A first-of-its-kind study has found that tinned goods like tuna, chicken, corn and asparagus can significantly exceed the recommended daily intake of zinc.
The mineral – which plays an important role in many of the human body's essential functions – is often used to line the inside of cans thanks to its antimicrobial qualities. Researchers from Binghamton University tested foods naturally low in zinc to see how the packaging affected the product.
"It was found the zinc present in a serving of these foods is approximately one hundred times higher than the recommended dietary allowance,” study co-author Professor Gretchen Mahler said in a statement.
An in vitro model of a human’s small intestine was then used to investigate the effects this zinc oxide nanoparticle exposure might have on the body.
"We found zinc oxide nanoparticles at doses that are relevant to what you might normally eat in a meal or a day can change the way your intestine absorbs nutrients or your intestinal cell gene and protein expression,” Professor Mahler said.
Exposure to zinc oxide nanoparticles altered the cells representing the gastrointestinal tract, reducing the surface area available for nutrient absorption. It was also found to cause inflammation, which makes the digestive tract more permeable or penetrable.
“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.”
But don’t bin the tins just yet – Mahler says that the long-term effects of nanoparticle ingestion are on human health are still unknown and the findings of the in vitro study will need to be replicated in animals trials.
“What I can say is that our model shows that the nanoparticles do have effects on our in vitro model, and that understanding how they affect gut function is an important area of study for consumer safety.”