I've seen some interesting research that point to oxaloacetate as a potential longevity-enhancing natural supplement by increasing NAD. I believe Alpha-Ketoglutarate also shares some of these properties (maybe through a different mechanism?)
I was looking at supplementing Citrate via Potassium Citrate (over my low carb diet) and continuing to supplement Malate via Citrulline Malate. Does Citrate have any effect on healthspan / longevity? How about supplemental malate?