Catechins

1. What This Class of Substances Is

Catechins are a subgroup of flavonoids, secondary plant compounds with antioxidant properties. They are found primarily in green tea (epigallocatechin gallate, EGCG) and cocoa (epicatechin, catechin). Chemically, they are polyphenols with multiple hydroxyl groups that can neutralise free radicals and modulate enzyme activities. Green tea contains up to 30% catechins by dry weight, while cocoa contains up to 10%. Bioavailability varies widely: whereas EGCG from green tea is poorly absorbed, cocoa flavanols show better uptake, particularly in glucuronidated or sulphated forms.

The effects of catechins are difficult to measure directly in humans, as they are rapidly metabolised in the body and excreted via the kidneys. Blood levels of EGCG reach only low concentrations after oral intake, whereas cocoa flavanols are detectable in higher amounts. Additionally, catechins interact with other dietary components (e.g., milk proteins), which affects their absorption. Controlled studies therefore often use biomarkers such as endothelial function, inflammatory parameters, or lipid profiles to capture indirect effects.

2. Which Materials Are Included

All substances in the database for which this mechanism of action is described—ordered by the extent of human testing. The numbers represent studies per type of investigation.

3. How Robust the Evidence Is

Green tea (EGCG) and cocoa flavanols are the most extensively studied catechin sources, with over 70 controlled human trials each. Both show consistent evidence of cardiovascular effects, such as improved vascular function or reduced LDL cholesterol. Other catechin sources, such as grape seed extract (OPC) or pine bark extract, are significantly less researched, although laboratory and animal studies suggest similar mechanisms. Humic acid complexes, resveratrol, or quercetin have scarcely any clinical data and are primarily based on cell or animal models.

Catechins from different sources share similar antioxidant and anti-inflammatory mechanisms, such as the inhibition of NF-κB or the activation of Nrf2. While extrapolating findings from green tea or cocoa to other catechin sources is plausible, it is not substantiated. For example, controlled studies on the synergistic effects of catechins with other polyphenols (e.g., in berries) or on long-term effects in chronic diseases are lacking. The role of the gut microbiome in catechin metabolism is also only preliminarily investigated.

4. Key Human Studies

• 1 Antiobesity effects of green tea catechins: a mechanistic review (2011) — Green tea and EGCG
• 2 Potential role of green tea catechins in various disease therapies: progress and promise (2012) — Green tea and EGCG
• 3 Randomized, Placebo-Controlled Trial of Green Tea Catechins for Prostate Cancer Prevention (2015) — Green tea and EGCG
• 4 Flavonoid-rich dark chocolate improves endothelial function and increases plasma epicatechin concentrations in healthy adults (2004) — Cocoa flavanols
• 5 Chronic ingestion of flavan-3-ols and isoflavones improves insulin sensitivity and lipoprotein status and attenuates estimated 10-year CVD risk in med (2012) — Cocoa flavanols
• 6 Effect of cocoa flavanol supplementation for the prevention of cardiovascular disease events: the COcoa Supplement and Multivitamin Outcomes Study (COSMOS) (2022) — Cocoa flavanols
• 7 Polyphenol Intervention Ameliorates Non-Alcoholic Fatty Liver Disease: An Updated Comprehensive Systematic Review (2024) — Turmeric and curcumin
• 8 Effects of Dietary Components on Mast Cells: Possible Use as Nutraceuticals for Allergies? (2023) — Turmeric and curcumin
• 9 Potential Effects of Bioactive Compounds of Plant-Based Foods and Medicinal Plants in Chronic Kidney Disease and Dialysis: A Systematic Review (2024) — Turmeric and curcumin
• 10 Treatment of ADHD with French maritime pine bark extract, Pycnogenol (2006) — Pine bark extract
• 11 Pycnogenol, French maritime pine bark extract, augments endothelium-dependent vasodilation in humans (2007) — Pine bark extract
• 12 Distribution of Constituents and Metabolites of Maritime Pine Bark Extract (Pycnogenol^®) into Serum, Blood Cells, and Synovial Fluid of Patients (2017) — Pine bark extract
• 13 Effects of 2-year cocoa extract supplementation on inflammaging biomarkers in older US adults: findings from the COcoa Supplement and Multivitamin Outcomes Study (COSMOS) (2025) — Chronic inflammation
• 14 Nutraceutical enhancement of paraoxonase 1 activity in chronic inflammation: A systematic review of animal-based and plant-based nutraceuticals (2026) — Chronic inflammation
• 15 Effect of Epigallocatechin Gallate Supplementation on Inflammation, Iron Status, and Metabolomic Profiles in Women With Obesity: A Pilot Randomized Controlled Trial (2026) — Chronic inflammation
• 16 Randomized, controlled, double-blind clinical study evaluating the safety and efficacy of MD2011001 cream in mild-to-moderate atopic dermatitis (2016) — Grape seed extract (OPC)
• 17 Potential Benefits of Phytochemicals for Abdominal Aortic Aneurysm (2021) — Grape seed extract (OPC)
• 18 Grape seed and tea extracts and catechin 3-gallates are potent inhibitors of α-amylase and α-glucosidase activity (2012) — Grape seed extract (OPC)
• 19 A Randomized, Placebo-Controlled Study on the Safety and Efficacy of Daily Ingestion of Green Tea (<i>Camellia sinensis</i> L.) cv. "Yabukita" and "Suzuka" (2018) — Anthocyanins (berries)
• 20 The Effect of Antioxidant Polyphenol Supplementation on Cardiometabolic Risk Factors: A Systematic Review and Meta-Analysis (2024) — Anthocyanins (berries)
• 21 Immunomodulatory Effects of Aronia Juice Polyphenols—Results of a Randomised Placebo-Controlled Human Intervention Study and Cell Culture Experiments (2022) — Anthocyanins (Berries)
• 22 Potential of Polyphenols for Improving Sleep: Preliminary Results from a Review of Human Clinical Trials and Mechanistic Insights (2023) — Resveratrol
• 23 Phytochemicals in Cancer Prevention and Therapy: Truth or Dare? (2010) — Resveratrol
• 24 Polyphenolic Compounds from Red Grapes Acutely Improve Endothelial Function in Patients with Coronary Heart Disease (2005) — Resveratrol

5. Open Questions

• Dose-Response Relationship: Is there an optimal daily dose of catechins at which effects become detectable without compromising tolerability?
• Long-Term Effects: What are the impacts of multi-year catechin intake on inflammatory markers or cardiovascular endpoints?
• Interactions: How do catechins influence the effects of other micronutrients (e.g., iron, vitamin C) or medications (e.g., anticoagulants)?
• Microbiome: What role does the gut microbiome play in the activation or inactivation of catechins, and how can this be leveraged therapeutically?
• Target Groups: Are there differences in the efficacy of catechins across different age groups or in individuals with pre-existing metabolic conditions?
• Combination Therapies: Can catechins, in combination with other polyphenols, produce synergistic effects?
• Biomarkers: Which biomarkers are best suited for monitoring the effects of catechins in clinical practice?

See also the gaps list for all substances. This page is recalculated with each update.