If you’re in the habit of reading food labels, you’ll often come across ingredients you can’t pronounce. Tertiary butylhydroquinone, or TBHQ, might be one of them.

TBHQ is an additive to preserve processed foods. It acts as an antioxidant, but unlike the healthy antioxidants you find in fruits and vegetables, this antioxidant has a controversial reputation.

TBHQ, like many food additives, is used to extend shelf life and prevent rancidity. It’s a light-colored crystalline product with a slight odor. Because it’s an antioxidant, TBHQ protects foods with iron from discoloration, which food manufacturers find beneficial.

It’s often used with other additives like propyl gallate, butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT). BHA and TBHQ are usually discussed together, as the chemicals are closely related: TBHQ forms when the body metabolizes BHA.

TBHQ is used in fats, including vegetable oils and animal fats. Many processed foods contain some fats, so it’s found in a wide range of products — for example, snack crackers, noodles, and fast and frozen foods. It’s allowed to be used in the highest concentrations in frozen fish products.

But food isn’t the only place you’ll find TBHQ. It’s also included in paints, varnishes, and skin care products.

The Food and Drug Administration (FDA) determines which food additives are safe for U.S. consumers. The FDA puts a limit on how much of a particular additive can be used:

  • when there’s evidence that large quantities may be harmful
  • if there is a lack of safety evidence overall

TBHQ can’t account for more than 0.02 percent of the oils in a food because the FDA doesn’t have evidence that greater amounts are safe. While that doesn’t mean more than 0.02 percent is dangerous, it does indicate that higher safety levels haven’t been determined.

So what are the potential dangers of this common food additive? Research has linked TBHQ and BHA to numerous possible health problems.

According to the Centers for Science in the Public Interest (CSPI), a well-designed government study found that this additive increased the incidence of tumors in rats.

And according to the National Library of Medicine (NLM), cases of vision disturbances have been reported when humans consume TBHQ. This organization also cites studies that have found TBHQ to cause liver enlargement, neurotoxic effects, convulsions, and paralysis in laboratory animals.

Some believe BHA and TBHQ also affect human behavior. It’s this belief that has landed the ingredients on the “do not consume” list of the Feingold Diet, a dietary approach to managing attention deficit hyperactivity disorder (ADHD). Advocates of this diet say that those who struggle with their behavior should avoid TBHQ.

As noted above, the FDA considers TBHQ to be safe, particularly in small amounts. However, some research indicates that Americans may be getting more than they should.

A 1999 evaluation by the World Health Organization found the “average” intake of TBHQ in the United States to be around 0.62 mg/kg of body weight. That’s about 90 percent of the acceptable daily intake. Consumption of TBHQ was at 1.2 mg/kg of body weight in those who eat high fat diets. That results in 180 percent of the acceptable daily intake.

The authors of the evaluation did note that several factors led to an overestimation in the reporting, thus it’s difficult to be certain of the actual “average” TBHQ intake.

Whether you manage the diet of a child with ADHD or are just concerned about eating a preservative tied to possible health risks, getting into the habit of reading labels can help you avoid TBHQ and related preservatives.

Watch for labels that list the following:

  • tert-butylhydroquinone
  • tertiary butylhydroquinone
  • TBHQ
  • butylated hydroxyanisol

TBHQ, like many questionable food preservatives, is found in processed foods meant to withstand a long shelf life. Avoiding these packaged foods and opting for fresh ingredients is a surefire way to limit it in your diet.