Mitochondria are the organelles that produce ATP via oxidative phosphorylation. They also generate ROS, regulate apoptosis, and signal cellular state.

Mechanism: Each cell has hundreds to thousands of mitochondria. Their density, function, and turnover all decline with age. Damaged mitochondria leak ROS, drive inflammation, and trigger senescence.

Use case: Improve quantity (mitochondrial biogenesis via Zone 2 training, fasting, cold exposure, PQQ) and quality (mitophagy via fasting, exercise, urolithin A, rapamycin).

Caveats: Mitochondrial supplements (CoQ10, PQQ, NAD+ precursors) help on the margins but don't replace the fundamentals. Exercise, sleep, nutrition.