Flavanols
Flavanols, also called flavan-3-ols or catechins, are a subclass of flavonoids. Cocoa is rich in them, and studies have measured them after people ate tea, cocoa, apples, grapes and nuts.
What it means in practice
Flavanols come as single units (monomers) and as linked chains called proanthocyanidins [4]. A 2008 review describes flavan-3-ols and proanthocyanidins as the most common flavonoid in the American diet [4]. Foods differ in which forms they carry: some contain only monomers, in which (-)-epicatechin predominates, plus two-unit chains, while most foods contain chains with a degree of polymerization of 1-10 or greater than 10 [4]. Degree of polymerization is simply the number of units joined together.
Flavanols are heavily modified in the body. A systematic review of 49 human intervention studies counted up to 180 metabolites in blood and urine after flavan-3-ol intake, mostly gut-microbe breakdown products that the body had further modified [3]. Mean bioavailability, the share that reaches the circulation, was 31 ± 23% [3].
Why it matters when reading nootropics research
Flavanol amounts in studies vary widely. Trials in a Cochrane review of cocoa products provided 30 to 1218 mg of flavanols a day, in 1.4 to 105 grams of cocoa product [5]. A paper may report total flavanols, a single compound such as (-)-epicatechin, or only the weight of chocolate or cocoa, so it helps to check which one before comparing two studies.
The source food also matters. In the 49-study systematic review, mean bioavailability was 82% after (-)-epicatechin taken on its own, a figure from a single study, but 25% after tea, cocoa, apples and grape [3]. Regulators specify the form too: in the Great Britain nutrition and health claims register, the cocoa flavanol claim can be used only for cocoa extract capsules or tablets, cocoa beverages or dark chocolate providing at least 200 mg of cocoa flavanols a day with a degree of polymerization of 1-10 [6].
For the graded evidence on cocoa flavanols, see Cocoa flavanols.
References
- Panche AN, Diwan AD, Chandra SR. Flavonoids: an overview. J Nutr Sci. 2016.
- Cifuentes-Gomez T, Rodriguez-Mateos A, Gonzalez-Salvador I, et al. Factors Affecting the Absorption, Metabolism, and Excretion of Cocoa Flavanols in Humans. J Agric Food Chem. 2015.
- Di Pede G, Mena P, Bresciani L, et al. Revisiting the bioavailability of flavan-3-ols in humans: A systematic review and comprehensive data analysis. Mol Aspects Med. 2023.
- Aron PM, Kennedy JA. Flavan-3-ols: nature, occurrence and biological activity. Mol Nutr Food Res. 2008.
- Ried K, Fakler P, Stocks NP. Effect of cocoa on blood pressure. Cochrane Database Syst Rev. 2017.
- Department of Health and Social Care (GOV.UK). Great Britain nutrition and health claims (NHC) register (spreadsheet, 19 May 2026; cocoa rows). Updated May 19, 2026.