Polyamines have been of interest since spermadine was shown to extend life in mice. Another topic of growing interest is the influence of gut bacteria on metabolism and longevity, and here is research to link these two items: "In mammals, levels of polyamines (PAs) decrease during the ageing process; PAs are known to decrease systemic inflammation by inhibiting inflammatory cytokine synthesis in macrophages. ... The probiotic strain Bifidobacterium animalis subsp. lactis LKM512 is known to increase intestinal luminal PA concentrations. ... We supplemented the diet of 10-month-old Crj:CD-1 female mice with LKM512 for 11 months, while the controls received no supplementation. Survival rates were compared [and] LKM512-treated mice survived significantly longer than controls; moreover, skin ulcers and tumors were more common in the control mice." A caution here is that this result may well involve inadvertent calorie restriction: any dietary supplementation may affect appetite and thus level of caloric intake, and all studies have to be considered in light of the fact that even mild calorie restriction has beneficial effects on mouse health and life span.