*This is a summary of the findings from various studies and articles. Further information and details on this study are located in the links below.*
Spermidine is a natural polyamine present in all living organisms that is critically involved in the maintenance of cellular homeostasis. In general, polyamine levels in individual organisms are highly diverse. Nevertheless, one commonality is that tissue concentrations of spermidine decline in an age-dependent manner in both model organisms and humans.
Intriguingly, external supplementation of spermidine exerts various beneficial effects on aging and age-related diseases. For example, spermidine feeding extends lifespan across species, promotes cardio- and neuroprotection, stimulates antineoplastic immune response and may avoid immunosenescence by stimulating memory T-cell formation. Many of these anti-aging properties have been causally linked to the capacity of spermidine to ensure proteostasis through the stimulation of cytoprotective macroautophagy. Age-associated conditions including cancer, neurodegeneration and cardiovascular diseases are directly connected to the intracellular accumulation of toxic debris, and its removal by autophagy constitutes a well-documented avenue for protection against age and disease. Furthermore, spermidine exhibits anti-inflammatory and antioxidant properties, enhances mitochondrial metabolic function and respiration, promotes chaperone activity and improves proteostasis.
In sum, in our view, spermidine is synthesized by our organism in sufficient quantities during youth, but not in old age. Thus, one may argue that, as we age, spermidine evolves to the status of a vitamin, and thus has to be supplemented from external sources to secure the maintenance of autophagic flux required for organismal homeostasis.
Frank Madeo, Maria A Bauer, Didac Carmona -Gutierrez, et al. Spermidine: a physiological autophagy inducer acting as an anti-aging vitamin in humans?, online: https://www.tandfonline.com/doi/full/10.1080/15548627.2018.1530929