Mollusks, like clams, oysters and mussels, offer the most naturally-derived, animal-based iron per bite. A serving of 100 grams of mollusks has 28 milligrams of iron, or about 155 percent of the recommended daily value for adults.
According to WebMD, there are two types of dietary iron: heme and nonheme. Heme iron is derived from animal sources, and nonheme from plant sources. According to the CDC, heme iron is two to three times more easily absorbed by the body than nonheme iron. Liver and mollusks offer the most heme iron per serving. Cooked beef, canned sardines and cooked turkey are also rich in heme iron. Squash, nuts, lentils, beans and spinach are all foods high in nonheme iron. There are many foods enriched with iron available, such as bread and cereals. Iron-enriched foods contain a processed form of nonheme iron.
Certain foods can hinder or help iron absorption, such as those that contain caffeine and calcium. Avoid foods or supplements containing calcium and caffeine while eating iron-rich foods. To maximize how much iron is absorbed by the body, eat iron-rich foods with foods or drinks containing vitamin C, such as broccoli or orange juice. Eating a variety of iron-rich foods throughout the day also maximizes iron absorption.