Popular anti-aging supplements could be inadvertently helping one of medicine's most aggressive cancers resist treatment. This discovery challenges the widespread assumption that boosting cellular energy metabolism is universally beneficial, particularly for cancer patients seeking complementary therapies during chemotherapy. The research examined three commercially available NAD+ precursors—nicotinamide (NAM), nicotinamide riboside (NR), and nicotinamide mononucleotide (NMN)—against pancreatic ductal adenocarcinoma, a cancer with notoriously poor survival rates. NMN demonstrated the most pronounced protective effects, significantly reducing the efficacy of standard chemotherapy drugs including oxaliplatin, 5-fluorouracil, and gemcitabine. The supplements enhanced cancer cell survival by strengthening mitochondrial function, reducing oxidative stress, and preventing DNA damage—the very mechanisms through which chemotherapy typically kills cancer cells. Both laboratory cultures and live mouse models confirmed these resistance patterns, with tumors growing more aggressively when animals received NAD+ supplementation alongside chemotherapy. The implications extend beyond pancreatic cancer research into broader longevity supplement use. While NAD+ boosters show promise for healthy aging by supporting cellular energy production and DNA repair, these same protective mechanisms may shield cancer cells from therapeutic damage. This creates a clinical paradox: supplements designed to promote cellular health could potentially compromise cancer treatment outcomes. The findings suggest cancer patients should exercise extreme caution with NAD+ precursors during active treatment, though the research doesn't address whether timing supplementation around chemotherapy cycles might mitigate these effects.