A new study suggests that changes in the mineral composition of hair could provide clues about Parkinson’s disease. The research indicates that a low level of iron in the hair could be associated with digestive disorders and imbalances of the intestinal microbiota in patients with this condition.
The exact cause of Parkinson’s disease is not known. Previous studies have associated this neurodegenerative disease with changes in gut bacteria and unhealthy diets, including those rich in ultra-processed foods. There is also evidence of a link to environmental pollutants such as pesticides.
Researchers in China have now identified a potential biomarker of Parkinson’s disease in human hair. The team from Hebei University analyzed hair samples from 60 Parkinson’s patients and compared them with samples from healthy people of the same age.
According to the results published in the journal iSciencehair samples from patients with Parkinson’s disease showed significantly lower levels of iron and copper and higher levels of manganese and arsenic compared to the control group. The authors believe that these differences have a high diagnostic potential for Parkinson’s disease.
The diagnosis of Parkinson’s disease by non-invasive methods remains difficult. Although biomarkers identified in blood have been proposed, hair represents a different target with distinct characteristics. Hair can accumulate heavy metals from diet and the environment and, unlike saliva, sweat, blood, urine or faeces, can reflect a longer period of a person’s biological history.
In additional experiments in animal models, the researchers also observed lower levels of iron in hair. This change was closely correlated with intestinal dysfunction. In mice with a condition similar to Parkinson’s disease, the intestinal barrier was damaged. Genes involved in iron absorption had reduced activity, and genes associated with iron capture by microorganisms showed increased activity, which could lead to a generalized iron deficiency in the body.
In the case of human patients, changes in the intestinal microbiota occur years before diagnosis. Data suggest close communication between the gut and the brain in neurological diseases, including Parkinson’s disease. Hair iron deficiency was the most constant and obvious change identified in both patients and animal models.
The authors appreciate that the connection between the intestinal microbiome and the genes involved in iron metabolism represents a proof of concept regarding the connection between these systems in the context of a Parkinson’s type pathology.
Elevated arsenic levels in hair require further investigation as they may reflect exposure to environmental factors. The study has a small number of participants, and patients with Parkinson’s disease reported higher consumption of offal and seafood, foods that may contain arsenic.
The results support the conclusions of another study, published in 2025, which identified evidence of deregulation of iron metabolism at the brain, blood and intestinal level in patients with Parkinson’s disease.
The researchers emphasize that larger cohort studies are needed to confirm these observations and to clarify the mechanisms linking iron deficiency to Parkinson’s disease.
