Supplement Interactions Guide

Introduction

Supplements are often treated as harmless “natural” additions to a diet. But natural does not mean safe. Compounds that affect neurotransmitters, hormones, blood clotting, or metabolism can interact dangerously with medications, other supplements, or even foods. Knowing these interactions is not optional — it is survival.

High-Risk Combinations

St. John’s Wort + SSRIs / birth control: St. John’s Wort is a potent CYP3A4 inducer. It reduces drug levels, making antidepressants and hormonal contraceptives ineffective. This interaction has caused unplanned pregnancies and psychiatric relapses.

Fish oil + warfarin: Both thin blood. Together, they increase bleeding risk. Not forbidden, but requires monitoring and dose adjustment.

Iron + calcium / coffee: Iron and calcium compete for absorption. Coffee and tea contain tannins that bind iron, dramatically reducing its bioavailability. Take iron with vitamin C — and take calcium at a different time.

Tyramine-rich foods + MAOIs: Not a supplement interaction per se, but relevant: fermented foods, aged cheeses, and red wine contain tyramine, which can trigger hypertensive crises on MAOIs. Some supplements (hordenine, phenylethylamine) compound the risk.

5-HTP + antidepressants: Both increase serotonin. Together they risk serotonin syndrome — a potentially fatal condition marked by agitation, hyperthermia, and seizures. Never combine without physician guidance.

The Golden Rule

If you are on any prescription medication, run your supplement stack past a pharmacist or physician. The supplement industry will not flag these for you — labels list warnings most consumers never read.