Calcium from low-oxalate vegetable greens, such as kale, is absorbed as well or better than calcium from cow's milk. Calcium deficiency in vegetarians is rare, and there is little evidence to show that calcium intakes below the Recommended Dietary Allowance cause major health problems in vegetarians. U.S. recommendations for calcium are relatively high compared to those for populations that eat a more plant-based diet. High levels of animal protein increase urinary loss of calcium. U.S. recommendations are designed to compensate for this.
Studies show that vegetarians absorb and retain more calcium from food than do nonvegetarians.
Iron combines with protein to form hemoglobin, the substance in the blood that carries oxygen and carbon dioxide. An adequate intake of iron is necessary to prevent anemia. Many Americans, both meat-eaters and vegetarians, have a difficult time consuming enough iron. Iron is found in animal and plant foods, but the iron in animal foods is more easily absorbed by the body. Also, the iron in plant foods may be less available to the body because of their high fiber content.