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Can Vitamin D Deficiency Cause Neuropathy?

May 7, 2011 | By Beth Greenwood
Can Vitamin D Deficiency Cause Neuropathy?
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Vitamin D, sometimes called the "sunshine vitamin" because the body synthesizes it from sunlight, affects a wide range of bodily functions, such as controlling calcium and phosphate levels, supporting bone growth and reducing inflammation. Neuropathy, a condition in which people experience tingling, burning and other kinds of pain without having been injured, is a complication of diabetes. There is a connection between the two, which researchers are beginning to understand.

About Vitamin D

Vitamin D can be found in some foods, such as oily fish and egg yolks, and can also be manufactured by the human body through exposure to ultraviolet rays in sunlight. The National Institutes of Health notes that while deficiencies are rare in the United States due to adequate food sources and sun exposure, there are some regions, particularly in the winter in northern cities, where sun exposure may be limited. People who rarely go outdoors may not meet their bodies' vitamin D requirements, while those over the age of 70 tend to have higher vitamin D requirements and may need supplementation. Vitamin D deficiency can cause rickets, a bone disorder in children that leads to softening of the bones and deformities. Rickets is easily prevented or corrected by ensuring adequate intake of calcium, phosphorus and vitamin D, although if treatment is not begun until the child's bones are well-developed deformities may remain. In adults, lack of vitamin D can cause osteomalacia, or softening of the bones, with consequent risk of fracture.

Diabetic Neuropathy

Diabetic neuropathy is one of the complications that tends to develop over time, especially if the diabetic's blood sugar is not kept under control. Damage to nerve tissue can be temporary or permanent and affects peripheral nerves as well as those that regulate vital functions such as heart muscle or digestion. According to PubMed Health, a National Center for Biotechnology Information website, approximately half of diabetic patients will develop neuropathy, and symptoms usually begin between 10 and 20 years after diagnosis. Described as tingling, burning or itching pain, diabetic neuropathy is difficult to manage because the medications that are available tend to be narcotics with a risk of addiction or other types of medications that have unfortunate side effects. The medications do not provide a cure but are used to manage the symptoms.

The Research

Limited research has been conducted on diabetic patients with neuropathy. A fairly high percentage of diabetics have been found to have low vitamin D levels, but there had been no investigation into the impact of vitamin D and its connection to neuropathy, Paul Lee and Roger Chen reported in the 2008 issue of "Archives of Internal Medicine." Because there is considerable debate about exactly what constitutes vitamin D deficiency, the researchers did not try to identify an actual deficiency but simply measured the vitamin D levels of the study participants. Serum vitamin D levels below 12 ng/ml --- nanograms per milliliter --- are known to cause osteomalacia and resultant nerve pain. This condition responds to vitamin D supplementation. Participants who were classed as vitamin D insufficient --- serum 25D concentration below 24 ng/ml --- were treated with cholecalciferol, also known as vitamin D3. Patients reported significant reductions in pain scores --- in some cases as much as 48 percent --- after three months of treatment with cholecalciferol. The research team recommended a trial of vitamin D supplementation in diabetic patients with neuropathy and noted that raising the serum vitamin D levels to greater than 24 ng/ml would improve pain symptoms without side effects and improve function. While Chen and Lee did not find specific evidence that vitamin D deficiency causes neuropathy, the researchers said that a deficiency may be a contributory factor, possibly by making diabetic nerve damage worse. Insufficient vitamin D may also impair the receptors in the body that respond to pain signals.

Considerations and Warnings

Diabetic neuropathy is a complex condition that should not be self-managed. While Lee and Chen found no adverse effects from vitamin D supplementation in their trial, if you have neuropathy and are considering supplementation, discuss your situation with a health-care professional.

References

Article reviewed by Eric Lochridge Last updated on: May 7, 2011

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