Titanium dioxide is a chemically inert substance that has generally been considered harmless to the human body.
Recently, however, titanium dioxide nanoparticles have started to be used more frequently as a white pigment in cosmetics and toiletries (such as toothpaste), some medicines, and food items (including cake icing and marshmallows) as additive E171.
This has led to a more careful scrutiny of its potential impact on health and well-being, with some researchers warning against its possible negative effects.
An elevated concern might arise for patients living with inflammatory bowel disease (IBD), or colitis, which typically takes two forms: Crohn's disease, which is more common in women, and ulcerative colitis, which is more common in men.
Currently, according to the Centers for Disease Control and Prevention (CDC), up to 1.3 million people have been diagnosed with a form of IBD.
Since its causes are still unclear, and a cure has not yet been found, it is crucial for patients to be able to keep their condition under control.
Recently, researchers from the University of Zurich in Switzerland have looked at what happens when the digestive system absorbs nanoparticles of titanium dioxide. Their findings suggest that foods containing titanium dioxide could be particularly harmful for patients with IBD.
This new study, which was led by Dr. Gerhard Rogler, is published in the journal Gut.
Immune system flags up titanium dioxide
The scientists focused their efforts on the NLRP3 inflammasome, which is a protein complex released by the non-specific immune system to flag up potential threats. When activated, the NLRP3 inflammasome triggers inflammation as a way of counteracting the perceived hazard.
In this study, Dr. Rogler and his colleagues first used cell cultures, before moving on to mice to study the effect of titanium dioxide nanoparticles.
When working with cell cultures, the scientists observed that the nanoparticles were able to infiltrate epithelial cells (which form the lining of cavities, blood vessels, and organs), as well as macrophages (which are white blood cells that "eat" dead or foreign cellular tissue in the human body).
In bypassing these cells, titanium dioxide accumulates in the body and is flagged up as a threat by the NLRP3 inflammasomes.
The researchers also noted that patients with forms of IBD absorb a significant amount of titanium dioxide in their bloodstream because their intestinal barrier is damaged.
"This shows that [titanium dioxide] particles can be absorbed from food under certain disease conditions," says Dr. Rogler.
When determining mice to ingest titanium dioxide nanoparticles, the scientists observed once more that the NLRP3 complex was activated, causing severe inflammation of the intestines and damage to the intestinal barrier. Crystals of titanium dioxide also accumulated in the mice's spleens, the researchers noted.
The findings, so far, led Dr. Rogler and his colleagues to suggest that titanium dioxide nanoparticles might be especially harmful to patients diagnosed with a form of IBD.
This being the case, any foods containing such nanoparticles should, in the future, be avoided where the condition is concerned.
"Based on our results, patients with an intestinal barrier dysfunction as found in colitis should abstain from foods containing titanium dioxide," emphasizes Dr. Rogler.
The researchers encourage further studies around this topic, saying that more evidence is needed to consolidate their preliminary results.