Final answer:
Less than 20 percent of dietary iron is absorbed on average, with absorption from mixed diets being more efficient than from vegetarian diets due to the presence of heme iron in animal products.
Step-by-step explanation:
The percentage of dietary iron absorbed from mixed diets is significantly higher than that from vegetarian diets. On average, less than 20 percent of the iron we consume is absorbed. This is due to different types of iron in our diet, with heme iron, found in animal foods such as meat, poultry, and fish, being absorbed more efficiently than non-heme iron from plant sources.
For those consuming a mixed diet including meat, the percentage of absorbed dietary iron is better compared to a strictly vegetarian diet, where the absorption of non-heme iron is less efficient. The body's ability to absorb iron is sophisticated, involving the protein compounds ferritin and hemosiderin for storage, and ferroportin for transporting iron across the intestinal cell plasma membranes and from storage sites into the bloodstream.
Therefore, the correct answer to the question of what percentage of dietary iron is absorbed from mixed diets versus vegetarian diets is that less than 20% is absorbed in general, and the absorption from vegetarian diets can be expected to be lower than from diets that include meat.