vitamin D levels in DPN patients to those without DPN.
Six observational studies equaling a total of 1,484 patients with type 2 diabetes were eventually included in the analysis.
Did a combined analysis of these studies reveal a relationship between vitamin D and DPN? Here’s what the researchers found:
- Compared to those without DPN, patients with DPN had a significantly lower average vitamin D level of 7.69 ng/ml (P < 0.001).
- After looking at the studies that adjusted for confounding variables, patients with a vitamin D level lower than 20 ng/ml had a 2.68 times increased risk for DPN compared to those with a higher level (P < 0.0001).
The researchers stated,
“In conclusion, this meta-analysis suggests that vitamin D is involved in the development of DPN in type 2 diabetic patients, and vitamin D deficiency is very likely to be associated with increased risk of DPN.”
They went on to add,
“The identification of the associations of DPN with modifiable risk factors can provide us some implications for the development of new therapies for DPN. Since vitamin D deficiency is a modifiable risk factor for DPN, vitamin D supplements may be an effective treatment for type 2 diabetics with DPN and vitamin D deficiency.”
The researchers note that the small number of studies and study population may limit their results.
They also acknowledge that the inclusion of cross-sectional and case-control studies limits their analysis, whereas the inclusion of prospective studies could improve understanding of vitamin D’s role in DPN. There are currently no published trials looking at vitamin D supplementation and DPN.
While systematic reviews and meta-analyses come with a few notable flaws, such as study differences, this research provides a comprehensive first-look at vitamin D’s role in DPN. Prospective studies should be conducted next, and followed by clinical trials, before firm conclusions can be made.