Recent studies have proposed a role for diet in Parkinson's disease (PD). PD is characterized by a high deposition of iron and a low concentration of ferritin in the substantia nigra. Few data in the literature are available on the possible role of dietary iron in the development of PD.
In a population-based, case-control study, we addressed the hypothesis that high dietary iron intake was associated with PD. We assessed dietary iron intake with a semiquantitative food-frequency questionnaire in 104 PD patients and 352 control subjects, frequency matched for age and gender. We also studied the association of PD and dietary iron and animal fat intake in the presence of different iron stores measured by transferrin saturation.
No significant differences were observed between patients' and control subjects' dietary intake of iron from food or supplements (odds ratio [OR] for the highest quartile of intake, 0.9; 95% confidence interval [95% CI], 0.6, 1.3; p for trend = 0.60). Among those with low transferrin saturation levels (lower 50%), the odds ratio for PD associated with animal fat intake was ninefold higher than the risk of those with low intake (OR, 9.0; 95% CI, 2.7-29.9). Among those with high transferrin saturation, risk of PD was two times higher (relative risk, 1.9; 95% CI, 0.5-7.2) for those who reported high intake of animal fat compared with those who reported low intake.
Dietary iron intake after caloric adjustment was not associated with an increased risk of PD. However, the previously described association between animal fat intake and PD was modified by iron level stores as measured by transferrin saturation. These observations suggest that dietary fat and a systemic defect in iron metabolism may act synergistically in the process of lipid peroxidation in PD.