What substances are known to decrease the absorption of iron?

The substances known to decrease the absorption of iron include coffee, phytates, and tannins.

Coffee contains polyphenols, particularly tannins, which can bind to iron and hinder its absorption in the intestines. Phytates, found in whole grains, legumes, and certain seeds, are known to inhibit iron absorption by forming insoluble complexes with iron, rendering it less available for uptake. Tannins are also present in a range of beverages, particularly tea and red wine, and similarly interfere with iron's bioavailability due to their binding properties.

Understanding these interactions is essential for managing dietary intake, especially for individuals at risk of iron deficiency, like vegetarians, pregnant women, or those with certain medical conditions. Adjusting the timing of consumption of these substances relative to iron-rich meals can help improve iron absorption. The other choices do not have the same inhibitory effects on iron absorption and may not be relevant in this context. For instance, while vitamin C can actually enhance iron absorption, calcium and protein do not specifically inhibit it in a significant manner compared to the substances mentioned in the correct answer.