L-Carnitine treatment reduces severity of physical and mental fatigue and increases cognitive functions in centenarians.
While the results of this study seem pretty amazing, the bottom line is that L-carnitine is necessary for fatty acids to be shuttled into the mitochondria to be burned for energy. So, basically, all the researchers did was increase the ability of these patients to create ATP and energy for the cells.
In addition to supplementation with L-carnitine, exercise, higher phytonutrient diet, low stress and a hundred other interventions will positively effect this same pathway.