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IRON: Natural Dietary Sources

IRON: Natural Dietary Sources
Iron is an essential dietary mineral required by our body to make two very important proteins namely haemoglobin and myoglobin.
Haemoglobin is a protein found in red blood cells that is responsible for carrying oxygen from the lungs to all other parts of the body.
Myoglobin is a protein found in muscles whose purpose is to provide oxygen to muscles.
We get our daily requirement of iron through our diet. Iron from the ingested food is absorbed in the duodenum and proximal jejunum (part of the small intestine) and from here, it is transported throughout the body by a protein in the blood called transferrin. Our body also stores iron in the liver, spleen, muscles and bone marrow in form of ferritin.

Recommended Dietary Allowances for Iron

Age Male Female Pregnancy Lactation
0 – 6 months 0.27 mg 0.27 mg
7 – 12 months 11 mg 11 mg
1 – 3 years 7 mg 7 mg
4 – 8 years 10 mg 10 mg
9 – 13 years 8 mg 8 mg
14 – 18 years 11 mg 15 mg
19 – 50 years 8 mg 18 mg 27 mg 10 mg
51 + years 8 mg 8 mg

SOURCES OF IRON :
Iron we get from our food comes in two forms: heme and non-heme.
  1. Heme iron – It comes into our diet only from animal food like poultry, meat and seafood this is because it is only found in blood and muscles. Also, it is easy to be absorbed by the body as compared to non-heme iron.
  2. Non-heme iron – It comes into our diet from plant-based foods like fruits, vegetables, green leafy vegetables, whole grains, nuts, seeds and legumes. Along with this, non-heme iron is found also found in animal-based foods (like dairy or eggs as some animals eat plants) and iron-fortified foods. Therefore, we can say
  • Animal meat is a combination of both heme (40%-45%) and non-heme (55%-60%) iron.
  • Plant-based foods have non-heme iron only.
  • Eggs and dairy products also have non-heme iron only.

Source (Vegetarian) Serving Milligrams of iron per serving Daily Value(DV)
Moringa leaf powder 100 grams 28 mg 168 %
Spinach 100 grams 2.7 mg 15 %
Cashews almonds 100 grams 2.8 – 5.9 mg 16 – 33 %
Potato 1 large unpeeled, 300 grams 3.2 mg 18 %
Legumes (Beans, soybeans, chickpeas, peas and lentils) 1 cooked cup, 198 grams 6.6 mg 37 %
Pumpkin seeds, sesame seeds, flaxseeds 1 ounce, 28.5 grams, 2 tablespoon 1.7 – 3.9 mg 9 – 22 %
Broccoli 1 cooked cup, 156 grams 1 mg 6 %
Dark chocolate 1 ounce, 28.5 grams 3.4 mg 19 %
Tomato 1 cup puree, 250 grams 4.5 mg 26 %
Sweet potato 100 grams 0.6 mg 4 %
Beetroot 100 grams 0.8 mg 4.4 %
White mushrooms 11 cooked cup, 156 grams 2.7 mg 15 %
Apple 1 medium 0.3 mg 2 %
Pomegranate 100 grams 0.3 mg 2 %

Source (Non-Vegetarian) Serving Milligrams of iron per serving Daily Value(DV)
Chicken breast 100 grams 0.7 mg 4.3 %
Ground beef / red meat 100 grams 2.7 mg 15 %
Chicken liver 100 grams 9 mg 54 %
Beef liver 100 grams 6.5  mg 36 %
Mackerel 1 cooked fillet 1.4 mg 7 %
Salmon 1 cooked fillet 2.2 mg 13 % %
Clams 100 grams 28 mg 168%
Chicken eggs 2 large eggs 1.9 mg 11 %
Prawns 100 mg 3 mg 17 %
Pork 100 grams 1.3 mg 7 %
Lamb 100 grams 2 mg 12 %

Function of Iron
  1. Hemoglobin synthesis– Haemoglobin is a protein that is responsible for transporting oxygen in the body. It is made of iron (heme) and protein (globin).
  2. Myoglobin synthesis– It is a protein found in muscles which are responsible for the red color of muscles and it stores oxygen in muscles.
  3. Hormones and enzymes synthesis
  4. Proper functioning of the immune system

Factors affecting iron absorption
A normal healthy body absorbs 18% iron from the animal-based diet and 10% from plant-based. But, our body may be absorbing lesser quantities even if we are having iron-rich food. This may be because our stored iron reserves have a sufficient amount of iron. Similarly, if our body has low iron stores, it will automatically absorb larger quantities of iron.
Certain foods boost iron absorption in our bodies. Like
  1. Vitamin C-rich food
  2. Combining both animal and plant sources of iron. For example- Spinach with beef.
Certain foods reduce iron absorption in the body. Like
  1. Tea, coffee
  2. Calcium
  3. Soy proteins
  4. Phytates and fibers

Iron deficiency
Causes :
  1. Low dietary intake
  2. Increased iron demands like in pregnancy,  lactation
  3. Blood loss – heavy menstruation; chronic blood loss due to peptic ulcers, repeated nose bleeds, cancer
  4. Heavy exercises

At risk groups :
  • Menstruating women
  • Pregnant women
  • An infant who is exclusively breastfeeding
  • Vegetarians
  • Athletes
  • Persons suffering from some chronic disease
  • Intestinal worms

Stages of Iron deficiency :
  • Iron depletion– This is an asymptomatic stage in which blood hemoglobin levels are normal but the stored reserve of iron is low.
  • Iron deficiency– In this stage hemoglobin level drops and iron reserves also become a deficit.
  • Iron deficiency anemia – In this stage hemoglobin levels are so low that the body is unable to transport oxygen to the cells thus producing the following symptoms-
  1. Pale skin
  2. Dizziness
  3. Fatigue
  4. Breathlessness
  5. Confusion
  6. Cold extremities
  7. Pica – strange food cravings like clay and dirt.

Iron Toxicity : 
This is rare as the body regulates iron absorption (I.e. body will absorb less iron if it already has adequate reserves). But if someone takes a high dosage of iron supplements or someone has hemochromatosis (a hereditary condition which leads to an excessive iron build-up in the body) condition of iron toxicity will arise and the following symptoms will be seen
  1. Nausea, vomiting
  2. Constipation
  3. Pain in the abdomen
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Dr C P Ravikumar

CONSULTANT – PEDIATRIC NEUROLOGY
Aster CMI Hospital, Bangalore