Recent aging studies have shown that caloric restriction and fasting have a prolonging effect on lifespan. A compelling new study by a team of Japanese researchers has offered an incredibly thorough examination into the metabolic alterations that occur in human blood during fasting, revealing a fascinating array of changes that could point to a variety of health benefits.
The research set out to exhaustively analyze the metabolic profile of blood samples as subjects underwent an extensive stretch of fasting. Four healthy participants were recruited and subjected to a long fast, with blood samples taken at three points in the process: 10, 34 and 58 hours after commencing fasting.
The researchers identified 44 different blood-based metabolites significantly increasing in abundance after 58 hours of fasting. Alongside known markers signaling the body is moving to utilizing alternative energy stores, such as butyrates and branched-chain amino acids, an interesting increase in anti-oxidant metabolites was found suggesting that the response could be an evolutionary defense against the oxidative stress put on the body during fasting.
Other previously unidentified metabolites revealed in the study signaled enhanced mitochondrial activity. This discovery adds weight to a compelling Harvard study from last year that suggested that fasting could increase longevity and promote healthy aging by kickstarting youthful plasticity in mitochondrial networks.
Interestingly, three specific metabolites known to be associated with aging and longevity – leucine, isoleucine, and ophthalmic acid – all increased in levels after fasting. Prior study has revealed these specific metabolites essential for maintenance of muscle and antioxidant activity decrease with age and are found in notably low levels in the elderly. This result suggests the possibility of a rejuvenating effect by fasting.
One of the biggest limitations in this particular study was the small sample size. Although the ultimate increases in metabolites were consistent across all four subjects, how quickly those metabolites peaked did vary from person to person. The researchers note that further work in more subjects will hopefully resolve any questions over individual metabolic respond patterns.
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Teruya T. et al., Diverse metabolic reactions activated during 58-hr fasting are revealed by non-targeted metabolomic analysis of human blood
Scientific Reports, volume 9, Article Number: 854 (2019)https://www.nature.com/articles/s41598-018-36674-9#Sec10