Seven days without contact with plastic dramatically reduces phthalate and bisphenol levels in the body.

A paper entitled "Low-plastic diet and urinary levels of plastic-associated phthalates and bisphenols: the randomized controlled PERTH Trial" was published in Nature Medicine. The study focused not on microplastic particles, but on so-called plastic-associated chemicals—chemicals associated with plastic, primarily phthalates and bisphenols—which can enter the body through food, packaging, kitchenware, personal hygiene products, dust, and air.

The authors conducted their study in two parts. First, they conducted an observational cohort study of 211 healthy Australian adults to understand which daily habits were most strongly associated with urinary levels of these substances. Within this cohort, they then launched a seven-day pilot randomized trial in 60 participants, in which some participants were switched to the most "low-plastic" diet and lifestyle regimen.

The main question was very practical: is it possible to quickly reduce internal exposure to certain chemicals in plastic in real life by reducing the number of plastic "contact points" with food and personal care products? The researchers didn't ask people to fast or reduce their caloric intake, but rather tried to maintain their normal energy intake by simply replacing foods, packaging, some kitchenware, and some personal care products.

The study's main finding is this: over seven days, the low-plastic intervention did indeed reduce levels of some markers in urine, primarily mono-n-butyl phthalate, monobenzyl phthalate, and bisphenol A. However, the pattern wasn't universal: not all chemicals decreased equally, and for DEHP metabolites, the researchers actually observed an unexpected upward trend, making the paper's conclusion more complex and scientifically interesting than the simple slogan "less plastic, less of everything."

Key parameter	What the study showed
Magazine	Nature Medicine
Date of publication	April 21, 2026
DOI	10.1038/s41591-026-04324-7
Observation unit	211 healthy adults
Randomized part	60 participants
Duration of intervention	7 days
The Main Outcome	Changes in levels of plastic-related chemicals in urine
The most obvious decline	mono-n-butyl phthalate, monobenzyl phthalate and bisphenol A

Source for table: Nature Medicine article. [1]

How the PERTH Trial was organized

The cohort included 211 adults with an average age of 43.1 years, while the pilot randomized study included 60 individuals with an average age of 47.6 years. Participants were considered clinically healthy and were not pregnant or breastfeeding. Urine and nasal swab samples were collected repeatedly on different days to avoid relying on a single random measurement.

The randomized trial consisted of five groups of 12 participants. Group 1 received low-plastic food produced, processed, packaged, and delivered with minimal contact with plastic. Group 2 received the same food plus low-plastic kitchenware. Group 3 only changed personal hygiene products. Group 4 combined low-plastic food, kitchenware, and personal hygiene products. Group 5 received no intervention and served as a control.

The authors emphasize that the food intervention was unusually comprehensive: products were selected from over 100 producers, and the goal was to reduce plastic contact "from farm to plate." This meant not just transferring purchased food from plastic packaging to glass at home, but an attempt to reduce plastic at the production, processing, storage, transportation, and preparation stages.

The study was not a weight-loss program. Participants were asked to eat until satiation, consume only the food provided, and not to purchase additional food or deliberately alter their calorie intake. The authors report that the average daily energy intake was generally maintained across the food groups, and no safety concerns or adverse events were observed.

Group in RCT	What exactly was changed?
Group 1	Only low-plastic food
Group 2	Low-plastic food + kitchenware
Group 3	Only low-plastic personal hygiene products
Group 4	Food + kitchen utensils + personal hygiene products
Group 5	Without intervention

Source for table: PERTH RCT description. [2]

What the observation unit showed

The observational study provided important context for the intervention. The authors report that 100% of participants in the cohort excreted at least six plastic-related chemicals above the detection limit in their urine on any given day. This means that exposure to such substances for healthy adults was not a rare exception, but a nearly constant feature of everyday life.

When researchers tried to understand which habits were associated with higher levels of these substances, the most prominent factors emerged as highly processed foods, plastic-wrapped foods, and canned foods. In a cluster analysis, participants who were not enriched based on measured PAC tended to rarely eat fast food, highly processed foods, plastic-wrapped foods, and foods heated in plastic.

Non-food sources were also confirmed. The use of shampoo, makeup, and skin care products was positively associated with higher levels of certain low-molecular-weight phthalates in urine. This fits well with the long-discussed idea that plastic-associated chemicals enter the body not only through food but also through personal care products and cosmetics.

There were also more unexpected signals. For example, the authors observed a positive association between canned foods and beverages and bisphenol A, which seems expected, but also found a link between fruits and vegetables and bisphenol S, which they consider unusual and requires separate study. Furthermore, in this clinically healthy cohort, higher DEHP metabolites were unexpectedly associated with lower hsCRP and Lp(a) levels. The authors themselves explicitly state that this result requires verification in cohorts with cardiometabolic diseases and should not be interpreted as a proven "benefit" of DEHP.

What was associated with higher PAC levels?	What conclusion did the authors make?
Highly processed foods	One of the most prominent modifiable factors
Food in plastic packaging	Associated with higher levels of some metabolites
Canned food and drinks	Associated with higher bisphenol A
Shampoos, cosmetics, skin care products	Associated with low molecular weight phthalates
Reheating food in plastic containers and frequent consumption of fast food	Characteristic of clusters with higher exposure

Source for table: PERTH cohort observation unit. [3]

What the 7-day randomized intervention showed

The most striking result concerns comparisons with the control group. Group 2, where participants were given low-plastic food and kitchenware, showed a 37.5% reduction in mono-n-butyl phthalate, a 53.5% reduction in monobenzyl phthalate, and a 59.7% reduction in bisphenol A. These are precisely the figures cited in the abstract as the main finding of the randomized portion of the study.

But this group wasn't the only one that showed an effect. Group 1, which only changed food, showed a 31.5% reduction in mono-n-butyl phthalate, a 46.7% reduction in monobenzyl phthalate, and a 58.5% reduction in total bisphenols. Group 4, which changed food, kitchenware, and personal care products, showed the most significant reduction in mono-n-butyl phthalate—44.1%—and a 50.5% reduction in total bisphenols.

It's particularly important to note that replacing only personal hygiene products was significantly less effective. Group 3 reduced mono-n-butyl phthalate (MNP) by 35.3% compared to the control group, with no significant changes in bisphenol A. This supports the authors' idea that, in this study, plastic food contact surfaces were a more powerful and manageable source of exposure than personal hygiene products alone.

A crucial detail: the intervention reduced the Total Dietary Plastics Score across food groups, but did not lead to a universal decline in all metabolites. Conversely, the authors noted an unexpected increase in DEHP metabolites in the low-plastic food groups. They discuss several possible explanations: underreporting of DEHP content in food, additional non-food sources, and a possible slower "washout" profile for lipophilic compounds, especially if they interact with adipose tissue. This is one of the most insightful findings of the article: the problem of exposure to chemicals from plastics is not reducible to one simple pathway.

It's also important that the intervention didn't result in a significant deterioration in nutrition. Average caloric intake was maintained across the food groups, and body weight, body composition, and clinical biomarkers remained generally stable over such a short period. This suggests that the study demonstrates an acute effect on exposure to certain chemicals, rather than on clinical health outcomes.

Results compared to control	Change
Group 1: MnBP	-31.5%
Group 1: MBzP	-46.7%
Group 1: total bisphenols	-58.5%
Group 2: MnBP	-37.5%
Group 2: MBzP	-53.5%
Group 2: BPA	-59.7%
Group 3: MnBP	-35.3%
Group 4: MnBP	-44.1%
Group 4: total bisphenols	-50.5%

Source for table: main randomized part of the PERTH Trial. [4]

What does this mean and what the article does not yet prove?

The article's most powerful practical conclusion is that some everyday exposure to phthalates and bisphenols can indeed be reduced quite quickly by limiting highly processed foods, plastic packaging, and canned goods, and, where possible, reducing plastic contact with food throughout its preparation and storage. This doesn't seem like an abstract environmental recommendation: in a pilot RCT, markers were reduced in just seven days.

However, the article does not prove that such a week-long intervention improves health in a clinical sense. The changes in cardiovascular and inflammatory biomarkers in the RCT were descriptive and post hoc, and the study itself was primarily designed to measure changes in levels of plastic-related chemicals in urine. Therefore, it is impossible to draw conclusions like "a low-plastic diet treats metabolic disorders" from these data.

There are limitations, too. The authors were unable to directly test the levels of all these substances in the food already prepared at home by the participants, did not measure them in serum, adipose tissue, or feces, and used multiple spot samples pooled to estimate daily excretion rather than full 24-hour urine collections. Furthermore, the pilot RCT itself was relatively small and underpowered to reliably analyze differences by gender, body composition, and biomarkers.

Therefore, the correct conclusion is as follows: the PERTH Trial is a powerful and rare randomized human study for this topic, demonstrating that a low-plastic diet and lifestyle can significantly reduce some, but not all, markers of exposure to chemicals from plastic. For science, this is an important step from general concerns to testable interventions. For practice, it confirms that exposure sources are indeed modifiable, but the path from reducing urinary metabolites to proven clinical benefits is still to come.

How to correctly interpret the study	What does this mean in practice?
This is a pilot RCT plus cohort	The data is stronger than usual observation, but not yet conclusive.
Not all chemical markers decreased	The effect of the intervention is selective
The main outcome is urine levels, not disease.	Clinical benefit still needs to be proven
Food sources were found to be key	Packaging, canning and food processing matter
The DEHP result was unexpected	Longer and larger studies are needed

Source for table: discussion and limitations of the article. [5]

News source: Amelia J. Harray, Andrew D. Lucas, Susan E. Herrmann, et al. Low-plastic diet and urinary levels of plastic-associated phthalates and bisphenols: the randomized controlled PERTH Trial. Nature Medicine. Published April 21, 2026. DOI: 10.1038/s41591-026-04324-7.