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The Iron discussion

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Klaas Feenstra

New Member
Jun 4, 2002
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A couple of weeks ago, there was an discussion about Iron deficiency in freedivers in the 138m With out Fins tread. Here is my response at some of the raised questions.

The Physiological role of Iron in the body.

Iron doesn’t have only a vital role as a carrier of oxygen to the tissues from the lungs; it is also important as a transport medium for electrons within cells and as an integrated part of important enzyme reactions in various tissues.
To illustrate this, I will give the figures where the Iron is in a average 75kg Male; there is about 4000mg Iron in the whole body, 73% of that is functional iron, the rest is iron stored in Ferritin and Haemosiderin. The functional Iron can be divided in four groups, respectively Haemoglobin (60%), Myoglobin (9%), Haem and non-haem enzymes (4%) and Transferrin-bound Iron (>1%), all percentage are from the available total iron.

Iron metabolism exist of two loops, one external and one internal, respectively the iron in the red blood cells which normally die and are replaced after 120 days and where Iron is re-used through macrophages and transferrin transport. Iron is lost by cell losses, including bleeding and the continue process of replacing the surfaces of the body.

On a average level, 18+ males need a median absorbed dose of 1.05 mg/day, 18+ females need a median absorbed dose of 1.46 mg/day.

Iron Absorption

There are two kinds of iron in the diet with respect to the mechanism of absorption – haem iron and non-haem iron, utilising two separate types of receptor on the mucosal cells.

The amount of uptake is dependent of Dietary factors, summarising:

Haem iron absorption
- Amount of haem iron present in meat
- Content of calcium in meal. Calcium inhibits iron uptake
- Food preparation (time, temperature), Higher temperature and longer time degrades haem iron into non-haem iron

Non-haem iron absorption
- Iron status in subjects (Iron deficit subjects will uptake more Iron a normal subject)
- Amount of bio available non-heam iron (adjustment for fortification and contamination iron)
- Balance between dietary factors enhancing and inhibiting iron absorption

Factors enhancing iron absorption
- Ascorbic Acid
- Meat, Fish, Seafood (Iron supplements intake with Meat, Fish and Seafood, is by an unknown process better absorbed than without)
- Certain organic acids

Factors inhibiting iron absorption
- Phylates (Bran, Bread, Oats, can be partially counteracted by Ascorbic Acid)
- Iron-binding phenolic compounds (tea, coffee, cocoa, spinach, several herbs and spices)
- Calcium (Milk, cheese etc.)
- Soy protein

It could be concluded that concerning iron absorption is dependant of the overall diet. For example, it is none that especially in developing countries, drinking tea with main meals is probably an important factor contributing to a high prevalence and severity of Iron deficiency.

Iron Deficiency and Iron-Deficiency Anaemia

These concepts are often incorrectly used as synonyms. Commonly, iron deficiency refers to the lack of iron available in the body, or available by absorption. In Iron-Deficiency Anaemia, there is not enough Iron available for the red bloodcells, for example due to a transferrin related problem. It can be caused by Iron Deficiency, but it doesn't have to. Measuring Hb/Ht doesn't really give a clear figure what the amount of ferrine in the body is, and if it is the cause to an anaemia.

Causes of iron deficiency

The most common cause of iron deficiency is a nutritional deficiency. Nutritional iron deficiency implies that the diet cannot cover physiological iron requirements. World-wide, this is the most common cause of iron deficiency, although there are also pathological causes as, but not limited to hookworm, gluten enteropathy or in patients who undergone gastric surgery.

Deleterious effects of iron deficiency

In summary, the effects of iron deficiency are larger then only the well-known anaemia. There is also an relationship between iron deficiency and brain function and the immunological response of the T-lymphocytes can become impaired (phagocytosis and killing of bacteria).

Treatment

The cause of an iron-deficiency anaemia may be purely nutritional, i.e. the diet cannot cover the physiological losses of the subject. To treat a patient with a moderate iron-deficiency anaemia only by improving the diet would take a very long time, probably several years. A good diet is important for the prevention of iron deficiency but is not sufficient for the treatment of an existing iron-deficiency anaemia. Oral iron therapy is usually very effective if well absorbed iron tablets are given at sufficient dosage for a sufficiently long time.

Motivating the patient, by explaining why and how the tablets should be taken, is essential for an effective treatment. Sometimes a therapeutic failure is caused by the poor properties of the iron tablets. The coating of iron tablets must be sufficiently good to prevent oxidation of the ferrous iron to ferric, but at the same time not too resistant to allow the tablets to disintegrate and be dissolved in the gastrointestinal tract.

Parental iron preparations an also be used. Because of their potentially more sever side-effects and risks, they should only be used in patients who cannot absorb iron because of malabsorption, in patients with inflammatory intestinal disorders and in patiens with more marked side-effects from oral iron, such as consistent nausea and epigastric pain which cannot be ameliorated by reducing the dose of oral iron.

On overdose of iron:

Unbelievable or not, even iron can lethal in to high dosages. The acute lethal dose in adults is at 180-300 mg iron per kg body weight. You can’t live without Iron, but too much can kill you in a very nasty way.

:hmm As a Final note; This reply on the topic should not be used as a blueprint for treatment of anaemia. If you are anaemic and have problems with it, the person you should see is your General Practitioner, who can a. treat you better than with the most iron tablets found in the average store, and b. can exclude any pathological cause to anaemia.

Just my 0.2 cents,

‘Houten’ Klaas

Sources:
JS Garrow, WPT James and A Ralph. Human Nutrition and Dietetics, 10th edition, published by Churchill Livingstone, London pg. 177-192
CH, Farmacotherapeutisch Komas 2002 pg. 213-218
RS Cotran, V Kumar and T Collins. Robbins Pathologic Basis of Disease, 6th edition, published by W.B. Saunders Company, London, pg. 627-630
 
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SThompson

Nekton Pelagic
Apr 15, 2002
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:) EXCELLENT post!! I remember the thread you are talking about, and have to thank you for taking the time to put together all of this information. This is exactly some of the info that I come to this forum to get.
 
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