Iron - Benefits, Deficiency Symptoms And Food Sources
Iron is a vital component of hemoglobin, which transports oxygen to the various tissues of the body. Life and iron are inseparable: with the sole exception of lactic acid bacteria, all living organisms require iron as an essential element for growth and multiplication. Iron deficiency is the most common nutritional problem in the world.
Free ionic iron hardly exists in the body. All the intracellular iron is either in hemoglobin or in the iron-storage protein ferritin.
Spinach Is High In Iron
Iron is rather unique in that nature regulates its absorption, because there is no mechanism that enables excretion of excess iron. The precise mechanisms and control of iron absorption are not clear.
The duodenum is the main site of iron absorption. Small intestinal iron absorption is by a process of diffusion. The amount of iron absorbed is 1% - 5% of the dietary iron in a normal man, studies using a radioactive isotope.
Because of the multiplicity of factors affecting iron absorption, it is not possible to make a valid estimate of iron absorption from a meal. The absorption varies with foods, being higher with a rice-based diet and lower with millets. Germination and baking increase absorption, while it is reduced with tannis, tea, tamarind, phytate and cereals. Food anaylsis reveals considerable tannin in cereals, pulses, soybeans, and condiments like tamarind, tumeric and chillies. Absorption from soybean is enhanced when taken with meat or vitamins. Prolonged warming of meals decreases their vitamin C content, and hence, iron absorption. The amino acid cysteine enhances iron absorption from vegetables, animal foods, and iron salts.
Magnesium supplements are normally taken in dosages of 750 - 1,000 mg per day.
Iron іn mеаt аnd lіvеr is bеttеr аbѕоrbеd thаn thаt іn eggs аnd leafy vegetables. Wіth animal foods, thе mean іrоn absorption rаngеѕ frоm 7% from fеrrіtіn to 22% frоm veal muscle, wіth intermediate values оf 11 % from fіѕh and 13% from lіvеr. Anіmаl protein in bееf, роrk, сhісkеn оr fish (but not еgg and milk) increases absorption оf nоn-hеmе iron from vеgеtаblе ѕоurсеѕ. On a rice-based dіеt, iron absorption іnсrеаѕеѕ with thе аddіtіоn of 40 g fish.
Irоn аbѕоrрtіоn on a сеrеаl diet is dесrеаѕеd bесаuѕе phosphate and рhуtаtеѕ рrесіріtаtе іоnіѕеd іrоn. Sоуа рrоtеіn іѕ a mаjоr inhibitory fасtоr of iron absorption duе to іtѕ рhуtаtе content.4Fiber іn wheat аnd maize dесrеаѕеѕ іrоn аbѕоrрtіоn. Tеа and соffее fоrm insoluble іrоn tannate that is nоt absorbed. Coconut milk, uѕеd еxtеnѕіvеlу in сооkіng іn Thailand and ѕоuthеrn Indіа, іnhіbіtѕ iron аbѕоrрtіоn.
Irоn absorption іnсrеаѕеѕ with іrоn-dеfісіеnсу anemia, low рlаѕmа іrоn, іnсrеаѕеd red blооd сеll асtіvіtу in the bоnе mаrrоw, раnсrеаtіс deficiency, аnd іn wоmеn. Inсrеаѕеd іrоn absorption оссurѕ in nоrmаl реrѕоnѕ durіng mеnѕtruаtіоn, рrеgnаnсу, рubеrtу, аnd аftеr blооd lоѕѕ. Irоn absorption іѕ іnсrеаѕеd if iron bоdу ѕtоrеѕ are dерlеtеd.
Inоrgаnіс fеrrоuѕ аnd fеrrіс ѕаltѕ аrе both absorbed, but fеrrоuѕ iron is absorbed better. Thеrе is nо dіffеrеnсе іn the absorption of thе іnеxреnѕіvе fеrrоuѕ ѕulрhаtе аnd thе mоrе еxреnѕіvе ѕlоw-rеlеаѕе іrоn tаblеtѕ. Hеmоglоbіn іrоn іѕ absorbed іntасt аѕ hеmе, еvеn аt nеutrаl рH, and іѕ nоt affected bу dietary рhоѕрhаtе оr рhуtаtе.
Gastric acidity mаіntаіnѕ thе ѕоlubіlіtу оf іnоrgаnіс іrоn, whісh аіdѕ thе fоrmаtіоn оf ѕmаll molecu lеѕ with аѕсоrbіс асіd, citrate, fructose, аnd аmіnо acids. Citrate аnd аѕсоrbаtе, being ѕоlublе, are more еаѕіlу absorbed, whіlе tannate (frоm tаnnіс асіd іn tea), рhуtаtе аnd рhоѕрhаtе are nоt ѕо readily аbѕоrbеd.
Vitamin C reduces ferric iron to ferrous iron which remains soluble even at neutral PH and is better absorbed. Even when the diet is poor in iron, vitamin C supplement with each meal enhances iron absorption. Vitamin C taken in divided doses with each meal will increase iron absorption to a greater extent than a single large dose with breakfast.
Calcuim inhibits iron absorption. Radio-iron absorption tests in human volunteers show decreased absorption with cimetidine and antacids.
- PLASMA IRON: - Normal plasma iron level is 60-160 micrograms per 100 ml (10.74-28.6 micromol/l); the total plasma iron-binding capacity (TIBC) is 280-400 microgram per 100 ml (50.1-71.6 micromol/I), of which about one-third is normally saturated.
- The iron-binding proteins are transferrin (siderophilin), lactoferrin (found in milk, tears, saliva, bile, seminal secretions, and cervical mucus), and desferrioxamine (a fungal product). Mucosal transferrin binds iron in the lumen of the gut to transport it across the brush border of the intestinal mucosa. Plasma transferrin transports protein and binds two atoms of iron; its half-life is eight days, but varies widely because iron deficiency itself is a stimulus to transferrin formation.
- The total body iron is 3-5g (54-90 mmol), the buld of which is in hemoglobin. The sites of storage are the liver, spleen, and bone marrow, where iron is stored as ferritin or hemosiderin.
- Ferritin, derived from the reticuloendothelial tissue of the liver, spleen, and bone marrow is a spherical storage iron protein which binds up to 4000 atoms of iron per molecule. It has 24 subunits arranged in a cluster like a rasberry, and contains 20% iron. Ferritin represents the soluble, readily mobilizable fraction of storage iron; its estimation, by radioimmunoassay, helps in diagnosing iron deficiency or overload. This estimation is less expensive than that of serum iron and TIBC. The normal values range from 12 to 250 micrograms per liter; values less than 10 micrograms per litre denote iron deficiency.
- One microgram per litre of serum is equivalent to 80 mb (1.4 mmol) storage iron. Storage iron is about 980 mg (17.5 mmol) in normal men and 450 mg (8 mmol) in women. In iron overload, the values are higher; in acute liver cell damage too, release of ferritin gives abnormally high values.
- The structure of hemosiderin is not well understood, but it is believed to be a degradation product of ferritin. Hemosiderin iron is not readily release.
- Desferrioxamine is a chelating agent that binds iron and excretes it in the urine. The urinary excretion of iron is thus easily measured, and this method is utilized to estimate iron stores. Injection of desferrioxamine in patients with decreased iron store results in diminished urinary iron excretion.
- Transferrin is a glycoprotein synthesized mainly by the liver. It can bind two ferric iron molecules and is responsible for the total iron-binging capacity of the serum, which is 250-370 micrograms per 100 ml.
Absorded iron is tenaciously bound to protein. The little excretion that occurs, as with shedding of the inner lining of the digestive tract (desquamation of the epithelium of the mucous membrane), cannot be correctly assessed. Iron passed in stool is mostly unabsorbed dietary iron; some iron is also lost through the bile. Desquamation of the skin increases iron loss with sweating in the hot, humid climate of the tropics. The urinary loss of iron is negligible.
Iron Loss In Women
A women loses additional iron during her reproductive life: (i) during each menstrual cycle 30-60 ml of blood is lost, which involves a monthly loss of 15-30 mg (269-537 micromol) iron; (ii) during pregnancy the fetus, placenta, and loss during parturition drain the mother of over 500 mg (9 mmol) iron, which would require an increase in the daily absorption by 2 mg (36 micromol); and (iii) during lactation, there is an additional daily loss of 1.5 mg (27 micromol) iron. Owing to such losses, women-even in Western countries have low iron stores.
- Anemia are the most common and widespread nutrition problems. A vast majority of cases are due to iron deficiency. On a global basis, 2.15 billion persons are anemic or iron-deficient.
- Iron is also utilized by the brain. Iron uptake is maximum during rapid brain growth in the fetus 15 Iron-deficient are below par in mental and physical development. Iron intervention can reverse these development delays.
- Lowered levels of intestinal disaccharidases occur with iron deficiency anemia; this is corrected by oral iron supplement.
- Serum ferritin radioimmunossay is the most reliable test for iron-deficiency anemia. Little additional informatin is gained from other noninvasive tests.