Which of the following may interfere with the absorption of iron?

Antacids, milk, and tetracycline can indeed interfere with the absorption of iron. Each of these substances has distinct properties that impact iron bioavailability.

Antacids contain compounds like magnesium or calcium, which can bind to iron in the gastrointestinal tract, thereby preventing it from being absorbed into the bloodstream. The presence of these minerals can form insoluble complexes with iron, diminishing its systemic availability.

Milk contains calcium, which can also attach to iron and create a complex that the body cannot absorb effectively. This is particularly significant in cases of iron deficiency, as consuming iron supplements with milk may reduce the intended therapeutic effect.

Tetracycline, an antibiotic, can chelate iron as well, meaning it has the ability to bind to iron and form a stable complex that the body cannot utilize. This is crucial because when taken together, tetracycline and iron supplements can essentially negate each other's absorption, leading to ineffective treatment outcomes.

The other options, such as vitamin C and citrus fruits, actually enhance iron absorption by reducing iron to a more soluble form and promoting its uptake. Fiber-rich foods, while generally beneficial for the digestive system, do not have the same impact on iron absorption as those substances listed in the correct option.