Tinned tuna. (Photo: Stock File)
Tinned tuna zinc could harm bowel metabolism
Tuesday, April 17, 2018, 01:00 (GMT + 9)
New research carried out by Binghamton University, New York, suggests that tinned tuna contains up to 100 times more zinc than is safe, which could seriously affect people's bowel nutrient absorption.
Zinc is a type of mineral commonly used to line the inside of cans due to its anti-microbial qualities that can help to prolong foods' shelf lives.
However, study author Professor Gretchen Mahler explains that zinc leaches into food later becomes lodged in people's digestive systems, altering their abilities to absorb nutrients. This issue may also make their guts more permeable, allowing toxic substances to enter their bloodstreams.
The proposed health condition 'leaky gut syndrome', which is not medically recognised, claims disorders such as multiple sclerosis are caused by the immune system reacting to substances absorbed into the bloodstream via a porous bowel. Excessive zinc intake has been linked to seizures, fever, vomiting and fainting.
The researchers analysed cans of sweetcorn, tuna, asparagus and chicken, which were chosen due to them being naturally low in zinc.
Results further suggest tuna tin linings and the fish at the centre of such cans are contaminated with more than 5,000 ppm of zinc. The juices at the bottom of the can have around a third of the metal contamination as the food touching the tin.
A laboratory model of the human small intestine found tiny fragments of zinc cause inflammation, which makes the gut more permeable and allows harmful chemicals to enter the bloodstream.
The study also found the transport of iron and glucose falls by three quarters and almost a third, respectively, after zinc exposure.
According to Mahler, it has been shown that 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.
Some of the nanoparticles also cause pro-inflammatory signalling at high doses and this can increase the permeability of the intestinal model.
Photo Courtesy of FIS Member ANFACO-CECOPESCA - Asociacion Nacional de Fabricantes de Conservas de Pescados y Mariscos-
Professor Mahler stresses, however, the results are based on zinc's effect on cells grown in a laboratory, with long-term human health implications being unclear.
"It is difficult to say what the long-term effects of nanoparticle ingestion are on human health, especially based on results from a cell-culture model," she added.
The research findings was published in the journal Food & Function.