Final answer:
Vitamin C, also known as ascorbic acid, increases the absorption of non-heme iron by converting ferric iron to the more soluble ferrous form. The acidic stomach environment and presence of certain proteins in the diet also aid iron absorption. Despite being less commonly absorbed, non-heme iron is essential and is often added to foods as metallic iron due to its stability.
Step-by-step explanation:
The nutrient that increases the absorption of non-heme iron by reducing ferric iron (Fe₃⁺) to ferrous iron (Fe₂⁺) in the human body is ascorbic acid, commonly known as Vitamin C. Ascorbic acid enhances iron absorption by reducing ferric iron to ferrous iron, which is the form that is more readily absorbed in the gut. This is particularly important for non-heme iron, which comes from plant sources and is less efficiently absorbed as compared to heme iron from animal products.
Iron absorption occurs primarily in the duodenum and the proximal jejunum of the small intestine. An acidic environment favours the absorption of iron, which is why ascorbic acid, being a strong reducing agent in the acidic environment of the stomach, promotes the solubility and uptake of non-heme iron. In addition, dietary factors such as the presence of meat, which provides protein, can also enhance iron absorption. Conversely, substances like phytate, present in some grains and beans, can inhibit non-heme iron absorption by forming insoluble complexes with iron.
Importance of Iron in the Diet
Iron fortification in food products like bread and breakfast cereals often involves adding iron in its metallic form because this form is more stable during food processing and storage. Though it may seem counterintuitive, the body can oxidize this metallic iron to Fe₂⁺ in the digestive system where it can then be absorbed. Hence, while Fe₂⁺ salts could be used directly, fortifying food with metallic iron is sometimes preferred for practical reasons.