The Potential of Fasting and Caloric Restriction to Mitigate Radiation Damage-A Systematic Review

Abstract

Detrimental health effects from ionizing radiation to living organisms is one of the key concerns identified and addressed by Radiation Protection institutions, nationally and internationally on Earth and for human spaceflight. Thus, new methods for mitigating the adverse effects of ionizing radiation are urgently needed for terrestrial health and deep space exploration. Caloric restriction and (intermittent-) fasting have been reported to elicit a variety of immediate and long-term physiological effects. The rapidly growing body of evidence of research studies investigating the effects of caloric restriction and dietary fasting points toward a multitude of benefits affecting numerous physiological systems. Therefore, a systematic review was performed to evaluate the evidence of caloric restriction and dietary fasting on the physiological response to ionizing radiation in humans and animals. All experimental studies of humans, animals, and eukaryotic cell lines available in PubMed, Cochrane library, and specialized databases were searched comparing irradiation post-caloric restriction or fasting to a non-nutritionally restricted control group on a broad range of outcomes from molecular to clinical responses. The initial search yielded 2,653 records. The final analysis included 11 studies. Most studies investigated survival rate or cancer occurrence in animals. Included studies did not reveal any benefit from pre exposure caloric restriction, except when performed with post radiation caloric restriction. However, the effects of pre-exposure fasting suggest increased resilience to ionizing radiation.

Keywords: SIRTUIN; caloric restriction; deep space; fasting; irradation; radio-protection; radiology; space flight.

Figure 1

Flow diagram of search and screening methodology. The flow of search results numbers and author's eligibility screening assessment is represented here.

Figure 2

Effect sizes for caloric restriction. Outcomes are plotted with the Hedges' G calculated for each outcome extracted and bias corrected for sample size. Confidence intervals of 95% are represented by the error bars. Effect size values that are in the positive rightward direction indicate a beneficial effect in favor of the intervention group compared to the control group. M, Mice; H, Humans.

Figure 3

Effect sizes for fasting. Outcomes are plotted with the Hedges' G calculated for each outcome extracted and bias corrected for sample size. Confidence intervals of 95% are represented by the error bars. Effect size values that are in the positive rightward direction indicate a beneficial effect in favor of the intervention group compared to the control group. GP, Guinea pigs; M, mice. *per circumference. ** effect size multiplied by −1.

Figure 4

Radio-protective potential of dietary restrictions. (A) Caloric Restriction (CR) explained by the time and Tendency of the intervention. Flows represent the total number of outcomes with a certain potential for effectiveness. (B) Fasting explained by the regime (Intermittent, Continuous), Intervals and radio-protective effectiveness of the intervention. The middle column represents the duration of one interval in days. Flows represent the total number of outcomes given intervals and tendency, respectively. Tendencies indicate whether the CR or Fasting have radio-protective potential (Beneficial), potentially increase radio-sensitivity (Negative) or have no effect (Non-beneficial). “Unk.” represents an unknown tendency.