Giving babies extra iron in the form of fortified formula and cereal prevents anaemia – but could too much help pave the way to Parkinson's disease decades down the track?
It's a question being asked by a group of Australian scientists who suspect that too much iron early in life may harm older brains.
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We need iron for healthy brain function at any age – and it's critical for healthy brain development in the first three years of life – but some research suggests that for ageing brains too much iron can raise the risk of both dementia and Parkinson's disease, says Dr Dominic Hare, from the Florey Institute of Neuroscience and Mental Health at the University of Melbourne.
"I'm not saying iron fortification of food isn't okay – it's been a public health success story that's prevented iron deficiency anaemia in children and promoted healthy brain development," he stresses. "But the body and especially the brain aren't very good at getting rid of excess iron. If the brain is given a head start with too much iron and its 'warehouse' of iron is spilling over as it gets older, there may be a risk that the excess iron will damage brain cells."
It's a controversial idea that not everyone agrees with – but there are some clues pointing in that direction.
"We looked at the numbers of people dying with Parkinson's disease in high-income countries like the US, the UK, Sweden and Australia that introduced iron fortification of foods like flour in the 1930s. The rationale was that it would reduce widespread anaemia, including in babies and children. We've gathered evidence that 60 years on there's a spike in mortality from Parkinson's disease in those countries that's continuing to grow. The exception is Japan which has had no mandatory or voluntary fortification of infant formula, grains or rice," says Hare.
The link between iron overload in the brain and Parkinson's isn't new. It's been around since the 1920s and now a small study by French researchers suggests that a drug that mops up excess iron in the brain improves movement slightly in people with Parkinson's. The next step is a larger study to see if the drug has real potential for treating the disease in its early stages.
Around 25 people each day are diagnosed with Parkinson's – and one in seven of them are under 50 according to the Florey Institute.
The disease occurs when the cells that produce the brain chemical dopamine die off, causing problems with movement.
"Within a year of being diagnosed with Parkinson's disease, over 50 per cent of these brain cells have died – we need a way of identifying people at risk of the disease before that happens and a test that can detect early exposure to excessive iron may be a way of doing that," says Hare.
Iron fortification is important for children who need it, he says. But should we reconsider how much iron is added to infant formula and cereals made for children, given that babies starting solid foods in affluent countries like Australia now have a range of naturally iron rich sources of foods including meat and leafy vegetables, as well as iron fortified formula?
Hare also points to a 2012 study comparing healthy Chilean children who had received low iron formula (with 2.3mg iron per litre) with children who had received formula fortified with 12.7mg of iron per litre.
"When they were followed up 10 years later, the children with the higher iron formula scored lower on a range of tests measuring healthy neurodevelopment, including intelligence, learning and, most importantly, motor skills," he says.
The study concluded that "optimal amounts of iron in infant formula warrant further study".
"At the moment we don't know what the optimal amount of iron in formula should be and levels vary in different countries. There's a growing number of voices saying 'hang on, let's find out what the right level should be'," Hare says, adding that recent World Health Organisation guidelines on iron supplementation for children say that a research priority should be collecting more data on the safety of iron supplementation, including the effects on non-iron deficient children.
Formula in Australia is required to have a minimum of 5.5mg iron per litre and a maximum of 13.6mg per litre. This compares to 12mg per litre in the US and a range of 1.9mg per litre to 8.5mg per litre set by the European Commission. Although infant formula recommendations are being reviewed by Food Standards Australia New Zealand, a spokesperson for FSANZ says that while the upper limit for iron is higher than some international recommendations it's unlikely to pose a risk to infant health.
As for understanding the link between iron and Parkinson's and Alzheimer's disease – and other brain diseases including motor neurone disease – that's a work in progress, says Professor Perminder Sachdev, Co-Director of the Centre for Healthy Brain Ageing (CHeBA) at the University of NSW.
With Alzheimer's disease, for example, there's some evidence that iron-deficiency may be protective – but it's inconclusive, he says.
"More work needs to be done before we have definitive information about whether targeting iron may have benefits for treating or preventing Alzheimer's."