Every cell makes its energy (ATP) by running glucose and fat through the mitochondria — and almost every step needs a vitamin cofactor. The B-complex (B1, B2, B3, B5) are the literal hand-off molecules of the Krebs cycle and electron transport chain; iron sits inside the cytochromes that shuttle electrons; magnesium stabilizes the ATP molecule itself; B12 keeps the whole system supplied with usable substrate. When these cofactors run low the machinery still turns, just slowly — felt as the kind of fatigue that doesn't improve with rest. This is the supply chain sitting underneath every other system on this list. These 48 whole foods are ranked by how many of the key energy nutrients a typical serving delivers (≥10% DV each).