Low Levels of Vitamin B6 and B12 Linked to Patients’ Nerve Damage

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by Marisa Wexler |

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Neuropathy, or nerve damage, was linked to abnormally low levels of the vitamins B6 and B12 in three people with Parkinson’s disease, according to a case report.

“All patients were consecutively identified within one year at a single institution,” the researchers wrote, which suggests that neuropathy associated with low levels of these vitamins “may be an unrecognized entity.” As such, the team stressed the importance of measuring levels of vitamins B6 and B12 when neuropathy is suspected.

“Monitoring B6 and B12 levels even if neuropathy symptoms are not present should also be considered,” the researchers added. “Timely recognition and treatment of both vitamin deficiencies could lead to improved outcomes in these patients.”

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The report, “Neuropathy due to coexistent vitamin B12 and B6 deficiencies in patients with Parkinson’s disease: A case series,” was published as a letter to the editor in the Journal of the Neurological Sciences.

Vitamin B6 and vitamin B12 are essential nutrients for the body. Of particular note, these vitamins are involved in some of the molecular processes used to make the signaling molecule dopamine.

Parkinson’s is caused by the death and dysfunction of dopamine-producing cells in the brain, and standard its treatment (levodopa and its derivatives) essentially involves giving the brain more raw materials with which to manufacture dopamine.

The researchers noted that high daily doses of levodopa or similar medications may lead to an increased need for vitamins B6 and B12 to help in making dopamine, as these molecules share some metabolic pathways that require a certain balance.

A team at the University of Rochester in New York described three Parkinson’s patients on relatively high doses of levodopa (one gram or more) who developed neuropathy: a 53-year-old man, a 75-year-old woman, and a 59-year-old woman.

After some time on levodopa treatment (between three and 10 years), all three patients developed symptoms indicative of neuropathy, such as numbness, tingling, or pain in the extremities.

In the first two, initial testing revealed low levels of vitamin B12, so supplements of this nutrient were given. But symptoms persisted in both patients, and further testing revealed unusually low levels of B6 as well.

Adding B6 supplements, along with those for B12, eased their neuropathy symptoms.

According to the researchers, these cases highlight that “B12 supplementation may unmask B6 deficiency” in people with Parkinson’s, since both vitamins are consumed in the process of making dopamine.

The third patient was found to have low B6 levels with initial testing, and her symptoms also eased with B6 and B12 supplements.

“Current neuropathy workup guidelines recommend screening for folate [folic acid, a type of vitamin B] and B12 deficiencies, but not for B6 deficiency,” the researchers wrote.

“Since coexistent deficiencies may be more frequent in PD [Parkinson’s disease], we propose that B6 levels should also be checked in this population when there is concern for neuropathy,” they concluded.

The team also stressed the importance of measuring levels of B6, B12, and related molecules during and after treatment for all Parkinson’s patients.

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