Supplement interactions
Every rule in our dataset, with mechanism, practical advice and an honest evidence rating.
Conflicts — take apart or watch the dose
ConflictCopper + ZincHigh-dose zinc can cause copper deficiencyConflictCalcium + IronCalcium reduces iron absorption from the same mealConflictIron + ZincZinc and iron compete when taken together without foodNoteCurcumin + IronCurcumin binds ironConflictCaffeine + IronCoffee and tea reduce iron absorptionConflictGreen Tea Extract + IronGreen tea catechins block iron absorption
Cautions
NoteCalcium + MagnesiumVery high calcium may reduce magnesium absorptionNoteMagnesium + ZincVery high zinc can reduce magnesium absorptionNoteCalcium + ZincCalcium may modestly lower zinc absorptionNoteAshwagandha + L-TheanineAdditive calming effectsNoteVitamin A + Vitamin D3High-dose vitamin A may blunt vitamin DNoteCaffeine + Green Tea ExtractHidden caffeine adds upNoteCaffeine + CreatineCaffeine may blunt creatine's benefits — or notNoteIron + Psyllium HuskFiber can reduce iron absorptionNoteCalcium + Psyllium HuskFiber can reduce calcium absorptionNotePsyllium Husk + ZincFiber can reduce zinc absorptionNoteMagnesium + Psyllium HuskFiber can reduce magnesium absorptionNoteVitamin B Complex + Vitamin B6Double-counting B6NoteVitamin E + Vitamin K2High-dose vitamin E antagonizes vitamin KNoteBerberine + ChromiumAdditive blood-sugar loweringNoteAlpha-Lipoic Acid + BiotinLipoic acid shares biotin's transporterNoteNMN + Nicotinamide Riboside (NR)Two NAD⁺ precursors are redundantCritical5-HTP + St. John's WortSerotonin syndrome riskNoteGinkgo + Vitamin ETwo supplements that affect bleeding
Synergies — work well together
SynergyIron + Vitamin CVitamin C boosts non-heme iron absorptionSynergyVitamin D3 + Vitamin K2D3 makes calcium-binding proteins; K2 activates themSynergyMagnesium + Vitamin D3Magnesium is required to activate vitamin DSynergyCalcium + Vitamin D3Vitamin D increases calcium absorptionSynergyCalcium + Vitamin K2K2 helps direct calcium into boneSynergyCurcumin + PiperinePiperine increases curcumin bioavailabilitySynergyPiperine + ResveratrolPiperine may increase resveratrol exposureSynergyOmega-3 (Fish Oil) + Vitamin D3Dietary fat improves vitamin D3 absorptionSynergyOmega-3 (Fish Oil) + Vitamin K2Fat-soluble K2 absorbs better with fatSynergyOmega-3 (Fish Oil) + Vitamin AFat-soluble vitamin A absorbs better with fatSynergyCoQ10 + Omega-3 (Fish Oil)CoQ10 absorbs better with fatSynergyNMN + ResveratrolThe NAD⁺ + sirtuin hypothesisSynergyCaffeine + L-TheanineL-theanine smooths caffeine's edgeSynergyFolate + Vitamin B12Folate and B12 work as a pairSynergyVitamin C + Vitamin EVitamin C recycles vitamin ESynergyOmega-3 (Fish Oil) + Vitamin EVitamin E protects omega-3s from oxidationSynergyAstaxanthin + Omega-3 (Fish Oil)Fat-soluble astaxanthin absorbs with fish oilSynergySelenium + Vitamin EComplementary antioxidant systemsSynergyIodine + SeleniumBoth are needed for thyroid hormoneSynergyMagnesium + PotassiumLow magnesium makes low potassium hard to fixSynergyCollagen Peptides + Vitamin CVitamin C is needed to build collagenSynergyAcetyl-L-Carnitine + Alpha-Lipoic AcidThe classic mitochondrial pairingSynergyNicotinamide Riboside (NR) + ResveratrolThe NAD⁺ + sirtuin hypothesis (NR version)