Ageing is associated with cognitive decline, which is a significant factor in the development of dementia. Vitamin B12 (VB12) is crucial for maintaining proper nervous system function, as well as for protein, fat, and carbohydrate metabolism, and DNA synthesis. Moreover, it helps prevent serious health conditions such as pernicious anemia, neurodegenerative diseases, and Alzheimer's disease. VB12 deficiency is common among the elderly population. We found that serum VB12 levels were significantly elevated in centenarians. Interestingly, VB12 supplementation delayed aging but also improved learning and memory in nematodes. Our results suggest that increasing VB12 activates ptp-3 and helps maintain good cognitive function in centenarians. Furthermore, aging is the gradual decline in bodily functions that impacts nearly all living organisms, with significant effects on salivary glands. Salivary gland degeneration may contribute to VB12 deficiency in the elderly, underscoring the crucial role of salivary regulation in VB12 absorption for centenarians.