EFSA questions nano silver safety in supplements

By Shane Starling

- Last updated on GMT

Related tags: Nanotechnology, European food safety authority

The European Food Safety Authority (EFSA) has said there is insufficient evidence to determine the safety of nanotech, silver hydrosols in food supplements.

The opinion will influence whether the nutrient is added to annex II of the Food Supplements Directive (FSD), a decision that has to be made by the European Commission and Member States by the end of 2009.

If the nano-nutrient, said to have immune system boosting properties, can be shown to be safe and efficacious it will remain on the market.

In its ruling EFSA’s Panel on Food Additives and Nutrient Sources added to Food (ANS) said it was “unable to assess the safety of silver hydrosols for nutritional purposes as a source of silver in food supplements and the bioavailability of silver from this source.”

Insufficient data

The ANS said the data provided by the petitioner are insufficient to adequately characterise silver hydrosol for risk assessment.”

It added data on ionic silver submiited was not applicable and the toxicological data was insufficient “to allow hazard characterization of silver hydrosol.”

The petitioner in question and leading silver hydrosol supplier, UK-based Natural-Immunogenics, responded to the opinion by saying it will meet EFSA’s requirements to allow its nano-silver products, Sovereign Silver and Argentyn23, to remain on-market before the deadline in 12 months time.

They are currently available under national derogation, as are many other nutrients that are still having their safety and efficacy assessed under the FSD process.

Let’s get clinical

Natural-Immunogenics said human clinical trials would be conducted in the US by a “well-respected, independent clinical research organisation”​ that would provide bioavailability data in the second quarter of 2009.

Silver hydrocols are permitted in the US market, where Natural-Immunogenics has been present for nine years. No adverse events have been reported in that time, the company said.

“Although case studies exist proving the efficacy and safety of silver hydrosols, as manufactured and presented to EFSA by Natural-Immunogenics, none so far provide the bioavailability data EFSA is seeking,”​ said Natural-Immunogenics vice president for education, Robert S. Bell.

“Silver hydrosols provide a safe alternative for immune support at a time when that support is more urgently needed than at any other time in world history.”

The opinion

In its report entitled Risks Arising fromNanoscience and Nanotechnologies on Food and Feed safety and the Environment,​ ANS noted that Natural-Immunogenics referred to​silver hydrosol as “an aqueous colloidal suspension of particles of silver with an average size of 0.8 nm at a concentration of 10 mg/kg or 23 mg/kg in purified water.”

It said the petition failed to present data “on the bioavailability of silver from silver hydrosol, toxicokinetics and repeated-dose toxicity of silver hydrosol.”


The ANS also published guidelines about broader principles to consider when undertaking nanomaterial asessment:

• The currently used risk assessment paradigm (hazard identification, hazard characterisation, exposure assessment and risk characterisation) is considered applicable for nanomaterials. Conventional toxicological testing methods should be used as a starting point to identify hazards from nanomaterials. However, additional issues specific for the properties of nanomaterials must also be considered.

• The risk assessment of nanomaterials must be performed on a case-by-case basis as there are insufficient data to allow generic approaches for their risk assessment.

• The risk assessment of nanomaterials needs to include both nanospecific properties and those common to the equivalent non-nanoforms.

• Due to their physicochemical properties the toxicokinetic and toxicity profiles of nanomaterials cannot be inferred from data on their equivalent non-nanoforms.

Related topics: Regulation & Policy, Suppliers, Supplements

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