Iron fortification & health risks
Iron is an essential mineral required for many bodily functions, including the formation of hemoglobin, but can be harmful when taken in excess.
One of the methods suggested for the treatment of iron deficiency anemia is fortification of food with iron.
- Typically, a chosen food staple like wheat or rice, or even salt, is fortified to provide up to two thirds (10 mg/day) of the iron requirement of adult women, and almost the entire daily requirement of men.
- When combined with additional iron supplemental interventions like weekly iron folic acid supplements (such as in the National Iron Plus Initiative programme), this can lead to an excess of iron intake for women.
- There is a defined level of iron intake beyond which the risk of adverse events begins to increase.
- This is called the ‘tolerable upper limit’ of intake, and is set at 40 mg/day.
- Nevertheless, the excess iron in the fortified diet can remain unabsorbed. Typically, it is expected that just 5-10% of the ingested iron, from the iron salt that is added, is absorbed.
- The rest passes on through the intestine and reaches the large intestine (colon) prior to excretion. Studies have shown that unabsorbed iron can lead to inflammation in the gastrointestinal lining and disrupt the colonic microbiota with long term consequences.
- This is due to a proliferation of iron-living bacteria in the colonic microbiome, and a reduction of beneficial strains like lactobacteria, with the appearance of some bacterial strains that could be pathogenic. This irritation of the lining may present itself clinically as abdominal cramps, constipation, or diarrhoea.
- In addition, the irritation of mucosa can also lead to gastrointestinal blood loss, as has been described in endoscopic studies of patients on iron supplementation. An excess of iron in the gastrointestinal tract can impair absorption of other minerals such as zinc and copper, which are also essential for the body and lead to other deficiencies.
- A more pressing worry is that excess iron has been closely linked to many chronic comorbidities like diabetes.
- This is attributed to many causes, including oxidative damage and beta cell destruction by reactive oxygen species (ROS) which could lead to decreased insulin secretion. Iron can generate ROS and lead to oxidative stress in the body.
- In very high amounts, iron also has a role to play in the hepatic stellate cell (HSC) activation and excessive deposition of extracellular matrix in the liver. This can lead to liver fibrosis, with subsequent progression to cirrhosis. When liver iron concentration (LIC) exceeds a threshold of 60 µmol/g, HSC function starts to deteriorate, and cirrhosis can occur at LIC levels above 250 µmol/g.
- Rather than adopting mandatory iron fortification programmes where unsupervised high iron intakes are instituted across a diverse population, it is imperative to develop individualised strategies and ensure thorough monitoring to detect any adverse events at the earliest. There is no doubt that some segments of the population need the extra dietary iron but not all.
- Eventually, precision in public health is essential if we are to avoid the risk of iron overload and the potential for long-term chronic illnesses due to excess iron.
- As a public health strategy, the pendulum should not swing all the way to the other side.
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