Can Vitamin B12 improve nerve function in patients with diabetes and nerve dysfunction?

This study looked at the effectiveness of vitamin B12 in people with type 2 diabetes (T2D) and loss of nerve function. It found that the vitamin improved pain, sensation, and quality of life in these patients.

T2D is a condition that involves high levels of glucose (sugar) in the blood. Over time, high blood sugar can damage the nerves. This damage, known as diabetic neuropathy (DN), can include pain or numbness in the hands or feet. It can also include cardiac autonomic neuropathy (CAN), which impacts the nerves controlling the heart. CAN increases the risk of heart attack and can cause slow or irregular heartbeats.

In addition to medications and diet for controlling blood sugar, a vitamin B12 supplement is sometimes used for patients with DN. The body needs vitamin B12 to make DNA (genetic material), and it is used by the nerves and blood cells. It can be found in meat, fish, and dairy. People with T2D are more likely to have a low level of this vitamin, particularly if they use the medication metformin (Glucophage). A lack of vitamin B12 can contribute to nerve damage. It is not clear whether vitamin B12 supplements can improve DN.

This study included 90 patients with T2D who had DN. All of the patients were using metformin in addition to other diabetes medications. Also, they all had good blood sugar control (HbA1c below 7.5%). Half of the patients were assigned to dissolve a vitamin B12 pill (methylcobalamin 1000 mcg) under their tongue each day. The other patients used a placebo (inactive pill). The patients were followed for one year.

The vitamin B12 levels in the blood improved significantly for the patients in the supplement group (232.0 to 776.7 pmol/L). There was no change in glucose control.

The researchers tested how well signals travel down the nerves by attaching a pair of electrodes to the skin. The nerve speed improved significantly for patients taking vitamin B12, compared to those taking placebo. The ability to feel a light vibration also improved in the B12 group. Additionally, they reported less pain and better quality of life than patients taking placebo.

Patients also underwent tests of the nerves controlling their body’s automatic functions. This includes how well the blood pressure adjusts to standing up, or to a breathing exercise known as the Valsalva maneuver. There was no change in automatic nerve function after taking vitamin B12. This suggests that vitamin B12 does not reduce the risk of heart attack for these patients.

There were no side effects from vitamin B12.

This study found that vitamin B12 improves nerve function and reduces pain for patients with T2D and DN who are taking metformin.

This study had a small number of participants at a single medical center. All participants were Caucasian. Therefore, the results may not represent all populations.

Ask your doctor whether a vitamin B12 supplement would be beneficial for you.