Which of the following decreases iron absorption when consumed with iron supplements?

• A. Dairy/Calcium
• B. Vitamin C
• C. Citrus fruits
• D. Meat

Answer: (A)

Iron absorption can be affected by other nutrients in the same meal. Calcium from dairy products can reduce how much iron the body takes up when iron supplements are consumed together with it. The likely reason is that calcium competes with iron for absorption in the intestinal lining or forms less soluble complexes, lowering the amount of iron that enters the bloodstream. This effect is especially noted with non-heme iron, which is what most supplements contain.

In contrast, foods rich in vitamin C, like citrus fruits, help iron absorption by lowering the gut pH and keeping iron in the soluble ferrous form, making it easier to absorb. Meat contains factors that can further enhance absorption of non-heme iron when eaten with iron sources.

So, the best choice reflects the idea that dairy/calcium-containing foods decrease iron absorption when taken with iron supplements. To optimize absorption, stagger calcium-containing foods or supplements away from iron supplements by a few hours, and consider pairing iron with vitamin C-rich foods if appropriate.