Food Packaging May Impact Nutrient Absorption

 In Naturopathic News

Node Smith, ND

A recent article was published that supports staying away from processed foods – and even canned foods.1 Apparently, a common substance used in the lining of certain canned foods may be negatively affecting the absorption of nutrients in the intestine. The chemical compound may be surprising: Zinc Oxide.

Zinc Oxide (ZnO)

Zinc Oxide (ZnO) is a compound that is well known by anyone who has made their own sunscreen or looked for natural sunscreen alternatives. ZnO is generally considered safe, though the fumes from the powder are known to be toxic, and when making your own sunscreen many recipes will specifically warn not to inhale the dust.

The research done on the toxicity of ZnO looked at large doses

The researchers of this study point out that most of the research done on the toxicity of ZnO has looked at large doses and toxic markers such as cell death. There has been no research analyzing the functional effects of ZnO at a cellular level at doses that are comparable to what might be ingested in a single meal or over the course of a single day. These were the doses and cellular responses that were looked at.

ZnO is used in the lining of cans for its antimicrobial properties

ZnO is used in the lining of cans for its antimicrobial properties, and also to prevent the staining of sulfur-producing foods. The study looked at canned tuna, chicken, asparagus, and corn specifically. Mass spectrometry was used to estimate how much ZnO nanoparticles may be transferred to food. It was found that 100 times the daily allowance for zinc was transferred to the foods from the can’s lining.

Effects of the nanoparticles on the intestinal cells were significant

The effects of the nanoparticles on the intestinal cells were significant. The nanoparticles showed a tendency to settle on cells and cause remodeling or loss of microvilli – the projections which increase cellular surface area for effective absorption. The loss or change in microvilli results in decrease nutrient absorption. It was also noted that some of the nanoparticles also caused pro-inflammatory signalling, which led to an increase in permeability in the intestinal model.

Authors of the study are not commenting on the potential long-term effects of ZnO nanoparticle ingestion

At this point, the authors of the study are not commenting on the potential long-term effects of ZnO nanoparticle ingestion, but further animal studies are being scheduled.


  1. Moreno-olivas F, Tako E, Mahler GJ. ZnO nanoparticles affect intestinal function in an in vitro model. Food Funct. 2018;9(3):1475-1491.
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Node Smith, ND, is a naturopathic physician in Portland, OR and associate editor for NDNR. He has been instrumental in maintaining a firm connection to the philosophy and heritage of naturopathic medicine among the next generation of docs. He helped found the first multi-generational experiential retreat, which brings elders, alumni, and students together for a weekend camp-out where naturopathic medicine and medical philosophy are experienced in nature. Four years ago he helped found the non-profit, Association for Naturopathic ReVitalization (ANR), for which he serves as the board chairman. ANR has a mission to inspire health practitioners to embody the naturopathic principles through experiential education. Node also has a firm belief that the next era of naturopathic medicine will see a resurgence of in-patient facilities which use fasting, earthing, hydrotherapy and homeopathy to bring people back from chronic diseases of modern living; he is involved in numerous conversations and projects to bring about this vision.

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