Interaction fact sheet
Zinc and iron
Monitor: genuine competition, especially on an empty stomach and at high doses.
Iron and zinc share some absorption pathways. When taken together on an empty stomach, high-dose iron reduces zinc absorption. When taken with a meal, the effect is no longer observed.
In brief
- Mechanism
- Iron and zinc compete for some of the transporters in the intestine.
- Magnitude
- Measurable effect mainly above around 25 mg of iron, in solution or on an empty stomach.
- Who is affected
- People taking high-dose iron for a deficiency alongside a zinc supplement.
- What to do
- Take zinc at a different time from iron, or with a meal.
What the studies say
A review published in 1998 brings together studies in humans. Several showed that a high iron concentration reduces zinc absorption in adults when both are given in solution on an empty stomach. When taken with a meal, the effect is no longer seen. Iron fortification of foods at usual doses does not interfere with zinc absorption.
A threshold of around 25 mg of iron has been proposed for an effect to become measurable: this is the dose found in supplements prescribed for a deficiency.
In practice
What you can do
- If you take iron for a deficiency, take your zinc at a different time of day.
- A multivitamin containing both at low doses, taken with a meal, poses no notable problem.
- Avoid long-term high doses of zinc, which deplete copper.
When to seek advice
- Confirmed iron deficiency: decide on treatment and its timing with your doctor.
- Persistent fatigue despite supplementation.
Main sources
- 01Whittaker P. Iron and zinc interactions in humans. American Journal of Clinical Nutrition, 1998. PubMed
Frequently Asked Questions (FAQ)
Can you take zinc and iron at the same time?
At low doses and with a meal, yes. With high-dose iron taken on an empty stomach, it's better to take zinc a few hours apart.
Does zinc interfere with iron?
A high dose of zinc can also slightly reduce iron absorption. Taking them at different times solves both problems.