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Story checked

Polyphenol Oxidase in Fruit: What the Smoothie Claims Get Wrong (opens in a new tab)

menshealth.com · 2026-09-23

Short answerEvidenceSource

Short answer

Mixed

Mixed.

One key claim is not backed by the study. One other point was not covered by the paper.

  • 2 supported
  • 2 overstated
  • 1 not supported
  • 1 not covered

Checked against the study summary. The full text wasn't available, so some details couldn't be settled either way.

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Follow the evidence trail
1
2

NewsLink checks it

Mixed

Three claims go beyond the study. Two overstate it and one isn't supported at all. One claim the study doesn't address.

  • 2 supported
  • 2 overstated
  • 1 not supported
  • 1 not covered
Open claim evidence
3
Then inspect each claim

Evidence layer

Claim by claim

Each claim gets a verdict. Expand it to see the evidence directly below.

6 claims in this story

Showing all 6 claimsChoose a verdict to focus the list.

Claim 1 of 6Not supportedSocial media claims said bananas can destroy 84 percent of the antioxidants found in food and supplements, fueling fear about adding bananas to smoothies.View evidenceHide evidence

As stated84 percent of the antioxidants

Why this verdict

The paper profile does not support the quoted viral claim that bananas 'destroy 84 percent of the antioxidants' in food or supplements. The abstract-level evidence reports an 84% lower peak plasma concentration of flavan-3-ol metabolites after a high-PPO banana-based drink compared with capsule intake, not destruction of antioxidants generally. The existence and wording of social media claims is also outside the paper evidence.

1

Study evidence

Peak plasma concentration (Cmax) of flavan-3-ol metabolites after capsule intake was 680 ± 78 nmol L-1; levels after the low-PPO mixed berry drink were reported as similar to the capsule.680 ± 78 nmol L-1 (capsule); low-PPO drink similar

“a controlled, single blinded and cross-over study was conducted in healthy men (n = 8) who consumed a flavan-3-ol-containing banana-based smoothie (high-PPO drink), a flavan-3-ol-containing mixed berry smoothie (low-PPO drink) and flavan-3-ols in a capsule format (control).”
Claim 2 of 6OverstatedThe story says a 2023 controlled, single-blinded, cross-over study in 19 men found banana-containing smoothies delivered fewer amounts of one specific subset of polyphenols, flavan-3-ols, compared with fruit smoothies without bananas.View evidenceHide evidence

Why this verdict

The core finding is supported: a high-PPO banana-based smoothie was associated with much lower plasma flavan-3-ol metabolite Cmax than low-PPO mixed berry smoothie/capsule conditions. But the story states this as a single controlled, single-blinded cross-over study in 19 men; the profile describes a primary cross-over study in healthy men with n=8 plus a separate follow-up study with n=11. The wording 'delivered fewer amounts' is also less precise than the paper's bioavailability endpoint.

1

Study evidence

Peak plasma concentration (Cmax) of flavan-3-ol metabolites after capsule intake was 680 ± 78 nmol L-1; levels after the low-PPO mixed berry drink were reported as similar to the capsule.680 ± 78 nmol L-1 (capsule); low-PPO drink similar

“a controlled, single blinded and cross-over study was conducted in healthy men (n = 8) who consumed a flavan-3-ol-containing banana-based smoothie (high-PPO drink), a flavan-3-ol-containing mixed berry smoothie (low-PPO drink) and flavan-3-ols in a capsule format (control).”
2

Study evidence

Prevention of pre-ingestion contact between flavan-3-ols and a high-PPO banana drink did not prevent reduced plasma flavan-3-ol levels; levels remained lower than control, suggesting post-ingestion PPO-related degradation.

“In a subsequent study (n = 11), flavan-3-ols were co-ingested with a high-PPO banana drink but contact prior to intake was prevented.”
Claim 3 of 6OverstatedThe article concludes people should not worry about polyphenol oxidase and should keep eating and drinking bananas and focus on getting enough fruits and vegetables instead.View evidenceHide evidence

Why this verdict

The paper does not provide dietary guidance that people need not worry about PPO or should simply keep eating/drinking bananas. It reports a substantial reduction in flavan-3-ol metabolite bioavailability with a high-PPO banana drink under study conditions. General advice about banana consumption and fruit/vegetable intake may be reasonable public-health messaging, but it is broader than what this abstract-level paper directly tests.

1

Study evidence

Peak plasma concentration (Cmax) of flavan-3-ol metabolites after capsule intake was 680 ± 78 nmol L-1; levels after the low-PPO mixed berry drink were reported as similar to the capsule.680 ± 78 nmol L-1 (capsule); low-PPO drink similar

“a controlled, single blinded and cross-over study was conducted in healthy men (n = 8) who consumed a flavan-3-ol-containing banana-based smoothie (high-PPO drink), a flavan-3-ol-containing mixed berry smoothie (low-PPO drink) and flavan-3-ols in a capsule format (control).”
2

Study evidence

Prevention of pre-ingestion contact between flavan-3-ols and a high-PPO banana drink did not prevent reduced plasma flavan-3-ol levels; levels remained lower than control, suggesting post-ingestion PPO-related degradation.

“In a subsequent study (n = 11), flavan-3-ols were co-ingested with a high-PPO banana drink but contact prior to intake was prevented.”
Claim 4 of 6Not coveredPolyphenol oxidase is a naturally occurring enzyme that causes plants to degrade and is what causes fruits and vegetables to brown.View evidenceHide evidence

Why this verdict

The paper abstract/profile supports that PPO activity was measured across fruits, vegetables, and plant-derived products, but it does not state at this depth that PPO is the enzyme responsible for fruit and vegetable browning or plant degradation. That may be generally true background, but it is not verifiable from the supplied abstract-level profile.

1

Study evidence

A substantial range in polyphenol oxidase (PPO) activity was detected among 18 fruits, vegetables, and plant-derived dietary products.

“There was a substantial range in the PPO activity detected in 18 different fruits, vegetables and plant-derived dietary products.”
Claim 5 of 6SupportedThe article says influencers have claimed that adding bananas to blueberries or smoothies significantly reduces polyphenols, but that the cited study found something less dramatic.View evidenceHide evidence

As statedquite a bit lower

Why this verdict

The paper supports the article's corrective point that the cited study was narrower than broad claims about bananas reducing all polyphenols: it measured plasma bioavailability of flavan-3-ol metabolites and found lower Cmax after a high-PPO banana drink. The profile does not verify what influencers said, but the story's framing that the study found a less sweeping result is consistent with the paper.

1

Study evidence

Peak plasma concentration (Cmax) of flavan-3-ol metabolites after capsule intake was 680 ± 78 nmol L-1; levels after the low-PPO mixed berry drink were reported as similar to the capsule.680 ± 78 nmol L-1 (capsule); low-PPO drink similar

“a controlled, single blinded and cross-over study was conducted in healthy men (n = 8) who consumed a flavan-3-ol-containing banana-based smoothie (high-PPO drink), a flavan-3-ol-containing mixed berry smoothie (low-PPO drink) and flavan-3-ols in a capsule format (control).”
Claim 6 of 6SupportedThe article says the study was used to create fear about bananas in smoothies, but it only reduced one polyphenol group and should not be taken to mean a varied diet or a smoothie’s overall healthfulness is harmed.View evidenceHide evidence

Why this verdict

The paper evidence is limited to flavan-3-ol metabolite bioavailability, with no assessment of total antioxidants, all polyphenols, overall smoothie healthfulness, or varied-diet health outcomes. Therefore the article's caution that the study should not be generalized into broad fear about bananas or smoothie healthfulness is supported by the narrow scope of the findings.

1

Study evidence

Peak plasma concentration (Cmax) of flavan-3-ol metabolites after capsule intake was 680 ± 78 nmol L-1; levels after the low-PPO mixed berry drink were reported as similar to the capsule.680 ± 78 nmol L-1 (capsule); low-PPO drink similar

“a controlled, single blinded and cross-over study was conducted in healthy men (n = 8) who consumed a flavan-3-ol-containing banana-based smoothie (high-PPO drink), a flavan-3-ol-containing mixed berry smoothie (low-PPO drink) and flavan-3-ols in a capsule format (control).”
2

Study evidence

Prevention of pre-ingestion contact between flavan-3-ols and a high-PPO banana drink did not prevent reduced plasma flavan-3-ol levels; levels remained lower than control, suggesting post-ingestion PPO-related degradation.

“In a subsequent study (n = 11), flavan-3-ols were co-ingested with a high-PPO banana drink but contact prior to intake was prevented.”
Then look for missing context

Context layer

What the story left out

Important study details the story did not include.

  • Follow-up human study: in a separate n=11 study, reduced plasma flavan-3-ol levels persisted when pre-ingestion contact between flavan-3-ols and the high-PPO banana drink was prevented, suggesting a possible post-ingestion PPO-related mechanism.

    The story does not mention the separate follow-up experiment or the mechanistic inference about possible post-ingestion/stomach effects.

    From Human co-ingestion intervention with contact-prevention (n = 11)

  • Food-chemistry element: PPO activity varied substantially across 18 fruits, vegetables, and plant-derived dietary products measured in vitro.

    The story discusses PPO generally as a browning enzyme, but it does not reflect the paper's product-level PPO activity survey or its abstract-level limitations.

    From in vitro enzymatic activity survey

  • Important limitation: the human studies were small and demographically limited at abstract depth, with n=8 in the primary cross-over study and n=11 in the follow-up; the abstract lacks details on randomization, washout, full pharmacokinetics, statistical testing, and analytic methods.

    The story mentions '19 men,' but this merges two separate studies and does not reflect the primary study's very small n=8, the separate n=11 follow-up, or the missing methodological/statistical details available only beyond the abstract.

    From Controlled, single-blinded, cross-over human dietary intervention; Human co-ingestion intervention with contact-preventi

3 things the story did carry across
  • Primary human intervention: a controlled, single-blinded cross-over study in healthy men compared a high-PPO banana-based smoothie, a low-PPO mixed berry smoothie, and a flavan-3-ol capsule control, measuring plasma flavan-3-ol metabolite Cmax.
  • Main quantitative result: the high-PPO banana drink produced a Cmax of 96 ± 47 nmol L-1, reported as 84% lower than capsule intake; the low-PPO drink was similar to capsule.
  • Scope limitation: the paper assessed flavan-3-ol metabolite bioavailability, not total antioxidant content, all polyphenols, long-term health outcomes, smoothie healthfulness, or effects of a varied diet.
Then read the study layer

Study layer

Study at a glance

Scan the study first. Expand only the parts you want to inspect.

Pieces of work

3

Evidence read

study summary

Lead result

human in vivo

1Lead resulthuman in vivoDetermine whether consuming flavan-3-ols in freshly prepared smoothies made with high vs low polyphenol oxidase (PPO) fruit alters plasma bioavailability of flavan-3-ol metabolites compared with a capsule control in healthy men.Controlled, single-blinded, cross-over human dietary interventionExpand

In plain English

A controlled, single-blinded, cross-over dietary intervention in healthy men (n = 8) compared plasma peak concentrations (Cmax) of flavan-3-ol metabolites after intake of a high-PPO banana-based smoothie, a low-PPO mixed-berry smoothie, and a flavan-3-ol capsule control. The capsule and low-PPO drink produced similar Cmax values, whereas the high-PPO drink produced a markedly lower Cmax. A separate follow-up study (n = 11) in which contact prior to intake was prevented still showed reduced plasma levels with the high-PPO banana drink, suggesting a possible post-ingestion PPO-related effect.

Key findings

  • Peak plasma concentration (Cmax) of flavan-3-ol metabolites after capsule intake was 680 ± 78 nmol L-1; levels after the low-PPO mixed berry drink were reported as similar to the capsule.680 ± 78 nmol L-1 (capsule); low-PPO drink similar
  • Intake of the high-PPO banana-based drink resulted in a Cmax of 96 ± 47 nmol L-1, reported as 84% lower than the capsule Cmax.96 ± 47 nmol L-1 (Cmax); 84% lower vs capsule
“a controlled, single blinded and cross-over study was conducted in healthy men (n = 8) who consumed a flavan-3-ol-containing banana-based smoothie (high-PPO drink), a flavan-3-ol-containing mixed berry smoothie (low-PPO drink) and flavan-3-ols in a capsule format (control).”
What this piece can’t prove
  • Abstract does not report full pharmacokinetic parameters beyond Cmax, nor does it report statistical significance testing or detailed analytical methodology.

3 further details could not be confirmed from the summary.

2human in vivoTest whether reduced flavan-3-ol bioavailability with a high-PPO banana drink persists when pre-ingestion contact between flavan-3-ols and the high-PPO matrix is prevented (mechanistic probe consistent with post-ingestion/stomach effects).Human co-ingestion intervention with contact-prevention (n = 11)Expand

In plain English

Follow-up human intervention (n = 11) in which flavan-3-ols were co-ingested with a high-PPO banana drink but contact prior to intake was prevented; plasma flavan-3-ol levels remained reduced, leading the authors to suggest post-ingestion (stomach) PPO activity as a possible mechanism.

Key findings

  • Prevention of pre-ingestion contact between flavan-3-ols and a high-PPO banana drink did not prevent reduced plasma flavan-3-ol levels; levels remained lower than control, suggesting post-ingestion PPO-related degradation.
“In a subsequent study (n = 11), flavan-3-ols were co-ingested with a high-PPO banana drink but contact prior to intake was prevented.”
What this piece can’t prove
  • Mechanistic claim (post-ingestion PPO activity) is inferential from the persistence of reduced plasma levels and is not directly tested or measured in this reported experiment.

2 further details could not be confirmed from the summary.

3in vitroCharacterize the range of PPO activity across a set of fruits, vegetables, and plant-derived dietary products relevant to food preparation.in vitro enzymatic activity surveyExpand

In plain English

An in vitro survey measured polyphenol oxidase (PPO) enzymatic activity across 18 fruits, vegetables, and plant-derived dietary products and found substantial variation in activity among the products.

Key findings

  • A substantial range in polyphenol oxidase (PPO) activity was detected among 18 fruits, vegetables, and plant-derived dietary products.
“There was a substantial range in the PPO activity detected in 18 different fruits, vegetables and plant-derived dietary products.”
What this piece can’t prove
  • Representativeness of the 18 sampled products for broader food categories is not specified.

2 further details could not be confirmed from the summary.

Finally, the search trail

Method layer

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Papers considered

The selected paper, plus nearby candidates.

PubMed, Europe PMC, Crossref · 15 candidate papers

Candidate

Bioavailability of Dietary Monomeric and Polymeric Flavan-3-ols

Flavonoids and Related Compounds · 2012 · Crossref

Source (opens in a new tab)

And 9 more candidates considered.