Do Nanoparticles Affect Digestion?

Nanoparticles are routinely added to food products and used in food packaging, but the impact they might have on health is still not well understood. Now, a new study from New York researchers suggests that these particles may have more impact on human physiology than previously thought—if humans process them in a similar way to chickens.

Researchers led by Michael Shuler, PhD, a professor of chemical engineering and chair of biomedical engineering at Cornell University in Ithaca, examined how polystyrene nanoparticles, a common, FDA-approved substance (although not one found in food), affected chickens’ absorption of iron.

Short-term exposure initially blocked iron absorption, but the chickens appeared to compensate after longer-term exposure with changes in intestinal cell structure that increased iron absorption.

This isn’t necessarily bad, pointed out Gretchen Mahler, PhD, assistant professor in the department of bioengineering in the Thomas J. Watson School of Engineering and Applied Science at Binghamton University in Binghamton, N.Y., and a co-investigator on the study. “We can’t call the biological response to nanoparticles harmful. Really, the intestinal remodeling shows that the body can respond to and compensate for the exposure. The response could cause harm, for example, by causing a medication to be absorbed in an unexpected way, but we didn’t test that. The point we want to drive home is that exposure to nanoparticles, even nanoparticles that are considered safe, has unexpected physiological consequences.”

Why chickens? “The chicken model is fast-growing, sensitive to micronutrient deficiencies, and relatively inexpensive to work with,” Dr. Mahler explained. “We have shown that the iron bioavailability data collected in chickens correlates well with human studies. Most importantly, chickens are bigger than rats. The intestinal loop surgery that we perform on the chickens to measure iron transport would be very difficult in a smaller animal.”

Next, the Cornell team plans to use its cell culture model to screen for other nanoparticles that may have an effect on nutrient absorption. The in vitro results will direct further in vivo experiments in the chicken model. “We are interested in other nutrients like zinc, copper, and calcium and fat-soluble vitamins like A, D, E, and K,” said Dr. Mahler.

“We think that this study shows that this is an important area that deserves more attention and work. Safety studies should involve chronic exposure results and should look at the more subtle, sublethal effects of nanoparticle consumption,” Dr. Mahler suggested.

The results were reported online Feb. 12 in the journal Nature Nanotechnology.

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