TCN2 and gastroesophageal reflux disease: Elderly persons are more likely to take medications such as proton pump inhibitors (PPIs) for heartburn, which are associated with vitamin B12 deficiency, and elderly persons with a generic variant in the transcobalamin gene TCN2 (C776G) who consume twice the recommended daily allowance (RDA) of folate are seven times more likely to have neuropathy [36].