Iron: The iron contained in animal foods, such as liver, animal blood, meat and fish, is heme iron, also called ferrous iron, which can be directly absorbed by the intestine. The iron contained in cereals, fruits, vegetables, beans and milk and eggs in animal foods is non-heme iron, which is also called high iron and exists in the form of complex. The organic part of the complex is protein, amino acids or organic acids. This iron must be separated from the organic acids under the action of gastric acid to become ferrous ions before it can be absorbed by the intestine. Therefore, iron in animal food is easier to absorb than iron in plant food. In order to prevent iron deficiency, animal food should be the first choice.
Zinc: Beef, pork, mutton, fish and oysters in animal foods contain high zinc content. Vegetables and flour in plant foods contain less zinc and are difficult to absorb.
Foods with calcium content greater than 300mg per100g include kelp, laver, Nostoc flagelliforme, auricularia auricula, black sesame and other black foods, and some even have calcium content as high as thousands of milligrams, while the calcium content of milk is only at a medium level, with calcium content of about100g.