Iron is one of the most important elements required for body functions, including the production of hemoglobin, immune system support, energy production, and the synthesis of hormones.Â
Sources and Metabolism of Iron
Iron in our diet comes from three different sources:  animal food (such as meat, poultry, and fish), plant food (such as leafy green vegetables, legumes and grains) and cooking utensils of iron. Iron from muscle food is called heme iron as this iron is part of heme group found in hemoglobin and myoglobin. Iron from plant sources and iron utensils is called nonheme iron. Iron from the food is absorbed into the body by the intestinal cells and then released into the blood where it binds to a protein called transferrin that helps  delivering the iron to the liver. Inside liver Iron binds to another protein called ferritin which acts as a storage protein for iron. Iron remain stored in the liver as ferritin unless needed and released to make new red blood cells. Iron from old cells is also recycled by the body.
Forms of Iron and their Bioavailability
The amount of iron absorbed into the gut cells depends upon the type of iron and the dietary components that could either increase or inhibit iron absorption. Compared to nonheme iron, heme iron is more efficiently absorbed and its absorption is not affected by the dietary factors such as phytate, oxalate, and polyphenols. Phytate which mainly comes from grains and legumes is one of the most powerful inhibitors of nonheme iron absorption.  Similarly, polyphenols (found in many cereals, vegetables, tea and coffee) and oxalate (found in green leafy vegetables) substantially interfere with absorption of iron.  This is very important to take into consideration as for vegetarians, grains and vegetables are the main source of iron. It is due to this reason that the iron requirements for vegetarians have been estimated to be 1.8 times higher than the requirement for non-vegetarians.
Dietary Patterns and Iron Deficiency Anemia
Different types of dietary patterns are followed across the globe. A vegetarian diet excludes meat, while a vegan diet excludes all animal products, including meat, dairy, and eggs. A pescatarian diet is a vegetarian diet with fish and seafood while flexitarian or semi vegetarian is a dietary pattern with occasional meat. Despite, the well- known benefits of vegetarian diet, vegetarian are at higher risk of iron deficiency due to low bioavailability of iron from plant based diet.
Iron deficiency can lead to iron deficiency anemia, which results in smaller than normal red blood cells. These cells are not capable of supplying adequate oxygen to cells, tissues, and organs leading to decreased cognition, fatigue, less functional immune system and complications in pregnancy.
Milk Intake and Iron Deficiency
Milk comprise the major portion of children and infants diets. On the other hand, growing children and infants typically need more iron, the recommended amount is about 11 mg/day for infants of six months and 7 mg/day for children of 1-3 years. Excessive consumption of cow’s milk leads to iron deficiency, firstly, because milk has very low iron content (0.5mg/L); secondly milk contains non-heme iron predominantly which is less available; thirdly high calcium and casein contents in cow’s milk  compete with iron and limit absorption of iron from other foods in the digestive tract. It is important to mention that although iron contents in cow’s milk and human breast milk are almost similar, human milk ensures 2.5 times greater iron bioavailability. Therefore, it has been recommended to delay feeding cow’s milk until 1 year of age and avoid excessive intake of milk after 1 year.
How to Improve Iron Absorption while on Vegetarian Diet
Vegetarians can improve their oral iron absorption in number of ways:
- Utilizing iron casts for cooking  has been shown to be an effective way for treating iron deficiency anemia.
- Since absorption of iron is increased when vitamin C and other organic acids are present in the meal, therefore ingesting grains and cereals with fresh citrus fruits could help increase iron availability.
- Due to presence of polyphenols as inhibitor of iron absorption, limiting use of tea and coffee could enhance iron absorption. It is recommended to consume tea and coffee 1-2 hours after meal instead with meal.
- Processing steps in food preparation such as cooking, germination and fermentation could reduce the phytic acid content.
- Since calcium competes with iron absorption, it is recommended to ingest calcium-rich foods in meals with lowest iron content.
For Further Reading
- Patterns of Dietary Iron Intake, Iron Status, and Predictors of Haemoglobin Levels among Early Adolescents in a Rural Ghanaian District
- The Consequence of Excessive Consumption of Cow’s Milk: Protein-Losing Enteropathy with Anasarca in the Course of Iron Deficiency Anemia—Case Reports and a Literature Review
- Iron Absorption: Factors, Limitations, and Improvement Methods
