Apple intake tracked through urine biomarkers
What it found
In 30 healthy people, levels of three compounds in urine rose after eating apples and could tell apart a large apple portion from a small or medium one.
The compounds were mostly gone from urine by the next morning.
What they found
Studies in people
Phloretin rises quickly
Phloretin in urine rose right after the apples were eaten and peaked about 3 hours later in every group. Levels stayed higher than the before-apple sample for the rest of the day.
Telling portions apart
Summed phloretin over the consumption day clearly separated the four-apple group from the one-apple and two-apple groups. The difference between one and two apples was less clear.
Epicatechin and procyanidin B2
Epicatechin and procyanidin B2 also rose after apples and peaked within a few hours. Both could separate a large portion from a small or medium one, but not a small portion from a medium one.
Gone by next morning
By the morning after the apple day, the researchers could no longer tell those samples apart from the samples taken before any apples were eaten. The authors call these short-term markers only.
Quercetin not useful
Quercetin was mostly found at levels too low to measure, so no statistics were done on it. The authors question whether it works as an apple marker because onions are a bigger source.
Wide person-to-person spread
The amounts excreted varied a lot between individuals, even within the same apple portion group. Some people in the two-apple group excreted more than some in the four-apple group.
What the authors conclude
- They conclude that phloretin, epicatechin and procyanidin B2 can be used as short-term biomarkers for apple consumption.
- They say these markers can distinguish between low and high apple consumption and are not influenced by a varied daily diet.
- They recommend collecting spot urine samples over 1 to 3 months to assess a person's usual apple intake, since the markers are mostly gone 24 hours after eating apples.
How it was done
The authors wanted an objective way to check how much apple people eat, because food questionnaires and diaries are subjective and prone to error. Apples were chosen because they are the most consumed fruit in Germany.
Thirty healthy adults, 14 women and 16 men with a mean age of 26.7 years, avoided all apples and apple products for seven days except for one weighed portion on day 3. They were split into three groups of ten and given 200 g, 400 g or 790 g of Boskoop apple pieces, matching one, two or four apples, then collected spot urine samples over the following days.
What it can’t tell you
- This was a short study of 30 people, so it cannot show what happens with long-term apple eating.
- The markers are not specific to apples, so the study cannot prove that all the measured compounds came only from the apples eaten.
- The study did not test whether these markers link to any health outcome.
Who paid
- Authors work at
- Westfälische Wilhelms-Universität Münster, Germany
The paper
- Title
- Short-term biomarkers of apple consumption
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Saenger T, Hübner F, Humpf HU (2017). Short-term biomarkers of apple consumption. Molecular nutrition & food research. doi:10.1002/mnfr.201600629Free full textPubMed 27794196DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error