Aug 4, 2015 (foodconsumer.org) -- Zinc oxide, a type of nanoparticles, is commonly used as a nutrient in dietary supplements and foods, and as a UV shielding agent in sunscreens. A new study finds that zinc oxide like others such as titanium dioxide is both cytotoxic and genotoxic. And zinc oxide is more harmful than titanium dioxide at higher concentrations.
Some dietary supplement manufacturers like vitacost have stopped using titanium dioxide in dietary supplements because of their toxicity. Titanium dioxide and other nanoparticles like silicon dioxide are commonly used as dispersing agents in dietary supplements and foods.
For the study, researchers tested zinc oxide and titanium dioxide at 50, 100, 250 and 500 ppm for the cytotoxicity in human erythrocytes and the genotoxicity in human lymphocytes.
Zinc oxide and titanium dioxide at 250 ppm were found to result in 65% and 53% hemolysis, respectively, indicating both nanoparticles are cytotoxic.
Both nanoparticles also promoted the formation of reactive oxygen species concomitant with depletion of naturally occurring antioxidants glutathione and Glutathione S-transferase (an antioxidant enzyme) levels and increased superoxide dismutase, catalase and lipid peroxidation in a dose-responsive manner. This indicates that the nanoparticles may cause cellular and genetic damage by producing reactive oxygen species and increasing oxidative stress.
The DNA damage induced by zinc oxide and titanium dioxide depended on the concentration of the nanoparticles. High concentrations caused greater DNA damage. Zinc oxide was more genotoxic than titanium dioxide at higher concentrations. (David Liu)
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