What Are Polyphenols?

What are polyphenols? What are their health benefits? And what foods contain them? 
Written by Elise Goldsworthy
Bachelor of Health Science (NUTRITIONAL MEDICINE)
January 25, 2022

For me, utilising polyphenols for your health is truly using food as medicine. This is where everyday foods like garlic, nuts, broccoli, flaxseeds, blueberries and green tea really shine. Let’s take a look at what polyphenols are and how to reap their health benefits. 

What Are Polyphenols?

Polyphenols are also known as Phytochemicals (plant chemicals). Polyphenols are a class of compounds found in plants, nuts and seeds. The term polyphenol is often used to describe specific compounds that influence human health. They are not essential nutrients like vitamins and minerals, yet their benefits on various aspects of our health are quite remarkable. 

There are more than 8000 polyphenol compounds identified in the scientific literature. Overall, epidemiologic studies reveal that dietary polyphenols are associated with lower chronic disease development. 

Polyphenols are an abundant source of antioxidant compounds. Consuming polyphenols helps reduce the risk of inflammatory diseases, including cancer, diabetes and heart disease. 

Polyphenol containing vegetables in the colour of the rainbow

Common Polyphenols And Food Sources:

Alkaloids

  • Caffeine (coffee)
  • Trigonelline (coffee)

Carotenoids

  • Alpha-carotene (carrots, pumpkin, orange)
  • Beta-carotene (dark green leafy vegetables, pumpkin)
  • Lutein (spinach, pawpaw, broccoli, rhubarb, plum)
  • Zeaxanthin (spinach, kale, eggs)
  • Lycopene (tomatoes, grapefruit, apricots)

Flavonoids

Flavones 

  • Apigenin - (parsley, celery, camomile)
  • Luteolin - (broccoli, artichoke, camomile)

Flavanones

  • Hesperetin, Naringenin (grapefruit)

Anthocyanidins

  • Cyanidins (blueberry, cherry, elderberry)

Isoflavones

  • Genistein, Daidzein (soy, legumes)

Flavan-3-ols

  • Catechin, Epigallocatechins (green tea, cocoa)

Flavonols

  • Quercetin (onion, kale, citrus)
  • Kaempferol (spinach) 
  • Myricetin (tomatoes, nuts)

Hydroxycinnamic acids

  • Caffeic Acid (artichoke, apple, olive oil)
  • Curcumin (turmeric)

Indoles

  • Indole-3-carbinol (Broccoli, kale, brussels sprouts)

Lignans

  • Phytoestrogens (flax, sesame, peptas, sunflower seeds)

Organosulfur Compounds

  • Alliin (garlic)
  • Allicin (garlic)
  • Sulforaphane (Broccoli sprouts, kale)
  • Allyl isothiocyanate (mustard, wasabi)

Phytosterols

  • Sitosterol (almonds, cashews, peanuts, avocado)
  • Campesterol (buckwheat)

Stilbenes

  • Resveratrol (peanuts, grapes)

Tannins

  • Proanthocyanidins (tea, blueberry, elderberry)

Image credit: Linus Pauling Institute 

5 Polyphenols For Your Health

Green tea - Polyphenols

Epigallocatechin Gallate

Epigallocatechin gallate (EGCG) is the major polyphenol found in green tea. EGCG has a wealth of research supporting its anti-cancer and cardiovascular properties. EGCG is the most widely studied chemical compound of the flavanol class of polyphenols. Other food sources of EGCG include cocoa, broad beans and prune juice. Pervin et al. (2019) established beneficial effects on cognitive function by green tea consumption. Another interesting quality of EGCG is the epigenetic effects it has on reducing cancer cell formation. Research shows EGCG has tumour-suppressing properties at a DNA level, making this polyphenol valuable in cancer prevention. 

Health Benefits of EGCG

  • Anti-cancer
  • Anti-angiogenic
  • Anti-inflammatory
  • Neuroprotective

Tumeric - Polyphenols

Curcumin

Curcumin is the active compound found in turmeric. Curcumin has been used therapeutically across ancient cultures for centuries. Modern research supports the medicinal properties of turmeric and the curcuminoids found within. Curcumin may also be a useful additive therapy in skin disorders. 

A study published by Hanai et al. (2006) in Clinical Gastroenterology and Hepatology, found that curcumin improves ulcerative colitis symptoms. In this double-blind multicentre study, one study group received 2g of curcumin per day.. At the end of the study period, curcumin appeared to be a safe therapeutic intervention for maintaining remission in patients with inflammatory bowel disease. 

Health Benefits of Curcumin

  • Anti-inflammatory
  • Analgesic
  • Antioxidant
  • Anti-cancer
  • Neuroprotective

Quercetin

Quercetin is a polyphenol from the flavonoid class of phytochemicals. Quercetin is present in most plant foods and boasts therapeutic actions in the body. It is a potent antioxidant agent, which may protect against the development of cancer, diabetes and chronic diseases. Research suggests quercetin helps maintain healthy blood-glucose levels due to the effect on pancreatic function. Quercetin helps promote insulin secretion and improves glucose utilisation in body tissues. 

Quercetin has the ability to target cancer cells, causing programmed cell death (apoptosis), according to Reyes-Farias et al. (2019). Quercetin also demonstrates positive cardiovascular effects as well. In a recent study, quercetin reduced peripheral vascular resistance and altered electrolyte levels in the kidney, thereby reducing blood pressure. 

Health Benefits of Quercetin

  • Anti-diabetic
  • Anti-inflammatory
  • Cardioprotective
  • Anti-cancer
  • Regulates blood pressure

Peanuts - Polyphenols

Resveratrol

Notoriously associated with red wine consumption, resveratrol gained popularity as a cardioprotective polyphenol during the early 1990’s. During this time, a hypothesis known as the ‘French Paradox’ was explored. It was thought that moderate red wine consumption accounted for low incidences of heart disease in French populations, where high saturated fat foods were commonly consumed. 

Don’t like red wine? Well, resveratrol is also naturally found in peanuts and berries. In fact, roasting peanuts appears to augment resveratrol’s biologic activity in the body. Good news for peanut fans!

Resveratrol also possesses anticancer and neuroprotective activities as shown in numerous studies. Resveratrol was found to reduce brain inflammation and aid the clearance of beta-amyloid plaques and subsequent Alzheimer’s disease in vivo studies. 

Health Benefits of Resveratrol

  • Cardioprotective
  • Improves Alzheimer’s symptoms
  • Anti-inflammatory
  • Anti-aging properties

Cabbage, broccoli and brussel sprouts - Polyphenols

Sulforaphane

Sulforaphane is a personal favourite polyphenol. Sulforaphane studies have been illuminated by one of my molecular biology and research idols, Dr. Rhonda Patrick. Sulforaphane is an organosulfur compound and is found in broccoli, Brussels sprouts, cabbage and kale. Sulforaphane is highly concentrated and most bioavailable in broccoli sprouts. Sulforaphane modulates the expression of pro-inflammatory cell pathways and possesses anti-cancer properties. Sulforaphane ameliorates Alzheimer’s Disease symptoms according to research published in the International Journal of Molecular Sciences.

Health Benefits of Sulforaphane

  • Anti-cancer
  • Relieves Alzheimer’s symptoms
  • Neuroprotective
  • Liver detoxification
  • Anti-inflammatory

Article References

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Chaplin, A., Carpéné, C., & Mercader, J. (2018). Resveratrol, Metabolic Syndrome, and Gut Microbiota. Nutrients, 10(11), 1651. https://doi.org/10.3390/nu10111651

Cione, E., La Torre, C., Cannataro, R., Caroleo, M. C., Plastina, P., & Gallelli, L. (2019). Quercetin, Epigallocatechin Gallate, Curcumin, and Resveratrol: From Dietary Sources to Human MicroRNA Modulation. Molecules (Basel, Switzerland), 25(1), 63. https://doi.org/10.3390/molecules25010063

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