Butylated hydroxytoluene

BHT (butylated hydroxytoluene) is a synthetic antioxidant added to foods to prevent fats and oils from spoiling. Fast-food suppliers may use BHT to help keep frying oils, packaged snacks, or dried potato products fresh during storage. Regulatory agencies allow only small amounts of BHT, but it remains controversial. Studies in lab animals have shown that high doses can affect the endocrine system and potentially promote tumors. Some countries have responded by removing or banning BHT in foods as a precaution, even though typical human exposure is much lower than those test levels.

Aliases / Common Names: BHT; E321; 2,6-di-tert-butyl-4-methylphenol; di-tert-butyl-p-cresol Regulatory Status & Exposure: In the U.S., BHT is an approved food additive used as an antioxidant in specific fatty foods (e.g. up to 0.02% of certain oils or about 50 ppm in dry goods like cereal). The FDA removed BHT from its old GRAS list in the 1970s and instead set concentration limits by regulation. Joint FAO/WHO experts (JECFA) established an acceptable daily intake (ADI) of 0.3 mg per kg body weight, and the European Food Safety Authority set a similar ADI of 0.25 mg/kg in 2012. Estimated intakes for most consumers are well below these limits. However, at the highest consumption levels (e.g. children who eat a lot of BHT-preserved foods), exposure can reach or even exceed the ADI in some cases. Internationally, oversight varies. The European Union has taken a precautionary approach – BHT is not allowed in foods for infants and young children, and as of 2025 the EU is moving toward banning BHT in most foods altogether. Japan and several other countries likewise restrict synthetic antioxidants in favor of natural alternatives. In California, unlike BHA, BHT is not currently on the Proposition 65 carcinogen list (reflecting its less conclusive cancer evidence). U.S. regulators are re-examining BHT’s safety in light of new data, but for now it remains legal in foods at low levels. Technical Evidence: Mechanistically, BHT’s antioxidant action stems from its phenolic structure, which scavenges free radicals to delay rancidity. Paradoxically, the same reactivity can yield potentially harmful metabolites. In rodents, BHT at high doses induces liver enzymes and oxidative stress, leading to thyroid hormone imbalances and liver enlargement. Two-generation rat studies found that very high dietary BHT (hundreds of mg/kg) reduced litter size and pup growth and increased liver tumor incidence, although only at doses far above typical human intake. Notably, BHT alone has shown limited carcinogenicity in standard animal tests – one reason the International Agency for Research on Cancer classifies it as Group 3 (“not classifiable as to human carcinogenicity”). Some research even suggests BHT might have anti-carcinogenic effects under certain conditions by counteracting more potent carcinogens at low doses. However, other experiments indicate BHT can promote tumors initiated by other chemicals, acting as a tumor promoter in the presence of known carcinogens. Likewise, evidence on genotoxicity is mixed: BHT is not strongly DNA-damaging in most standard tests, but it can cause subtle chromosome effects and sperm abnormalities in some laboratory assays. The consensus from regulatory reviews is that BHT is not a definitive carcinogen or mutagen at the low levels people ingest. The primary health concerns instead center on its potential to disrupt endocrine signaling and to cause organ toxicity with high or prolonged exposure. BHT’s metabolites (including a reactive quinone methide) have been implicated in liver toxicity in animals, which in turn can affect thyroid function (since the liver clears thyroid hormones). This cascade may explain thyroid hypertrophy seen in BHT-fed rodents. Importantly, there is a lack of human epidemiological studies directly linking normal BHT consumption to disease. The safety debate therefore relies on animal data and mechanistic insights, with regulators weighing large safety margins between typical human exposure and doses that caused harm in animals. Fast-Food Context: BHT finds its way into fast-food fare primarily through processed ingredients. It may be added to the oils or shortenings used for deep-frying French fries, chicken, and other items, in order to prolong the oil’s shelf life and prevent off-flavors. Fast-food restaurants typically receive pre-formulated frying oil from suppliers, and in the past those oils sometimes contained BHT (or related antioxidants like TBHQ) as preservatives. BHT is also used in dry mixes and packaged foods that fast-food chains use behind the counter. For example, dehydrated potato shreds or flakes (used in forming hash browns or mashed potato sides) can legally contain a small amount of BHT to protect against oxidation. Similarly, some breakfast cereals or seasonings with added fats might come with BHT if the restaurant uses branded pre-packaged portions. Even food packaging can be a source – BHT is used in certain packaging materials (like liners) to prevent oxidation, and it can migrate into the food over time. Overall, the use of BHT in fast-food contexts is about maintaining product consistency and storage life, ensuring that frying oils don’t go rancid and that items taste fresh even if they’re shipped from central kitchens. Modern trends are shifting away from BHT as consumers demand “cleaner” labels, so some chains have announced removal of BHA/BHT from recipes in favor of natural antioxidants. Sensitive Populations / Notes: Young children are a sensitive group for BHT. Because kids consume more food per body weight and may favor BHT-containing snacks, their relative exposure can be higher – in fact, European assessments found that high-end BHT exposure in children could hit levels of concern. This is one reason the EU bans BHT in infant and toddler foods. Pregnant women and infants may also be more susceptible to any endocrine-disrupting effects, since thyroid hormones are crucial for development; agencies recommend prudence with additives that affect thyroid homeostasis. People with existing thyroid disorders (like hypothyroidism) could theoretically be at higher risk from BHT, as their hormonal balance is delicate. Additionally, a subset of individuals may have acute sensitivities or allergies to BHT – reports (including an older FDA petition) note cases of allergic reactions such as hives and asthma in response to BHT-containing foods. These cases are not common, but they highlight that BHT isn’t entirely inert in everyone. Finally, it’s worth noting that BHT is also used in cosmetics and personal care products; someone highly exposed via both diet and cosmetics might accumulate more in their body. BHT is fat-soluble and has been detected in human fat tissue and breast milk, although typically at very low concentrations. These findings reinforce why some consumers choose to avoid BHT – not because everyday use is definitively harmful, but because its necessity is questioned given that alternative, natural preservatives (like vitamin E/tocopherols) can often serve the same role without the lingering questions about long-term health effects.

We assign the high tier using published research, regulatory guidance, and PRūF’s additive taxonomy. Restaurant usage is derived from public ingredient disclosures and mapped to menu items where this additive appears.