US researchers have studied the concentration of zinc oxide nanoparticles in canned foods and their effects on health. They found that the the zinc contained in canned foods decreases the absorption of nutrients by the intestine.
Canned foods contain zinc oxide in the form of nanoparticles. It is used for its antimicrobial properties and to prevent the staining of sulfur-producing foods. However no study had so been conducted on the amount of nanoparticles that is found in the food and if their presence has an effect on our health.
To bring light on the issue, researchers at the University of Binghamton therefore wanted to dig a little deeper. They found that these nanoparticles have consequences on out digestive system. The results of their work appeared in the journal Food and Function.
At first, the researchers wanted to know the concentration of zinc oxide in canned foods such as tuna, corn or asparagus. They found that canned foods can have up to 100 times the daily dietary zinc intake.
In order to observe the effects on the digestive tract, the scientists put a small intestine model in a cell culture. The cells were then exposed to realistic doses of zinc oxide nanoparticles and subjected to digestion simulation. The goal was to observe the transformation that these nanoparticles could undergo during digestion.
The researchers discovered that zinc oxide can alter how the intestine absorbs nutrients, as well as the expression of intestinal genes and proteins. Indeed, the nanoparticles tend to attach themselves to the intestinal wall and can cause remodeling or loss of microvilli — fine cellular extensions of cylindrical shape about 1 to 2 micrometers in length that can increase absorption. This loss of surface can lead to a decrease in nutrient absorption.
The nanoparticles, in high doses, could also increase the permeability of the intestine, by passing in the blood compounds which should not be found there.
The long-term consequences have not yet been studied. After these first observations on cell cultures, researchers are now studying the effects of these nanoparticles on an animal model.