HomeArticlesInside Our Food You might not have heard of titanium dioxide, but you’ve probably eaten it – it’s a common additive that’s used as a white food colouring in many products like cakes or popular pastries. But there is now a growing evidence base suggesting that titanium dioxide in food could be harmful to our health. What is titanium dioxide (E171)?Titanium dioxide (TiO2) is a white pigment used in many products, from paint to plastics to toothpaste - and it’s also widely used in food. When used as a food additive it’s known as E171 and is typically found in the greatest amounts in processed foods like chocolate, sweets, baked goods, and chewing gum.1 Why is titanium dioxide used in food?Titanium dioxide is one of the most commonly used food additives, thanks to a range of effects. It can be used to make food look brighter or more opaque (thanks to its whitening effect), to give foods like chocolate a smoother texture, and as an anti-caking agent to stop foods like powdered coffee creamer from becoming lumpy.2 Titanium dioxide also shows promise as an additive in food packaging because it can help prolong the shelf-life of fruits such as tomatoes and help ward off bacteria.3,4The use of titanium dioxide in food has been widespread for decades, but in 2019 the Agency for Food, Environmental and Occupational Health & Safety (ANSES) in France concluded that there was not enough evidence to show titanium dioxide was safe to eat. This led the French government to announce it would ban titanium dioxide in food from 2020 onwards.5 In May 2021, the European Food Safety Authority issued a scientific opinion concluding that E171 cannot be ruled out as a cause of cancer, and the European Union is now proposing a ban on the additive.21 But for now, titanium dioxide remains a permitted food additive in most of the EU - so what do we know about its safety?6 Is titanium dioxide safe to eat?There is a growing body of scientific evidence suggesting titanium dioxide may be harmful to health. However, much of this research relates to the risks of inhaling the additive as dust, though the number of studies exploring the risks of eating titanium dioxide is now rising. Research in mice has shown that titanium dioxide consumption can affect the gut, causing changes to microbiota and inflammation, which could, in turn, lead to an increased risk of colorectal cancer and inflammatory bowel disease.7,8 In-vitro studies have suggested that titanium dioxide could cause similar changes elsewhere too, through a process called “oxidative stress”, which results in inflammation and damage to cells and DNA.9 Oxidative stress is thought to contribute to many long-term health conditions, including cancer, diabetes, and cardiovascular diseases.10But titanium dioxide is only a food additive, not a main ingredient, so we tend to eat it in small amounts. In such low quantities, could it really be harmful? That depends on how big each particle of titanium dioxide is, and whether those particles are broken down inside our guts or can reach other parts of our bodies and build up over time.Titanium dioxide nanoparticles pose a greater riskResearchers at the Netherland’s National Institute for Public Health and the Environment (RIVM) detected particles of titanium dioxide in the liver and spleen of humans, with one-quarter of those detected being nanoparticles.11 The proportion of nanoparticles is important, because they behave differently to bigger particles with the same chemical structure, and so can pose a risk to health in smaller amounts.12Is titanium dioxide (E171) made of nanoparticles?In order to scatter light effectively and alter the appearance of food, particles of titanium dioxide (E171) are mostly 200 to 300nm in diameter when used as a food additive– which is too big to be considered a nanoparticle.12 But the process used to make titanium dioxide powder means some of the particles produced are much smaller than this: one study found that 36% of particles in food-grade titanium dioxide were less than 100nm in at least one dimension, making them nano-sized - and therefore potentially more dangerous.13 Titanium dioxide may build up in our bodies over timeThere is also evidence from mice suggesting that titanium dioxide could build up in our bodies over time.14 This accumulation could mean that even if only present in food in small amounts, regularly eating food containing titanium dioxide could have detrimental effects on health over a lifetime.15We have only been adding titanium dioxide to food for several decades – rather than centuries or longer – so researchers do not have long-term data on its accumulation and potential health effects in humans. The long-term safety concerns of accumulated titanium dioxide are particularly relevant for children though, who tend to consume higher amounts of titanium dioxide than adults relative to their body size.15 Does titanium dioxide put food producers and workers at risk? Though it is widely used in food, the main body of research around titanium dioxide is actually on the risks of breathing it in rather than eating it. When inhaled, titanium dioxide dust is listed as a Group 2B carcinogen by the UN’s International Agency for Research on Cancer (IARC).16 That classification means there is some evidence it could cause cancer in humans, but more research is needed for a clearer picture. When it comes to the food you eat, you’re unlikely to inhale much titanium dioxide - for example, while eating a powdered doughnut. But a worker on a production line making thousands of doughnuts every day could be exposed to a lot more. It is the increase in cancers seen during various animal studies that led to the IARC classifying titanium dioxide as a possible carcinogen in humans.17 For example, one study found rats that inhaled large amounts of titanium dioxide particles over two years developed lung tumours.18 But the results of research into workers in the titanium dioxide production industry itself are mixed: the largest study, including workers from six European countries, found a small but significant increase in the risk of lung cancer in workers who were regularly exposed to titanium dioxide dust compared to the general population, but other similar studies in the US and Canada have not found an increase.17 Are there alternatives to using titanium dioxide in food?While the evidence of harm caused by titanium dioxide is far from conclusive, given the concerns raised so far it is worth considering whether other additives could do the same job. Silicon dioxide, also known as silica, or calcium carbonate are two existing food additives that could replace titanium dioxide as a white colourant for food – though there have been concerns raised about the levels of nanoparticles in these additives, too.19 Also, according to an industry group, they would be up to five times less effective than titanium dioxide – meaning we would need to add more of them to achieve the same effect, potentially increasing any associated health risks.2In some cases, titanium dioxide could simply be removed from foods and not replaced. In the US in 2015, for example, Dunkin Donuts removed titanium dioxide from their powdered sugar coating and did not add another whitener.20 While more research is needed into whether titanium dioxide in food is actually damaging to our health or not, perhaps this cautious approach is the best one for the time being: to remove it from foods where we can live without it. How do you feel about eating titanium dioxide in food? Let us know in the comments below!