According to the study, dining out more at restaurants, cafeterias, and fast-food outlets may increase total levels of potentially health-harming chemicals called pthalates in the body

Pthalates, a group of chemicals used in food packaging and processing materials, are known to disrupt hormones in humans and are linked to a long list of health problems.

The present study is the first to compare phthalate exposures in people who reported dining out to those more likely to enjoy home-cooked meals. People who reported consuming more restaurant, fast food, and cafeteria meals had phthalate levels that were nearly 35% higher than people who reported eating food purchased mostly at the grocery store.

Lead author Julia Varshavsky, Ph.D., MPH, and their colleagues used data from the National Health and Nutrition Examination Survey (NHANES) collected between 2005 and 2014.

The 10,253 participants in the study were asked to recall what they ate and where their food came from in the previous 24 hours. The researchers then analyzed the links between what people ate and the levels of phthalate break-down products found in each participant's urine sample.

The team found that 61% of the participants reported dining out the previous day. A previous study by Zota and colleagues suggested that fast food may expose consumers to higher levels of phthalates. That study found that people who ate the most fast food, burgers, fries and other foods, had phthalate levels that were as much as 40% higher than people who rarely ate such foods.

The new study looked more broadly at dining out—not just at fast-food outlets—and found that it was significantly associated with increased exposure to phthalates. The authors say the findings are worrisome because two-thirds of the U.S. population eats at least some food outside the home daily.

The team used an innovative method of assessing real-world exposures to multiple phthalates, called cumulative phthalate exposure, which takes into account evidence that some phthalates are more toxic than others. 

The National Academies of Sciences has weighed in twice on phthalates—first, in a 2008 report, they recommended using cumulative risk assessments to estimate the human health risk posed by this class of chemicals; and then in 2017 with a report finding that certain phthalates are presumed to be reproductive hazards to humans.

Many products contain phthalates, including take-home boxes, gloves used in handling food, food processing equipment, and other items used in the production of restaurant, cafeteria and fast food meals.

Previous research suggests these chemicals can leach from plastic containers or wrapping into food. If verified by additional research, the findings from this study suggest that people who love dining out are getting a side of phthalates with their entrée.

At the same time, phthalate contamination of the food supply also represents a larger public health problem, one that must be addressed by policymakers. Zota and Woodruff's previous research shows that policy actions, such as bans, can help reduce human exposure to harmful phthalates.