In an article published on April 9, 2018, news provider ScienceDaily informed about a new study investigating the effects of ingested zinc oxide (ZnO) nanoparticles on the digestive tract. The study was first published on February 20, 2018 in the peer-reviewed journal Food & Function and conducted by Fabiola Moreno-Olivas and colleagues from Binghamton University, U.S., and the U.S. Department of Agriculture.
ZnO nanoparticles are used in the coating of cans for certain foods due to their antimicrobial properties and to prevent staining of sulfur-producing foods. The researchers used mass spectrometry to estimate the migration of ZnO nanoparticles in canned corn, tuna, asparagus, and chicken. The levels found in the food were 100 times higher than the daily dietary allowance of zinc. The researchers then tested the effect of the determined ZnO levels on intestinal cells. They found that ZnO nanoparticles “tend to settle onto the cells representing the gastrointestinal tract and cause remodeling or loss of the microvilli, which are tiny projections on the surface of the intestinal absorptive cells that help to increase the surface area available for absorption,” Gretchen Mahler, the study’s senior author, explained. Loss of surface area can lead to decreased nutrient absorption. Further, Mahler and colleagues observed decreases in iron and glucose transport consistent with observed changes in gene expression for their transporters.
The researchers are now also studying the effects of ZnO nanoparticle ingestion in an animal model with chickens. “We have seen that our cell culture results are similar to results found in animals and that the gut microbial populations are affected,” Mahler noted. She concluded that “understanding how [nanoparticles] affect gut function is an important area of study for consumer safety.”
Update 1:
On April 20, 2018, this article was retracted by the senior author Gretchen Mahler due to “a mistake . . . in the calculations,” that made “the reported findings presented on the zinc (Zn) coming from food . . . unreliable.” The senior author emphasized that this was “a result of honest errors made in the data analysis,” more specifically, a “unit error . . . [in] the calculations that converted the concentration of zinc in our small samples to a serving size that would be ingested.” Therefore, the author stated, “the claim in the article that Zn coming from canned food exceeded the recommended dietary allowance is no longer supported” and “it is now believed that the levels of predicted Zn coming from canned food are withing the recommended dietary allowance.” The retraction followed the publication of a critical article by the UK’s “biggest health website” NHS, on April 13, 2018. This article pointed to an error in the authors’ calculations and instead “calculated this meal should have contained 2.1 mg of zinc, not 996 mg,” as originally reported by the authors. The NHS further informed that “the recommended daily allowance is about 9.5 mg a day for men and 7 mg for women,” therefore “this [(2.1 mg zinc per portion)] would be within the limit.”
Update 2:
The corrected research article, largely based on the results repoted in the retracted manuscript, was published on November 29, 2018, in the peer-reviewed journal Food and Chemical Toxicology. The overall conclusions of the study remained largely unchanged. The authors summarized that “a physiologically relevant dose” of ZnO nanoparticles “can cause a significant decrease in glucose transport, which is consistent with gene expression changes for the basolateral glucose transproter GLUT2.” Further, there is “evidence” that the ZnO nanoparticles “affect the microvilli of the intestinal cells, therefore reducing the amount of surface area available to absorb nutrients.” Their study characterized “nutrient absorption in an in vitro model of the human small intestine” and may serve as a first step to evaluate “the cytotoxicity of nanoparticles in food packaging” with regard to “consumer safety,” the authors concluded.
Read more
Binghamton University (April 9, 2018). “Food packaging could be negatively affecting nutrient absorption in your body.” ScienceDaily
Bazian (April 13, 2018). “Media reports about high levels of zinc in tinned tuna are based on flawed data.” NHS
Retraction Watch (April 2018). “That study reporting worrisome levels of zinc in tuna? It’s being retracted.”
Will Chu (May 2, 2018). “Gut health study recalled after zinc levels in tuna miscalculated.” NutraIngredients
References
Moreno-Olivas, F., et al. (2018). “ZnO nanoparticles affect intestinal function in an in vitro model.” Food & Function 9:1475-1491.
Moreno-Olivas, F., et al. (2018). “Retraction: ZnO nanoparticles affect intestinal function in an in vitro model.” Food & Function 9:1475-1491.
Moreno-Olivas, F., et al. (2018). “ZnO nanoparticles affect nutrient transport in an in vitro model of the small intestine.” Food and Chemical Toxicology 124: 112-127.
