If you’re trying to eat healthy, you know to avoid many restaurant meals that are high in fat and sodium. But now a new study has found there’s another potential risk to dining out: hormone-disrupting chemicals called phthalates.

These endocrine-disrupting chemicals are used in many plastic materials and may be migrating to your takeout orders, according to a new study published last week in the peer-reviewed journal Environment International.

Researchers from the University of California at Berkeley, the University of California at San Francisco, and George Washington University found that people who reported eating more meals at fast-food joints, restaurants, and cafeterias had nearly 35 percent higher levels of phthalates in their urine than people who relied mostly on grocery stores for their food.

The new findings indicate that food from restaurants, especially fast food, might be worse for our health than experts previously thought.

“Endocrine-disrupting chemicals have been purported to have caused the obesity epidemic, fertility problems, and a host of other ailments that seem to be increasing with [our consumption of] processed and mass-handled foods, like fast food,” said Caroline M. Apovian, MD, professor of medicine in the endocrinology department at Boston University School of Medicine. “More and more processed foods and the handling of food are causing ingestion of nonfood items, which may be harmful.”

Using data from the National Health and Nutrition Examination Survey from 2005 to 2014, the researchers studied everything eaten by the 10,253 participants in the previous 24 hours and looked at the levels of phthalate breakdown products in their urine samples.

Participants ranged from 6 to 85 years old. Researchers found phthalate levels were higher among adolescents.

Those teens — who had more of their meals at restaurants, fast-food places, and cafeterias — had 55 percent higher endocrine-disrupters compared with their peers who ate at home, said lead author Julia Varshavsky, PhD, postdoctoral scholar at the University of California at San Francisco Program on Reproductive Health and the Environment.

“All of the co-authors on this study have children, and they know that as kids get older, they tend to eat worse foods,” she said. “There’s something to be said about the change in children’s diets as they gain more independence and the potential to intervene to improve eating habits at an early age.”

What are phthalates?

Phthalates are a group of chemicals that are used to make plastics more flexible, but they’re also found in detergents, vinyl flooring, and multiple other products commonly used today.

The National Institute of Environmental Health Sciences classifies certain phthalates as “endocrine disruptors” that may “interfere with the body’s endocrine system and produce adverse developmental, reproductive, neurological, and immune effects in both humans and wildlife.”

The health effects from low-level exposure to phthalates is unknown in humans, and more research is needed, according to the Centers for Disease Control and Prevention (CDC). But the CDC notes phthalates have been found to affect the reproductive system in animals.

How fast food can affect phthalates exposure

In addition to finding a connection between increased phthalate levels and dining out, the study data also showed that consumption of cheeseburgers and sandwiches prepared outside the home was associated with 30 percent higher phthalate levels in participants of all ages.

The latest findings build on co-author Ami R. Zota’s previous study, which found that people who ate more fast food had higher levels of two particular types of phthalates than participants who reported eating no fast food in the last 24 hours.

“The reason we’re looking at dietary sources is because of the prior work that showed diet is a major source of exposure to phthalates,” said Varshavsky. “Phthalates are really relevant for children’s health and reproductive health.”

Studies have suggested that there may be associations between exposure to the endocrine-disrupting chemicals and lower IQ in children, higher risk of diabetes in women, increased likelihood of asthma, lower-quality sperm, and breast cancer.

“Endocrine-disrupting chemicals operate at the hormonal level, and since hormones operate at very low levels, so too can phthalates,” said Varshavsky.

How we’re exposed to phthalates through food

People are exposed to phthalates in hundreds of everyday products, including shower curtains, nail polish, detergents, and raincoats. But particular attention should be paid to dietary sources, since food also has nutritional effects on our health, said Varshavsky.

Phthalates aren’t intentionally added to foods. Rather, the research suggests that the chemicals might be leeching into foods that come into contact with plastic containers, tubing, and food-handling gloves and equipment.

“While our findings suggest that the source of your food matters, it doesn’t mean that what you’re putting into your body is no longer relevant,” she said. “Eating fresh foods prepared at home is better [for limiting phthalate exposure], and it’s the same advice given to people who want to reduce sodium, sugar, and fat in their diet, so it’s a win-win for health in that way.”

The Silent Spring Institute, a nonprofit organization that explores the connection between environmental chemicals and women’s health, offers several resources which may be useful for people looking to reduce their exposure to phthalates, said Varshavsky.

The organization’s tip sheet on phthalates and food recommends the following:

  • Eat meals prepared at home.
  • Choose fresh or frozen food over canned food.
  • Store leftovers in glass containers.
  • Use only heat-resistant glass or ceramic containers in the microwave.
  • Brew coffee in containers that don’t have plastic tubing.

While Varshavsky’s study indicates there’s a potential danger in dining out for many meals, she’s hopeful that the research will ultimately lead to a reduction in exposure to phthalates.

“This is a solvable problem. Phthalates have really short half-lives, and if we remove the source of contamination, we’ll see an immediate reduction in phthalate levels in people’s bodies,” she said.