Too much or too little iron intake may have a significant impact on the brain, increasing the risk of Parkinson's disease, according to a US team.
A new animal study is the first to demonstrate that both iron deficiency and toxicity are linked to the specific genes and neuronal suicide that lead to dopamine shortages responsible for development of Parkinson's, says researcher Cathy Levenson from Florida State University.
Parkinson's disease is a degenerative condition affecting movement and balance in more than 1 million Americans each year. The prevalence is expected to increase in ageing populations.
In the research, to appear in an upcoming edition of Experimental Neurology, both healthy mice and those at risk for the disease were fed varying amounts of iron.
High levels of iron caused Parkinson's-like symptoms even in healthy mice without apparent risk factors for the illness. They accelerated the decline and death of those already diagnosed with the disease.
In contrast, low levels of iron delayed onset of Parkinson's in mice with risk factors and slowed progress of the disease in those already infected. But the low iron news was mixed.
Levenson also discovered that iron deficiencies in healthy risk-free rodents led to decreasing levels of dopamine, the neurotransmitter critical to relaying brain messages that control both balance and movement.
Dopamine levels fall as the brain cells or neurons responsible for transporting it begin to 'commit suicide' at higher-than normal-rates, triggering the chain of events that eventually precipitates the onset of Parkinson's disease.
The study confirms that both iron deficiency and toxicity are linked to the specific genes and neuronal suicide that lead to dopamine shortages responsible for development of Parkinson's.
"The mouse is a good model for humans as it produces dopamine in the same way as the human brain," Levenson told NutraIngredients.com. "What this shows us is that iron deficiency is not only linked to anaemia and fatigue, but also a problem for the brain and risk for Parkinson's. This has not been recognized until now," she added.
Researchers reported last year that high intake of iron, especially in combination with high manganese intake, may be related to risk for Parkinson's disease.
People who had higher than average dietary iron intake and who also took, on average, one or more multivitamins or iron supplements per day were 2.1 times more likely to be Parkinson's patients than those who had lower than average dietary iron intake and who took fewer than one multivitamin or iron supplement per day.
Levenson said her findings show that people should not self-prescribe iron supplements but should wait until a doctor notifies them of a deficiency.
"I'd be nervous about just handing someone iron supplement...Self-medicating may have unintended consequences," she said.