High doses of vitamin B6 may cause peripheral neuropathy, damage to the fibers of the peripheral nervous system, researchers from the Department of Immunology at the Royal Melbourne Institute of Technology have told The Conversation.

Vitamin B6 (also known as pyridoxine) is a group of six compounds with a similar chemical structure. This important nutrient is essential for normal body function, but the human body cannot produce it on its own, so B6 is obtained from food (animal products, nuts, potatoes, oatmeal) or from supplements.

Pyridoxine is inactive in food. To activate vitamin B6, the liver converts it into a compound called pyridoxal-5-phosphate (PLP). In this form, the vitamin helps the body perform more than 140 cellular functions, including protein synthesis and breakdown, red blood cell production, blood sugar regulation, and brain function assistance.

According to researchers, adults aged 19 to 50 need 1.3 milligrams of vitamin B6 per day. The recommended amount is lower for adolescents and children, and higher for people 51 and older (1.7 milligrams for men and 1.5 milligrams for women) and for breastfeeding and pregnant women (1.9 milligrams).

It is not recommended to exceed these doses, as the accumulation of vitamin B6 in the blood leads to a condition called peripheral neuropathy. This occurs when the sensory nerves, which are located outside the brain and spinal cord and transmit information to the central nervous system, are damaged and stop working. Peripheral neuropathy is accompanied by varying degrees of sensory disturbances, pain, muscle weakness, and atrophy.

Researchers noted that the most common symptoms of hypervitaminosis B6 are numbness and itching—although in some cases, patients may experience difficulty with balance or walking.