Final answer:
Calcium-rich foods, phytates in cereals and grains, as well as tea and coffee consumption, can decrease iron absorption. To increase it, include vitamin C sources and cook in iron utensils. Excessive supplemental iron should be avoided.
Step-by-step explanation:
Examples of foods and conditions that decrease iron absorption include calcium-rich foods, such as dairy products or supplements, due to their tendency to form insoluble salts with iron. Consumption of foods high in phytates, which are found in cereals and grains, and drinking beverages such as tea and coffee, which contain polyphenols, can also inhibit iron absorption. Other dietary components like oxalates and excess fiber can reduce iron absorption as well, along with certain health conditions like achlorhydria (lack of stomach acid) and copper deficiency.
To enhance iron absorption, it is recommended to include sources of vitamin C and heme iron, such as meats, as they can form soluble complexes with iron. Cooking in iron utensils can also fortify food with iron through physical inclusion of the metal, which is later absorbed as Fe²+ ions. However, excessive intake of supplemental iron without medical supervision can lead to imbalances and should be avoided.