The tiniest particles of titanium dioxide—commonly used to make candies, cookies, and other ultra-processed foods look brighter and more visually appealing, especially to kids—can raise blood sugar levels and impair how the body processes glucose, among other health harms, according to new research in mice. 

The study, published this month [May 2025] in Food and Chemical Toxicology, adds to growing concerns over the safety of titanium dioxide (TiO₂), a widely used color additive that is banned in the EU but widely used in the U.S. and elsewhere. It also highlights the food industry’s increasing use of microscopic materials to preserve or enhance foods.  

“These findings raise important questions about the potential risks of titanium dioxide nanoparticles in food products, particularly in relation to metabolic disorders such as obesity and type 2 diabetes,” the researchers say.

The findings come several months after the FDA banned a coloring agent called Red Dye No. 3 amid several efforts nationwide to ban food chemicals, particularly from public school meals. The U.S. Department of Health and Human Services (HHS) has also said that it will direct food manufacturers to phase out eight petroleum-based food dyes found in hundreds of foods.

Titanium dioxide nanoparticles (TiO₂ NPs) are ultrafine particles between one and 100 nanometers. By comparison, a sheet of paper is about 1,000 nanometers thick. Unlike larger TiO₂ microparticles, nanoparticles may act as intestinal endocrine disruptors, the researchers suggest. 

The nanoparticles appear to interfere with how the gut senses nutrients from food in the body, and how it produces and releases key hormones involved in digestion and blood sugar level control (glucose homeostasis). When the body can’t control blood sugar properly, it can lead to type 2 diabetes and obesity by making it harder to use insulin and easier to store fat.

TiO₂ nanoparticles in mice caused a weakened hormone response to food-related signals, the study shows. It also led to:

• Disrupted blood glucose regulation: Mice fed food containing 1% titanium dioxide nanoparticles had much higher blood sugar levels and more signs of poor blood sugar control compared to those fed larger particles with 1% TiO₂ and others fed no titanium dioxide at all.
• Intestinal changes: Nanoparticles significantly altered how the intestinal lining developed—without visibly damaging tissue or slowing cell growth.
• Reduced levels of gut hormones, including GLP-1 (regulates blood sugar), PYY (promotes fullness), and cholecystokinin, or CCK (aids digestion).
• Significant drop in enteroendocrine cells, leading to problems with how the gut releases intestinal hormones like GLP-1, which can increase the risk of obesity, type 2 diabetes, and other symptoms of metabolic syndrome.

Widespread use of titanium dioxide despite health concerns

Used widely in ultra-processed foods (UPFs), particularly those marketed to children, titanium dioxide is a whitening pigment that does not offer any nutritional or preservative benefit—only cosmetic. Popular products containing titanium dioxide (labeled E171) include Skittles, Starbursts, Trident White peppermint gum, Duncan Hines Creamy Vanilla Frosting, and cookies like Nabisco Chips Ahoy!  

Despite its prevalence, titanium dioxide has been linked to multiple severe adverse health outcomes, mainly studied in animal and cell models. These include:

• DNA damage, with the potential to cause cancer
• Intestinal inflammation
• Obesity-related metabolic disorders
• Possible impacts on neurodegenerative diseases such as Alzheimer’s disease

The  International Agency for Research on Cancer (IARC) classifies titanium dioxide as “possibly carcinogenic to humans” based on animal studies. In 2021, the European Food Safety Authority (EFSA) concluded that it could no longer consider titanium dioxide safe for use in food. France banned the additive in 2020, followed by the European Union in 2022.

However, it is still permitted for use in foods in the U.S., where it can appear on ingredient labels as “artificial color” or “colored with titanium dioxide,” though labeling is not always required. The FDA currently classifies titanium dioxide as a food additive as GRAS, or “generally recognized as safe,” though it allows no more than 1% by weight in food. Its particle size is not regulated.

New York lawmakers introduced proposed legislation earlier this year [March 2025] to ban titanium dioxide along with six other substances from food manufactured, distributed, or sold in the state. Another bill would require companies to disclose when they add chemicals to food and drinks determined as GRAS.   

Nanoparticles may be more harmful than larger particles

In the new study, the researchers studied five-week-old male mice over the course of 12 weeks to examine how the size of titanium dioxide (TiO₂) particles influences health outcomes, particularly their effect on gut hormones and blood sugar.

They used the FDA-permitted maximum TiO₂ content of 1% in food products. Each animal’s body weight and blood glucose levels were monitored weekly, and food intake was tracked daily during the final week. The researchers then conducted experiments on lab-grown intestinal organoids—miniature, three-dimensional models of the human gut developed from stem cells.

The findings reinforce earlier studies suggesting that TiO₂ nanoparticles may pose different—and in some instances, greater—health risks than microparticles. MPs are roughly up to 10 times larger but still only about the size of a fine grain of sand.

Because of their extremely small size, nanoparticles have a large surface area-to-volume ratio, which means they break down or dissolve faster, and can more easily penetrate cells and tissues. They also tend to linger in the body longer, which may explain their stronger potential to disrupt normal biological functions, the researchers note.

The 12-week intervention was long enough to detect short-term metabolic disruptions, researchers say, but more studies are needed to examine the long-term effects. Future studies could determine whether the body’s hormonal and metabolic systems return to normal once titanium dioxide nanoparticles are removed from the diet, they say.

To reduce your exposure to titanium dioxide (TiO₂) in food, read ingredient labels carefully, limit ultra-processed foods, and buy organic foods.

Reference

Zou K, Du L, Qin J, et al. Titanium dioxide nanoparticles disturb glucose homeostasis in association with impaired enteroendocrine cell differentiation. Food Chem Toxicol. Published online May 1, 2025. doi:10.1016/j.fct.2025.115504