Patulin

Every glass of apple juice carries a quiet question: did the fruit it came from carry mold? Patulin is one of the toxins that certain molds leave behind, and it turns up often enough in apple products that regulators cap how much is allowed in what you drink.

This test looks for patulin in your urine as a possible signal of recent exposure. It is an early-stage measurement, not a settled clinical tool, and the honest headline is that patulin is hard to catch in urine at all.

What Patulin Is

Patulin (sometimes shortened to PAT) is a mold toxin, meaning a poison made by fungi as they grow. It is produced mainly by mold species in the Penicillium and Aspergillus families, not by anything in your own body.

That is the key thing to understand: patulin is not something you make or need. It is a foreign substance you take in from food, so a result here reflects exposure, not a normal body process like kidney filtration or liver function.

Where Exposure Comes From

Apples and apple-based products are the main source of patulin for people. The mold that causes blue rot in apples is a heavy producer, and contamination of apple juice is described as a worldwide problem, which is why juice, cider, and concentrates are the usual suspects.

Exposure happens almost entirely through eating and drinking, not through the air or skin. Reported adult intake from food ranges from 0.63 to 21.2 nanograms per kilogram of body weight per day (a nanogram is a billionth of a gram), so typical daily amounts are very small.

For context, food safety limits are set on the food itself, not on your urine. In fruit juice for adults the cap is 50 micrograms per kilogram (millionths of a gram per kilogram), dropping to 10 micrograms per kilogram in products for infants and children, and the U.S. Food and Drug Administration sets 50 parts per billion in apple juice.

What Patulin Does in the Body

Most of what is known about patulin's harm comes from laboratory and animal research, so it should be read as biology to be aware of, not as proven effects in people at the exposures most of us encounter. In these studies, patulin reacts with sulfur-containing molecules inside cells, including glutathione (a molecule your cells use to neutralize damage), and this can trigger cell stress and cell death.

Animal and cell studies link high patulin doses to gastrointestinal, liver, kidney, immune, and nervous-system injury. Animal data also suggest that roughly a quarter to a third of an ingested dose is taken up from the stomach, then processed by the liver or kidneys and excreted in urine, which is the biological reason urine is even considered a possible testing matrix.

On cancer, the picture is unsettled and not alarming. The world's main cancer-classification body places patulin in Group 3, meaning there is not enough evidence to classify it as a cause of cancer in humans.

The Colorectal Cancer Question

The only human study to measure patulin in urine and blood side by side compared 50 people with colorectal cancer to 50 age- and sex-matched people without it. It found no meaningful difference in patulin levels between the two groups.

That null result does not prove patulin is harmless. It simply means this small study found no signal tying patulin exposure to that cancer, and it should temper any claim that a patulin reading reveals cancer risk.

Why Urine Is a Difficult Place to Measure This

Here is the most important caveat before you order this test. In that same human study, a validated specialized lab method (liquid chromatography paired with mass spectrometry) detected no patulin in any of the 100 urine samples, even though it found patulin in 25% of the paired blood samples, averaging 11.62 plus or minus 6.67 nanograms per milliliter among the positives.

Part of the reason is chemistry. Patulin is a very small, water-loving molecule, which makes it genuinely hard to capture and measure, and a 2019 review noted that there was no established information on patulin as a biomarker in biological samples at all.

It is also telling that a large 2025 study measuring 12 mycotoxins in the urine of Spanish adults did not even include patulin on its list of targets. So a non-detect on a urine test should be read cautiously: it may reflect low exposure, or it may reflect that urine is simply a poor window onto this particular toxin.

When a Single Reading Can Fool You

• Recent exposure only: because patulin clears the body quickly, a urine result reflects roughly the last day, not your long-term or cumulative intake. What you ate the day before the test matters more than your habits over months.
• Urine dilution: how much water you drank can concentrate or dilute the sample, which is why results are usually interpreted alongside urine creatinine (a marker used to correct for dilution).
• Spot versus timed collection: for fast-clearing substances, a single spot sample can miss an exposure that a full-day collection would catch, so one snapshot is easy to over-read.
• Detection limits: the toxin's small, polar structure means it can sit below what the assay can reliably see, so an undetectable result is not the same as zero exposure.

Reading a Result Over Time

For an exposure marker that clears quickly and is often undetectable, a single number tells you very little. The value, if any, comes from patterns: a baseline, a repeat after you change your diet, and occasional checks that let you see whether anything shows up repeatedly rather than once.

A sensible rhythm is a baseline reading, a follow-up in 3 to 6 months if you deliberately change how much apple juice or fruit product you consume, and periodic rechecks after that. Treat this as building your own exposure record over time, since there are no standardized clinical cutoffs to compare a lone reading against.

What an Unexpected Result Should Prompt

If patulin is detected, the first move is to confirm rather than react. Repeat the test with creatinine correction to account for dilution, and consider pairing it with a broader mycotoxin panel, since exposure to one mold toxin often travels with others and a wider view is more interpretable than a single marker.

From there, the practical steps are dietary and investigative: review your recent apple and juice intake, discard visibly moldy or spoiled fruit, and bring the pattern to a clinician or toxicology specialist who can judge whether an exposure-focused research assay is even relevant to your situation. A single detectable reading, on its own, is not a diagnosis and should not drive dramatic action.