BY Jimmy Downs

Tuesday May 14, 2013 (foodconsumer.org) -- You may mistakenly believe that all ingredients used in foods, dietary supplements and cosmetics are safe.  Not necessarily.  Evidence shows that nanoparticles used either as a filer, a flow agent (silicon dioxide or titanium dioxide) or a nutrient (zinc oxide) in a processed food or dietary supplements like multivitamins or as a functional agent such as zinc oxide in sunscreens are actually toxic.

A study led by Baoshan Xing from University of Massachusetts in Amherst, MA and colleagues and released in the journal Environmental Pollution tested nanoparticles, aluminum oxide, silicon dioxide, titanium dioxide, and zinc oxide in bacterial cultures including Bacillus subtilis, E. coli and Pseudomona fluorescens for their toxicity, in comparison with micro-scaled counterparts.

All nanoparticles but titanium dioxide are much more toxic than their micro-scaled counterparts.  The researchers found ZnO (zinc oxide, which is commonly used in dietary supplements as the source of zinc, which in itself is an important metal element,) was particularly toxic.  Zinc oxide solutions caused 100% mortality to all three tested bacteria, that is, bacteria can't survive in a zinc oxide solution.   Bacteria are single cells and they die because nanoparticles enter their cells and kill them.

The study revealed that the toxicity of released metal ions like zinc ion was different from that of the oxide particles.  The study shows that nanoparticles attached and killed the bacteria.  These toxic nanoparticles do not have to enter the bacteria to kill them even though it has been demonstrated in many studies that nanoparticles are insoluble and they are small enough to be able to enter cells freely to disrupt DNA and other molecules killing cells or causing injury to cells.

Other nanoparticles are less toxic than zinc oxide, according to the study report.  The researchers reported "Al2O3 (aluminum oxides) nanoparticles had a mortality rate of 57% to B. subtilis, 36% to E. coli, and 70% to P. fuorescens.  SiO2 (silicon dioxide) nanoparticles killed 40% of B. subtilis, 58% of E. coli, and 70% of P. fluorescens." which are still substantial. 

Both zinc oxide and silicon dioxide in addition to titanium dioxide are commonly used in dietary supplements like multivitamins.  Some dietary supplement manufacturers have stopped using titanium dioxide, but are still using other nanoparticles such as zinc oxide and silica (silicon dioxide).

Microparticles can too damage or kill cells although they are less toxic than their nano-scaled counterparts.