Titanium dioxide (E171), the enemy dye of the gut


Titanium dioxide promotes inflammatory bowel disease. The evidence emerges from new research at the University of Zurich. As a result of which people with inflammatory bowel disease are urged to
avoid foods that contain it

Titanium dioxide, a white dye

Titanium dioxide is a white pigment of mineral origin widely used in food as a coloring agent (E171). It is found in candies, chewing gum, marshmallows, sauces, confectionery, baked goods, and cheese products. It is also widely used in medicines and toothpastes as well as in cosmetics and sunscreens.

Nanometer particles

What makes this additive hazardous to health is the nanometer form in which it is produced; in fact, it can contain up to 3.2 percent by weight in nanoparticles, less than 100 nanometers in size. That is, millionths of a millimeter, so microscopic that they pass through cell walls.

Severe risks to the gut

According to the study, led by Gerhard Rogler, professor of Gastroenterology and Hepatology at the University of Zurich,‘titanium dioxide nanoparticles penetrate human intestinal epithelial cells.’ They are perceived as danger signals and trigger inflammatory processes. (1)

Particles absorbed with food

The study also verified that people with ulcerative colitis have a higher concentration of titanium dioxide in their blood. ‘This shows that these particles can be absorbed from food under certain disease conditions,’ Rogler explains.

From in vitro to in vivo

In addition to the in vitro experiment, conducted on cell cultures, the Zurich team investigated the effects of titanium dioxide ingestion in vivo, on mice, used for research on inflammatory bowel disease. When orally administered the nanoparticles to mice, severe intestinal inflammation and increased damage to the guinea pigs’ intestinal mucosa was detected.

From the gut to the reproductive system

The relationship between the ingestion of titanium dioxide and the occurrence of intestinal diseases has been demonstrated many times by the scientific community. (2) More entrenched is the evidence of damage to the reproductive system.

In Italy, 4 years ago, a study conducted by theIstituto Superiore di Sanità showed damage on the reproductive, endocrine and immune systems of rats, particularly in that of females. Administration of small doses of titanium dioxide for 5 days-a dose comparable to human consumption of the dye-produced altered ovarian tissue and testosterone metabolism in guinea pigs. (3)

Many suspicions, no precautions

Despite the evidence, health institutions have not taken any precautions or dictated restrictions on the use of E171 in food. The European Food Safety Authority (Efsa) reviewed its risk profile in 2016, concluding that there is a lack of obvious adverse effects related to oral consumption.

The Authority has not set any employment limits. But he stressed the need for new research, to test potential effects on the reproductive system. (4) A review to be carried out urgently, in our opinion, also in light of the new research criteria for nanoparticles. (5)

Titanium dioxide, how to recognize it

The presence of Titanium Dioxide in products-food and non-food-is indicated on the label.

When it is added into foods it is indicated on the label by its name, which is E171.

In cosmetics and sunscreens, where it is used for its absorbent properties or as a sunscreen, it is referred to in the Inci (the list of ingredients in cosmetics) as titanium dioxide or by the abbreviation C.I. 77891, when used as a coloring agent.

Marta Strinati


(1) The study Titanium dioxide nanoparticles exacerbate DSS-induced colitis: role of the NLRP3 inflammasome. Gut conducted by the team of Swiss researchers led by Gerhard Rogler, professor of gastroenterology and hepatology at the University of Zurich, was presented on July 19, 2017. http://www.media.uzh.ch/en/Press-Releases/2017/titanium-dioxide-nanoparticles-colitis.html

(2) Among the latest scientific works on the topic is the study published in January 2017 by INRA, Institut National de la Recherche Agronomique http://presse.inra.fr/en/Press-releases/Food-additive-E171

(3) The study was published in July 2013 in Nanotoxicology Early Online. http://www.tandfonline.com/doi/abs/10.3109/17435390.2013.822114

(4) Efsa opinion on titanium dioxide as a food additive was published on June 28, 2016


(5) On the Efsa position on the safety of titanium dioxide, Francesco Cubadda, researcher at the Istituto superiore di sanità (Iss) and expert in Toxicology and nanomaterials, told The Food Fact in January 2017. that when that opinion was prepared there was still not much evidence of damage to the intestinal system and there was a lack of updated guidelines.

Marta Strinati

Professional journalist since January 1995, he has worked for newspapers (Il Messaggero, Paese Sera, La Stampa) and periodicals (NumeroUno, Il Salvagente). She is the author of journalistic surveys on food, she has published the book "Reading labels to know what we eat".