Talk:Flavonoid

Outdated information in research and meteabolism

The research section is a bit outdated. The Linus Pauling Review has last been reviewed in 2016 and misses a number of reviews that have been published since, as well as e.g. new risk assessments for soy or tea catechins.

There are a lot of health claims for various flavonoids, so it might be useful to address them here and make it clear what the evidence says. The lack of essentiality does not say anything about health benefits - fibre is not essential yet has clear health benefits and a DRI/DRV - and the lack of DRV/DRI is also not evidence for a lack of health benefits, as the DRV/DRI process is mainly for essential nutrients and the introduction of other compounds is still under discussion.

The metabolism section could also be improved - there is a huge difference between different compounds, and an absorption of less than 5% is not correct (at least for some compounds, there is a considerably higher uptake). As bioavailability is interpreted slightly differently in nutrition research, it might be useful to be quite precise.

I'd be happy to draft something here if there is interest. Ggck2 (talk) 15:19, 27 August 2026 (UTC)

They have low oral bioavailability but the article does not mention technological approaches that have been used to enhance absorption. I have no idea how mainstream or widely used any of these improvement strategies are but this review covers the topic Carrot juice (talk) 20:00, 27 August 2026 (UTC)

There is an added problem that in nutrition, bioavailability is often used different than in pharmacology - so metabolites in various forms are included - so glucuronidation or sulphation does not affect bioavailability in that interpretation. It makes it somewhat confusing, but is nevertheless common practice. Ggck2 (talk) 21:27, 27 August 2026 (UTC)

The proposed draft on flavonoid metabolism seems beyond WP:NOTTEXTBOOK #6,7, and is WP:WFTWA. Zefr (talk) 22:01, 1 September 2026 (UTC)

Why would you say that updating information and making them accurate is WP:NOTTEXTBOOK? The metabolism section is simply outdated and wrong.

As per advice given, there is no need for a COI-template when discussing the article and not making edit requests. Ggck2 (talk) 05:49, 2 September 2026 (UTC)

On the subject of outdated things, I've restored the further reading section (but not any of the database removals). I don't think any of the books that were included in the section encroach on contentious medical things. I have no objection to removal of books that are not relevant, but I restored the section because Harborne's flavonoids is still one of the key all-time greats reviewing the diversity of flavonoids and their distribution across the plant kingdom. It's still factually relevant and it's probably the most widely-cited review of flavonoids ever. Elemimele (talk) 12:00, 14 September 2026 (UTC)

update?

I absolutely don't want to let this article get used to trumpet dubious health claims associated with flavonoids - nearly every paper that's ever been written seems to claim something extravagent - but the tone of the article does seem somewhat at odds with a few more up-to-date reviews such as these: . I am not expert at health matters so I'm just noting the references in case they're relevant to anyone else. My interest is only in flavonoid chemistry in plants... (hence my restoration of Harborne, above) Elemimele (talk) 12:05, 14 September 2026 (UTC)

Harborne is still one of the most relevant sources - and much written there doesn't change.

I wonder whether there is too much emphasis on health aspects and not enough on others. Flavonoids are such a diverse group of compounds that most health effects observed in epidemiological studies are most likely simply the result of a diet rich in fruits and vegetables; it's very different to separate the two. The fact that they are not recognised by any regulatory agency is therefore not really surprising.

What would be interesting would be to update data on ADME/PK. "Poorly absorbed" is not really correct, about 10% of catechins are absorbed, and nutritionists use a different definition of bioavailable (which is unfortunately often a bit confusing). "Rapid excretion" is therefore a bit too generic - some metabolites, especially from gut metabolism, can have half-lives of many hours. Considering the large number of flavonoids, there will be a huge amount of data which will probably be beyond the scope of this article - but it would be good to correct at least the statements that can't be generalised. Ggck2 (talk) 21:54, 14 September 2026 (UTC)

(I probably shouldn't really comment on Harborne, as he worked almost next door to our Department ...).

Ggck2 (talk) 08:10, 15 September 2026 (UTC)

Nutrient status and metabolism

Nutrients in human nutrition are generally considered to be compounds that are essential for live (dietary fibre is a bit of an exception as it is not essential) - not compounds that have an physiological effect (these are more commonly referred to as bioactive compound). The statement on nutrient status should therefore simply state:

1. Flavonoids are not considered as nutrients for humans as they are not essential for survival.

The data on metabolism is not correct - flavonoids are such a complex and diverse group of compounds that a single statement will never describe everything. In addition to this, flavonoid research often uses a slightly different definition of bioavailability, which includes metabolites and therefore can be confusing (e.g. depending on the interpretation, glycosides have a bioavailability of 0 as they are always deglycosylated - but some publications refer to the uptake of the aglycone). For example for the flavanol epicatechin, more than 80% of the compound are taken up by the human body in one form or another, and well over 10% are taken up as conjugated epicatechins (https://www.nature.com/articles/srep29034). Likewise, not all are rapidly excreted with plasma half-lives well above 6h for some compounds.

I think discussing this would go beyond the scope of this article, and suggest the following version revision:

1. The absorption and metabolism for flavonoids by the human body varies considerably between different compounds.[1][2][20][21][22] Flavonoids have negligible antioxidant activity in the body, and the increase in antioxidant capacity of blood seen after consumption of flavonoid-rich foods is not caused directly by flavonoids, but by production of uric acid resulting from flavonoid depolymerization and excretion.[1][2][3] Microbial metabolism is a major contributor to the overall metabolism of dietary flavonoids.[1][2][23]

Ggck2 (talk) 08:13, 20 September 2026 (UTC)

@Ggck2, you think the fact you research them gives you a conflict of interest? Valereee (talk) 15:42, 5 October 2026 (UTC)

@Valereee I have been told explicitly by @Zefr that I must not edit any page where I have a conflict of interest. In this instance, my conflict is based on the fact that I have received research funding from Mars to investigate the health effects of Flavanols. I don't want to fall foul of any rules - hence the edit request.

Ggck2 (talk) 17:27, 5 October 2026 (UTC)

Request declined as work-in-progress, unclear fates for metabolized flavonoids, and WP:UNDUE. Zefr (talk) 17:40, 5 October 2026 (UTC)

I'm sorry - the current statement is factually wrong:

Flavonoids are poorly absorbed in the human body (less than 5%)

Absorption varies significantly - and depending on definition, i.e. whether as intact molecule or metabolised. But [] shows about 40% of some flavanols are absorbed intact and then metabolised by the liver.

then are quickly metabolized into smaller fragments with unknown properties

Many flavonoids are not metabolised into smaller fragments - most are simply conjugated by the liver and then excreted (see e.g. []). This is the reason why flavonoid-metabolites in urine are used as markers of flavonoid intake (e.g. here [] or []. They are metabolised into smaller molecules by the gut microbiome which are then often taken up (there are quite a few studies - but [ probably provides most details. The pathways have been known for some times [] (apologies for citing work where I am a co-author - but this is one of the first studies explaining mechanisms).

and rapidly excreted.

Again - "rapidly" depends on the definition, but half lives of up to 28h [] are not really rapid.

This is the reason why I believe a simpler statement as the one suggested ("The absorption and metabolism for flavonoids by the human body varies considerably between different compounds.") describes the situation much better and takes the many differences into consideration.

Ggck2 (talk) 20:06, 5 October 2026 (UTC)

Outdated (2016) primary research on just 12 subjects, authored by Mars Inc. employees in support of the supplement, CocoaVia. Unambiguous COI source.

The comment "varies considerably between different compounds" doesn't help anyone understand the topic. Zefr (talk) 21:18, 5 October 2026 (UTC)

Please suggest how it could be revised. The current statement is however wrong - I have included more than a single source to support the statement. There is no secret about authorship and funding of the 14C study - but this doesn't change the outcomes and it provides a counter example to the statement in the article and there are not many 14C studies.

The 5% absorption rate is wrong - there is plenty of evidence (e.g. Crozier et al. - https://journals.sagepub.com/doi/full/10.1089/ars.2012.4581). Likewise, there is evidence to question the quick metabolism and rapid excretion.

Flavonoid metabolites are used as biomarkers of intake - that wouldn't be possible if this were true.

Ggck2 (talk) 07:34, 6 October 2026 (UTC)

Flavonoids as prescription drugs

The text

Due to the absence of proof for flavonoid health effects in clinical research, neither the United States FDA nor the European Food Safety Authority has approved any flavonoids as prescription drugs.[1][20][24][25]

is not entirely correct, as Catechin actually has been used as a drug more than 40 years ago (see Catechin#Adverse_events). It would also not be the European Food Safety Authority (EFSA) that approves drugs in Europe but the European Medicines Agency (EMA). I suggest the following change:

Flavonoid are currently not authorised as prescription drugs in Europe or the US.[1][20][24][25]

Ggck2 (talk) 08:29, 20 September 2026 (UTC)

Declined as trivial, outdated, and poorly sourced. Zefr (talk) 17:42, 5 October 2026 (UTC)

Flavonoid metabolism

There are factual errors in the article that should be addressed:

Flavonoids are poorly absorbed in the human body (less than 5%)

Absorption varies significantly - and depending on definition, i.e. whether as intact molecule or metabolised. But [] shows about 40% of some flavanols are absorbed intact and then metabolised by the liver.

then are quickly metabolized into smaller fragments with unknown properties

Many flavonoids are not metabolised into smaller fragments - most are simply conjugated by the liver and then excreted (see e.g. []). This is the reason why flavonoid-metabolites in urine are used as markers of flavonoid intake (e.g. here [] or []. They are metabolised into smaller molecules by the gut microbiome which are then often taken up (there are quite a few studies - but [ probably provides most details. The pathways have been known for some times [] (apologies for citing work where I am a co-author - but this is one of the first studies explaining mechanisms).

and rapidly excreted.

Again - "rapidly" depends on the definition, but half lives of up to 28h [] are not really rapid.

I therefore suggest the following change as it describes the current situation better:

The absorption and metabolism for flavonoids by the human body varies considerably between different compounds.

Ggck2 (talk) 20:12, 5 October 2026 (UTC)

@Zefr - you have declined the previous edit without any discussion. I believe my statement is correct and supported by facts - I do not suggest to cite any of the evidence I contributed here, but the evidence is sufficient to reject a claim of "poor absorption" and "rapid excretion". I would appreciate a discussion based on facts, not opinions. The current statement is factually wrong which is - I assume - worse than a statement that is difficult to understand. Ggck2 (talk) 21:39, 5 October 2026 (UTC)

• Declined: the information proposed for the article is trivial - WP:UNDUE, the compounds have no proven biological effects in amounts typically consumed, and the sources are either offtopic, self-cites by the COI editor, or 22+ years out of date. Zefr (talk) 19:22, 9 November 2026 (UTC)

  @Zefr - there is no claim about biological effects, but whether a compound has biological effects is not relevant for the definition of a nutrient (see e.g. the EFSA source). And there are no proposed citations, simply a correction of an oversimplification. Ggck2 (talk) 21:38, 9 November 2026 (UTC)