Gut microbiota is changing constantly from birth to death, and in a similar way for most of the population. Common lifestyle habits of elderly people affect how it changes, and the new composition of microbiota in old age contributes to greater systemic inflammation, which accelerates the aging process andage-associated diseases. This paper examines the evidence available to this day on gut microbiota changes in old people and centenarians. It then considers the differences between both groups, with the aim of understanding why centenarians live longer. Finally, based on the information obtained, some of the products currently available on the market are examined to determine if they could be prescribed to improve the health of elderly people, and an ideal probiotic product for healthy aging is proposed.