You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Ageing and gut microbes: perspectives for health maintenance and longevity. The ageing process affects the human gut microbiota phylogenetic composition and its interaction with the immune system. Age-related gut microbiota modifications are associated with immunosenescence and inflamm-ageing in a sort of self-sustaining loop, which allows the placement of gut microbiota unbalances among both the causes and the effects of the inflamm-ageing process. Even if, up to now, the link between gut microbiota and the ageing process is only partially understood, the gut ecosystem shows the potential to become a promising target for strategies able to contribute to the health status of older people. In this context, the consumption of pro/prebiotics may be useful in both prevention and treatment of age-related pathophysiological conditions, such as recovery and promotion of immune functions, i.e. adjuvant effect for influenza vaccine, and prevention and/or alleviation of common "winter diseases", as well as constipation and Clostridium difficile-associated diarrhoea. Moreover, being involved in different mechanisms which concur in counteracting inflammation, such as down-regulation of inflammation-associated genes and improvement of colonic mucosa conditions, probiotics have the potentiality to be involved in the promotion of longevity.
{"Chemical": []}