Which factor reduces mineral bioavailability from plant-based foods?

• A. Vitamin C
• B. Cooking with calcium-rich foods
• C. Phytates and oxalates
• D. Light exposure

Answer: (C)

This question tests how compounds in plant foods influence how much mineral the body can absorb. In plant-based foods, certain compounds bind minerals in the gut and form complexes that are not easily absorbed. Phytates (found in whole grains, seeds, legumes, and nuts) strongly bind minerals such as iron, zinc, and calcium, reducing their intestinal uptake. Oxalates (present in leafy greens like spinach and in some other plant foods) bind minerals like calcium and iron, further lowering absorption. Because of these binding effects, even when plant foods contain minerals, the actual amount that enters the bloodstream can be limited.

Vitamin C, by contrast, can enhance non-heme iron absorption when consumed with iron-rich plant foods, helping absorption rather than hindering it. Light exposure doesn’t influence mineral absorption, and while some interactions can occur with minerals during cooking, the binding effects of phytates and oxalates are the primary, well-documented factors that reduce mineral bioavailability in plant-based diets.