This clinical study, designed as a double-blind, randomized, placebo-controlled trial, aims to investigate the potential of nicotinamide riboside (NR) to decelerate functional decline in the elderly frail population. In animal studies, NR, which is converted to nicotinamide adenine dinucleotide (NAD), has shown potential as a neuroprotective agent, with indications of protection against amyotrophic lateral sclerosis (ALS), Alzheimer's dementia, and Parkinson's disease. Furthermore, aging is commonly associated with decreased tissue NAD levels, a phenomenon linked to premature aging and a spectrum of age-related disorders, including cardiovascular diseases and cancers. Existing preclinical and clinical research highlights the promise of NAD replenishment through enhanced DNA repair, sirtuin activity, and improved mitochondrial function. The research center has conducted two phase II clinical trials on NR for Parkinson's disease (NAD-PARK and NR-SAFE), administering up to 3000 mg of NR daily. These trials have shown promising results, indicating NR's potential as a treatment that may alter the course of the disease and possibly as neuroprotective treatment in Parkinson's disease. The NAD age trial primarily aims to determine: * The efficacy of NAD therapy in improving clinical symptoms of frailty, evaluated through standardized physical and cognitive function tests. * The safety of administering 2000 mg NR daily in an elderly frail population. The study will include 100 individuals, classified as frail based on the Fried Frailty Phenotype. Participants will be randomly assigned to receive either 2000 mg of NR daily or a placebo. Over a 52-week period, participants will undergo: * Clinical evaluations, including actigraphy and questionnaires. * Cognitive assessments. * Bio sampling. * Magnetic resonance imaging (MRI). * Positron emission tomography (FDG-PET) scanning. The outcomes of this study could potentially demonstrate that NR effectively reduces signs of frailty, offering considerable advantages to the individuals affected, their families, and society as a whole.