Unexpected reactivity of silica places question mark over safety of food additives
Discovery that silica particles – thought to be inert – can oxidise thiols requires further investigation
Pure silica particles – which were thought to be inert and are widely used in food and cosmetics – can facilitate oxidation of cell-protecting antioxidant thiol molecules by converting them to disulfides. Although the study did not investigate the reaction in vivo, the team suggests its findings are concerning and recommends further studies to determine their safety.
‘Thiol-containing compounds, such as glutathione, are biologically important as antioxidants. If the depletion of thiols by silica occurs in the human body, it could lead to toxicity, diseases and ageing,’ explains Yangjie Li, who led the study in Richard Zare’s lab at Stanford University in the US.
The US Food and Drug Administration allows up to 2% by weight of silica particles, also known as silicon dioxide, to be added to food. Meanwhile, the EU allows up to 1% by weight in dried powdered additives in foods. It’s mainly used as an anti-caking agent in dry products such as flours, spices and powders.