The iron blockade

Often, I see patients who have been prescribed up to 300 mg of iron daily to treat anaemia. Yet, despite such high supplementation, serum iron levels are not increasing. Why?

More is not necessarily better, particularly in the case of iron. The reason is that in those with iron deficiency, there is a mechanism called the mucosal block.

This is when an initial dose of iron can reduce the absorption of a subsequent dose. Studies have been done on 20 mg, 30 mg and 60 mg as the blocking doses.

Researchers found that a 20 mg dose of iron did not consistently have an effect on a subsequent dose of iron, However, 30 mg and 60 mg blocked a subsequent 10 mg dose given 12–24 hours later either completely or by 46 per cent. So, a 300 mg daily dose would have a significant effect on absorption. This is why in patients on such high doses their levels are not improving, as the mucosal block is constantly switched on.

Further, a Cochrane Review (an independent study which pulls all available evidence together) concluded that intermittent dosing is just as effective as daily administration at reducing the risk of anaemia and iron deficiency and improving the concentration of haemoglobin and ferritin (stored iron), with no side effects.

The side effects of high dose iron supplements are due to the unabsorbed fraction of iron that remains in the gastrointestinal tract, producing free radicals that eventually create inflammation and affect the gut microbial composition and also cause constipation and nausea.

Also, important to bear in mind the type of iron prescribed. Often these super high dose iron supplements contain ferrous sulfate a very unabsorbable form of iron regularly resulting in black stools, constipation and stomach cramps.

Always best to use organic, absorbable forms of iron such as iron amino acid chelate (iron bisglycinate). This form of iron is bound to the smallest amino acid, glycine allowing absorption through the gut mucosa via the most efficient amino acid uptake pathways. There is no dissociation in the digestive tract, minimizing the side effects common amongst other forms of iron.