The metabolism of many #polyphenols is superbly described by @phisquarelab @anarmateos @Prof_JPESpencer in their outstanding review (https://www.ncbi.nlm.nih.gov/pubmed/22794138 ) - showing that what could act as antioxidant quickly disappears, courtesy of metabolising enzymes.pic.twitter.com/iOaEbH4h6Z
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A detailed study of one particular
#polyphenol, the#flavanol#epicatechin showed that there is virtually no pure compound in circulation - only metabolites. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4929566/ …pic.twitter.com/QO7udXUzUE
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So they are not
#antioxidants in vivo - and there are huge differences in metabolism between humans and animals, making data from animal studies rather unreliable. Even cell-culture studies are difficult to conduct as for most compounds, metabolites are not easily available.pic.twitter.com/EbpJP3POFm1 reply 0 retweets 4 likesShow this thread -
What about human studies? There are many intervention studies that report a beneficial effect of
#polyphenols - but it is important to distinguish between food and compound. An apple is primarily an apple - not just plain packaging for#flavanols.pic.twitter.com/cwNZmqx5jt1 reply 1 retweet 8 likesShow this thread -
The same applies to tea, berries or chocolate - they are primarily foods. It is difficult to obtain pure compounds, so foods are often used as alternative - but one has to be careful to extrapolate the effect of pure compounds.
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The same problem applies to population studies - they usually have to rely on dietary data to estimate intake of compounds, and there is again a difference between a glass of Argentinian Malbec and pure resveratrol, or an Apple and pure epicatechin.pic.twitter.com/PBVrOOdp6P
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Results from observational studies are actually quite weak - for example for flavanol, they do not show an overall clinically significant effect in either direction.pic.twitter.com/PRU653bqRZ
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Thus it is very difficult to differentiate between the effect of
#polyphenols in the diet - and the dietary pattern that provides polyphenols. The latter is undoubtedly healthy, as it includes a large variety of fruits and vegetables.pic.twitter.com/2dv31aDnz11 reply 0 retweets 9 likesShow this thread -
But there are two more points: Firstly,
#polyphenols is a class of compounds with a huge number of members (https://www.springer.com/gp/book/9780412224805 …) - it is unlikely that they all have the same effect on health. Secondly: if they have an effect on health - why should it be only beneficial?1 reply 1 retweet 5 likesShow this thread -
The adverse effects of green tea extract (liver damage) is well known, as are the dangers of
#curcumin. But there are#polyphenols where habitual intake is cause for concern.2 replies 0 retweets 6 likesShow this thread
I haven't read much on the dangers of curcumin. Any good links?
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Replying to @GidMK
There are a few case reports - e.g. here:https://www.hindawi.com/journals/crihep/2019/6741213/ …
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