'Food packaging may negatively affect digestion'

Food packaging could be negatively affecting the way in which your digestive tract operates, according to a study.

"We found that zinc oxide (ZnO) nanoparticles at doses that are relevant to what you might normally eat in a meal or a day can change the way that your intestine absorbs nutrients or your intestinal cell gene and protein expression," said Gretchen Mahler, an associate professor at Binghamton University in the US.

These ZnO nanoparticles are present in the lining of certain canned goods for their antimicrobial properties and to prevent staining of sulphur-producing foods, Mahler said.

Canned corn, tuna, asparagus and chicken were studied using mass spectrometry to estimate how many particles might be transferred to the food.

The study published in the journal Food & Function found that the food contained 100 times the daily dietary allowance of zinc.

Mahler then looked at the effect the particles had on the digestive tract.

"People have looked at the effects of nanoparticles on intestinal cells before, but they tend to work with really high doses and look for obvious toxicity, like cell death," said Mahler.

"We are looking at cell function, which is a much more subtle effect, and looking at nanoparticle doses that are closer to what you might really be exposed to," Mahler said.

"They tend to settle onto the cells representing the gastrointestinal tract and cause remodelling 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," said Mahler.

This loss of surface area tends to result in a decrease in nutrient absorption.

Some of the nanoparticles also cause pro-inflammatory signalling at high doses, and this can increase the permeability of the intestinal model.

"An increase in intestinal permeability is not a good thing - it means that compounds that are not supposed to pass through into the bloodstream might be able to," said Mahler.