Question

Bioavailability of iron is enhanced by _______.

• A. Phytates
• B. Tannins
• C. Ascorbic acid
• D. Oxalates

Hint:

Consuming Vitamin C-rich foods (like citrus fruits) alongside iron-rich plant meals significantly improves the absorption of non-heme iron.
Avoid drinking tea (tannins) or eating high-phytate foods during iron-rich meals.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks to identify the dietary component that increases the absorption and biological availability of iron in the human digestive system.

Step 2: Key Concepts and Approach:
Dietary iron exists in two forms: heme iron (from meat) and non-heme iron (from plant sources).
The absorption of non-heme iron ($Fe^{3+}$) is relatively low but can be enhanced or inhibited by other compounds in the gut.

Step 3: Detailed Explanation:

• Action of Ascorbic Acid (Vitamin C):
Ascorbic acid enhances non-heme iron absorption through two distinct chemical processes:
1. Reduction: It reduces ferric iron ($Fe^{3+}$, which is insoluble in the neutral pH of the small intestine) to ferrous iron ($Fe^{2+}$, which is soluble and readily absorbed by the body's iron transporters).
2. Chelation: It forms a stable, soluble chelate with iron, preventing it from binding to inhibitors or precipitating out of solution.

• Action of Inhibitors:
* Phytates (in grains) and Oxalates (in green leafy vegetables like spinach) bind iron, forming insoluble complexes that the body cannot absorb.
* Tannins (in tea and coffee) also bind iron tightly, reducing its absorption.

Step 4: Final Answer:
Ascorbic acid is the dietary component that enhances iron bioavailability.