This is work performed on cells rather than organisms, but it still might be added to the great weight of existing evidence to suggest that calorie restriction improves most aspects of health: "Heart cells starved of nutrients are less likely to be damaged during periods of decreased blood flow and sudden influxes of blood, known as ischemia and reperfusion, and are also less likely to get out of synch with their cellular neighbors, the damaging phenomenon called arrhythmia. ... scientists learned that starved heart cells maintain normal calcium cycling and basic mitochondrial function far longer than non-starved cells during periods of extreme stress. The findings [add] to a growing body of scientific evidence that suggests the consumption of less energy - while maintaining balanced nutrition - can benefit tissues by enhancing cell performance and reducing DNA damage associated with the aging process. ... We are connecting several loose facts about calorie restriction and heart function, in particular, arrhythmias. We have shown why nutrient restriction protects the cells from ischemia and reperfusion. Normal function means less risk of arrhythmias, during which heart cells stop communicating properly with each other, and which can cause further damage, even sudden cardiac death. ... The scientists studied cultured heart cells originally derived from young rats. The cells were grown in a 2 cm-by-2 cm monolayer, to allow ease of study. The researchers mapped intracellular calcium ions and mitochondrial membrane potential with the help of fluorescent tags. Ischemia was simulated by placing a 1.8 cm-by-1.8 cm cover slip over the center of the cell culture, which limited oxygen and nutrient flow to that portion of the culture. Reperfusion was simulated by the removal of the cover slip. ... These experiments are not yet telling us whether we can emulate the effects of nutrient restriction in humans to lessen the damage of ischemia-reperfusion. But we have shown one way nutrient restriction may be acting to reduce heart tissue damage, a subject of interest to many laboratories."