Five Important Facts about Iron

ID-10070014Iron is an important mineral for our body and optimal health. Iron is present in hemoglobin, which is responsible for transport of oxygen to various tissues and cells of the body to maintain normal functioning of our body.

Our normal daily diet contain 10-20 mg of iron. Iron is absorbed from all over the intestine, but mostly from upper intestine (stomach and duodenum). Iron is present in diet in two forms, heme form (or organic form) and inorganic form (inorganic form is absorbed approximately 5% and heme form is 35% is absorbed). Heme form or organic form is better absorbed, but only a small percentage of dietary iron is heme form. Heme form is absorbed directly from intestine, but inorganic form has to be reduced to heme form before absorption and a lesser percentage is absorbed as a result.

How much iron our body contains?

Human body contains 2.5-5 grams of iron. Out of the total iron two thirds (approximately 66%) is present in hemoglobin, 25% present in iron stores (ferritin and hemosiderin), 6% as parenchymal iron as part of various enzymes, and 3% is present in muscles as myoglobin.  

How much iron we need?

Our average diet contains 10-20 mg of iron. However, only a fraction of dietary iron is actually absorbed. The daily requirement of iron for:

  • Adult male: approximately 1mg per day
  • Adult female (menstruating): approximately 2 mg per day
  • During pregnancy: 3-5 mg per day
  • Infants: 60 microgram per kilo body weight per day
  • Children¬† 25 microgram per kilo body weight per day

The above-mentioned requirement is the actual iron that needs to be absorbed from diet or supplements. Different authors may give different daily RDA (recommended daily allowance) of iron, such as daily requirement for adult male as 10-15 mg per day, which is actually the amount of iron present in diet, all of which is not absorbed and only a small percentage is absorbed (e.g. approximately 5% for vegetarians and 15-20% for non-vegetarians).

What factors facilitates better iron absorption?

  • Acid (including gastric hydrochloric acid, this is one of the reason why meat helps in better iron absorption as meat eating leads to increase acid secretion in stomach, also meat contain more heme iron and amino acids, which are also reducing substances) or any reducing substance which can reduce ferric form of iron to ferrous form.
  • Iron is better absorbed on empty stomach, but iron supplements are given after food/meal because oral iron cause gastric irritation if given on empty stomach.

What factors reduce iron absorption?

  • Alkali, including antacids (contain alkali), which prevent reduction of inorganic iron to organic form and prevent absorption.
  • Presence of certain substances such as phytates (present in wheat and maize), phosphates (rich in egg yolk), which forms complex with iron and make iron unavailable for absorption
  • Drugs such as tetracyclines
  • Presence of other foods in stomach

Food sources of iron:

  • Rich food sources of iron include liver, egg, oyster, dry beans, dry fruits, yeast, wheat germ etc.
  • Food sources with medium iron content are meat, fish, poultry, banana, spinach (and other green leafy vegetables), apple etc.
  • Poor food sources of iron are milk and milk products (unless fortified with iron), root vegetables etc.

Image courtesy of imagerymajestic / FreeDigitalPhotos.net

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