A trial in Perth, Australia, found lower levels of some plastic-associated chemicals in the urine of people supplied with food specially sourced to minimise plastic contact. Researchers worked with more than 100 farmers and producers to reduce that contact during production, processing, packaging and supply. The intervention went well beyond transferring supermarket food into different containers at home. Nature Medicine / PubMed Central (source, opens in new tab)
Nature Medicine / PubMed CentralLow-plastic diet and urinary levels of plastic-associated phthalates and bisphenols: the randomized controlled PERTH TrialOpen source (opens in new tab)
Researchers measured bisphenols and phthalate breakdown products in participants’ urine. Bisphenols and phthalates are two groups of chemicals associated with plastics and other consumer products. These urine measurements indicate exposure to selected chemicals; they do not measure the total amount of plastic-related chemicals in the body.
The PERTH pilot trial randomly assigned 60 adults to five groups of 12. For seven days, they received the specially sourced food alone; food plus replacement kitchenware; replacement personal-care products alone; all three measures; or no intervention. The personal-care products included shampoo, moisturiser and deodorant screened by the researchers to minimise exposure to plastic-associated chemicals. The control group continued its usual diet and lifestyle.
At the end of the week, urinary total bisphenols were estimated to be 50.5% lower in the group receiving all three measures than in the control group. The food-only group had 58.5% lower total bisphenols than the control group. The larger percentage for food alone does not establish that it worked better than the combined intervention; the trial was small, and the reported estimates compare each group with the control rather than directly with each other. These percentages describe differences between groups at the end of the trial—not how far participants’ levels fell from their own measurements before it began.
The findings do not establish that participants became healthier or that the differences would persist beyond the seven-day intervention.
The kitchenware comparison needs particular care. Participants receiving food alone continued using their own cookware and utensils. Those receiving food plus kitchenware were supplied with alternatives made from metal, glass or uncoated wood. There was no kitchenware-only group, so the study did not test replacing kitchenware while leaving the food supply unchanged.
The results varied by chemical and by intervention. The personal-care-products-only group had lower levels of a phthalate breakdown product called MnBP than the control group, but no statistically significant difference in urinary bisphenols. Meanwhile, urinary breakdown products of another phthalate, DEHP, increased within some intervention groups. That increase remains unexplained. The findings therefore do not support a blanket reduction across plastic-related chemicals.
Changes in the control group also affected the comparisons. Across the three groups receiving the specially sourced food, levels of two phthalate breakdown products, MBzP and MnBP, were estimated to be 44.5% and 37.9% lower than in the control group. Yet the control group’s levels rose by 54.5% and 40.2%, respectively, during the week. Those increases contributed to the gap between the groups. The reported differences therefore cannot be read as equivalent falls within the food groups.
This was a small, exploratory trial. Researchers chose the sample size on practical grounds, without formally calculating how many participants would be needed to detect an effect. Larger, longer studies would be needed to establish whether the changes persist and whether reducing these exposures benefits health. The study was funded by the Minderoo Foundation.
- Nature Medicine / PubMed Central · Peer-reviewed studyLow-plastic diet and urinary levels of plastic-associated phthalates and bisphenols: the randomized controlled PERTH Trialpmc.ncbi.nlm.nih.gov · opens in new tab
