Polyphenols

What it is and what it does

• Polyphenols are plant compounds with very varied structures, each carrying one or more phenolic groups. (ICMR-NIN. Indian Food Composition Tables 2017 (Longvah T et al.))
• Flavonoids are one large family of polyphenols found in plants. (Linus Pauling Institute Micronutrient Information Center, Oregon State University. Flavonoids (written 2005 by J. Higdon; updated November 2015 by B. Delage; reviewed February 2016 by A. Crozier))
• Over 500 different polyphenol molecules are known to be present in foods. (ICMR-NIN. Indian Food Composition Tables 2017 (Longvah T et al.))
• As a chemical property, phenolic compounds show antioxidant activity: they scavenge reactive oxygen species, act as reducing agents and/or bind (chelate) iron ions. (Samtiya M, Aluko RE, Dhewa T (2020). Plant food anti-nutritional factors and their reduction strategies: an overview. Food Production, Processing and Nutrition 2:6 (peer-reviewed review; open access, CC BY 4.0) (DOI 10.1186/s43014-020-0020-5))
• Certain polyphenols in plant foods such as cereals and pulses lower the absorption of non-haem iron (the form of iron in plant foods). (NIH Office of Dietary Supplements. Iron Fact Sheet for Health Professionals (updated 2025-09-04))
• How flavonoids are digested, absorbed and changed in the body depends on their chemical properties. (Linus Pauling Institute Micronutrient Information Center, Oregon State University. Flavonoids (written 2005 by J. Higdon; updated November 2015 by B. Delage; reviewed February 2016 by A. Crozier))

Why it matters

• People take in around 1 g of polyphenols a day, mostly from plant foods. (Abioye VF, Babarinde GO, Ogunlakin GO, Adejuyitan JA, Olatunde SJ, Abioye AO (2022). Varietal and processing influence on nutritional and phytochemical properties of finger millet: A review. Heliyon 8(12):e12310 (peer-reviewed review; PMC9800331; open access) (DOI 10.1016/j.heliyon.2022.e12310))
• High intakes of flavonoids from food are generally regarded as safe, partly because the body absorbs little of them. (Linus Pauling Institute Micronutrient Information Center, Oregon State University. Flavonoids (written 2005 by J. Higdon; updated November 2015 by B. Delage; reviewed February 2016 by A. Crozier))
• Flavonoid supplements (not foods) may interfere with blood-thinning medicines and can increase the toxicity of many drugs taken at the same time. (Linus Pauling Institute Micronutrient Information Center, Oregon State University. Flavonoids (written 2005 by J. Higdon; updated November 2015 by B. Delage; reviewed February 2016 by A. Crozier))

General information, not medical advice — for your own needs, ask a doctor or dietitian.

How much is needed

India’s own figure (ICMR-NIN 2020) comes first. Figures from other bodies are shown only where they help, and say whose they are.

Sources: ICMR-NIN Expert Group. Short Report of Nutrient Requirements for Indians: Recommended Dietary Allowances and Estimated Average Requirements - 2020

Absorption and food

• Because the polyphenols sit mostly in the bran, whole finger millet flour has more of them than sieved flour. (Abioye VF, Babarinde GO, Ogunlakin GO, Adejuyitan JA, Olatunde SJ, Abioye AO (2022). Varietal and processing influence on nutritional and phytochemical properties of finger millet: A review. Heliyon 8(12):e12310 (peer-reviewed review; PMC9800331; open access) (DOI 10.1016/j.heliyon.2022.e12310))
• In one study, sprouting or pressure-boiling finger millet reduced its total polyphenols by about 50%. (Abioye VF, Babarinde GO, Ogunlakin GO, Adejuyitan JA, Olatunde SJ, Abioye AO (2022). Varietal and processing influence on nutritional and phytochemical properties of finger millet: A review. Heliyon 8(12):e12310 (peer-reviewed review; PMC9800331; open access) (DOI 10.1016/j.heliyon.2022.e12310))
• Pearling (abrading) quinoa to remove saponins also removed part of its phenolic compounds: 21.5% of the free and 35.2% of the bound phenolics in one study. (El Hazzam K, Hafsa J, Sobeh M, Mhada M, Taourirte M, El Kacimi K, Yasri A (2020). An Insight into Saponins from Quinoa (Chenopodium quinoa Willd): A Review. Molecules 25(5):1059 (peer-reviewed review; PMC7179108; CC BY) (DOI 10.3390/molecules25051059))
• ICMR-NIN states that steaming is the best cooking method to increase the level of polyphenols in vegetables and greens. (ICMR-NIN. Dietary Guidelines for Indians 2024)
• The flavonoid content of foods varies with farming practices, growing conditions, ripening, storage and processing. (Linus Pauling Institute Micronutrient Information Center, Oregon State University. Flavonoids (written 2005 by J. Higdon; updated November 2015 by B. Delage; reviewed February 2016 by A. Crozier))
• ICMR-NIN lists flavonoids and phenolics among the plant compounds present in vegetables. (ICMR-NIN. Dietary Guidelines for Indians 2024)
• In grains such as finger millet, polyphenols are more concentrated in the bran (aleurone layer, seed coat and pericarp) than in the rest of the grain. (Abioye VF, Babarinde GO, Ogunlakin GO, Adejuyitan JA, Olatunde SJ, Abioye AO (2022). Varietal and processing influence on nutritional and phytochemical properties of finger millet: A review. Heliyon 8(12):e12310 (peer-reviewed review; PMC9800331; open access) (DOI 10.1016/j.heliyon.2022.e12310))
• Brown finger millet varieties contain about 1.2-2.3% polyphenols, white varieties about 0.3-0.5%. (Abioye VF, Babarinde GO, Ogunlakin GO, Adejuyitan JA, Olatunde SJ, Abioye AO (2022). Varietal and processing influence on nutritional and phytochemical properties of finger millet: A review. Heliyon 8(12):e12310 (peer-reviewed review; PMC9800331; open access) (DOI 10.1016/j.heliyon.2022.e12310))