What Supplements Should Not Be Taken Together?
Quick Answer
Main conflicts: calcium blocks iron, zinc, and magnesium absorption. Iron blocks zinc. High-dose vitamin E interferes with vitamin K. Fiber blocks mineral absorption. Space these 2-4 hours apart. Most other combinations are fine.
Key Points
- Calcium is the biggest blocker. Take it separately.
- Iron and zinc compete. Take at different meals.
- Fiber binds minerals. Take minerals 2+ hours from fiber supplements.
- Coffee/tea with iron is a bad combo.
- Most supplements are fine together.
Detailed Answer
REAL CONFLICTS (Space 2-4 hours apart):
• Calcium + Iron: Calcium reduces iron absorption by 50%+ • Calcium + Zinc: Compete for same absorption pathways • Calcium + Magnesium: High doses compete (normal doses okay) • Iron + Zinc: Compete for absorption at high doses • Fiber + Minerals: Fiber can bind minerals, reducing absorption
MINOR CONCERNS (Usually fine, but optimal to separate):
• Coffee/Tea + Iron: Tannins reduce iron absorption 60%+ • Vitamin E + Vitamin K: High-dose E may interfere with K • Zinc + Copper: High zinc depletes copper over time
COMMON MYTHS (Actually fine together):
• Calcium + Vitamin D: Take together. D helps calcium absorption • Magnesium + Vitamin D: Take together. Magnesium helps D activation • Fish oil + Most things: Generally compatible • B vitamins + Most things: Water-soluble, few interactions
PRACTICAL APPROACH: Take calcium separately from everything else. Take iron separately from minerals. Most other combinations are fine.
Evidence Quality
Multiple high-quality studies support this
Key Sources:
- reviewMineral-Mineral Interactions in Human Nutrition
- studyCalcium and Iron Absorption: Timing Strategies
Related Questions
Multivitamins have low enough doses that interactions are minimal. The real issues are with high-dose individual supplements.
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