Final answer:
Phytates and oxalates limit the body's ability to absorb calcium by forming insoluble salts within the intestines. This impairs the bioavailability of calcium which is crucial for bone health and other physiological functions.
Step-by-step explanation:
Phytates and oxalates are known to interfere with the absorption of certain minerals in the human body, particularly calcium. Phytates, which are present in cereal grains, form an insoluble complex with calcium, making it unavailable for absorption.
Similarly, oxalates can combine with calcium to create insoluble calcium oxalate crystals in the intestine, again inhibiting calcium absorption.
Factors such as a lack of vitamin D, excessive dietary phytates, a low calcium-to-phosphorus ratio in the diet, increased intestinal pH, and malabsorption syndromes can all negatively impact calcium absorption. Therefore, the answer to the given question is: C) calcium.
Additionally, it is worth noting that these substances can also reduce iron absorption by forming insoluble compounds with it.
Vitamin D plays a crucial role in promoting the synthesis of a calcium-binding protein which aids in the active transport of calcium across the intestinal mucosa.