1. The most important factor is your existing iron level. A low iron level will increase absorption, while a high iron level will decrease absorption. In general, you absorb 10-15% of the iron from foods.2
2. Meat proteins will increase the absorption of nonheme iron.2
3. Vitamin C will increase the absorption of nonheme iron by as much as 85%.2,3
4. Tannins, oxalates, polyphenols, and phytates found in tea and coffee can reduce the absorption of non-heme iron by up to 65%. Black tea reduces absorption more than green tea and coffee.2,3,4
5. The following teas and beverages also inhibit iron absorption: Peppermint tea, cocoa, vervain, lime flower, chamomile, and most other herbal teas with polyphenols.4
6.Calcium, polyphenols, and phytates found in legumes, whole grains, and chocolate can reduce absorption of nonheme iron.
7. Some protein from soy products may inhibit nonheme iron absorption.2
8. Calcium, milk, and antacids can inhibit absorption of iron supplements.5
9. High fiber foods, such as whole grains, raw vegetables, and bran can inhibit absorption of iron supplements.5
10. Foods or drinks with caffeine can inhibit absorption of iron supplements.5
Source:
https://www.healthaliciousness.com/articles/food-sources-of-iron.php
