As discussed in the earlier post about carotenoids (the first of our ‘Eat the Rainbow’ series), ‘phytonutrients’ are plant-derived pigments. These pigments give vibrant colours and attractive fragrances to plants – and are also great for our health! That’s why we’re encouraged to “eat the rainbow”, and get the benefits of all the different types of phytonutrients out there.
Here’s introducing a group of phytonutrients that’s the most ubiquitious of them all: flavonoids.
With over 9000 members, it’s one of the largest nutrient families known to scientists.1, 2 Here’s where you can find them.
“Flavonoids” stems from the Latin word “flavus,” which means yellow, because these plant pigments are seen most notably in yellow plants. However, different types of flavonoids are found in several other sources:3, 4
i. A colourless group called flavanols or flavan-3-ols (eg catechins):
These are found in apples, red wine and tea – although green tea contains a higher amount of flavanols than black tea.5
ii. Colourless to pale yellow pigments called flavanones:
Found in citrus fruits, grapefruits, lemons, and oranges.
iii. Colourless to pale yellow and yellow-green pigments called flavonols and flavones:
Found in onions, almonds, buckwheat, and also in leek, cherry, tomato skin, broccoli, kale, parsley, celery, capsicum peppers, and red and white wines.
iv. Shades of beige, tan, red, brown to black pigments called proanthocyanidins:
Found in beans, seeds, apples, cinnamon, grape seed, cocoa and the grapes used to make wines. (That’s right – your wine is brimming with flavonoids!)
v. Red, purple and blue pigments called anthocyanidins:
Found in raspberries, blueberries, blackcurrants, cherries, eggplant peel, black rice and red cabbage.
As you can see, this large group of pigments starts off colourless but eventually takes over what seems like the entire colour wheel!
Each of these types of flavonoids offers powerful health benefits. Flavonols, for instance, are known for their strong anti-bacterial (bacteria fighting) properties, amongst others. Here’s a look at the health benefits of flavonoids in general –
Flavonoids as Antioxidants
Many flavones and flavonols absorb UV radiation to protect us from free radical damage from the sun.2
Their antioxidant activity also prevents the formation of allergies and other problems caused by unnecessary activation of the immune system (excessive inflammation).
Recent studies have even shown that flavonoids are involved in the transport of vitamin C (which is a powerful antioxidant itself) as well as the enzyme that converts vitamin C into its other forms.6
Flavonoids and Diabetes
A flavanol called quercetin is believed to help the body regenerate islet cells, which produce the hormone ‘insulin’ in the pancreas. This is useful for type-I diabetes, where islet cells are destroyed.
Interestingly, flavonoids form special UV patterns on flowers called “nectar guides”, which are visible to bees but not humans.7 This may be how flavonoids make their way into honey, which is believed to provide beneficial effects on body weight and blood lipids of diabetic patients.8, 9
Flavonoids in Heart Disease and Cancer
Heard that red wine is good for your heart? Here’s how it (along with other sources of flavanoids) can affect heart disease:1, 4, 10-12
Flavonoids are known to reduce the pressure on blood vessel walls, thereby preventing hypertension and heart diseases like atherosclerosis.
Free radical interaction with LDL (bad cholesterol) is thought to be an early event in atherosclerosis. Flavonoids can avoid this by neutralizing the free radicals via their antioxidant activity.
Through its antioxidant properties, flavonoids can inhibit the formation of cancer and, according to some studies, limit cancer growth. The exact mechanism is unclear – but it’s believed that flavonoids stop cancer cells from growing their own blood vessels, so these cancer cells die off due to lack of nutrition.
Flavonoids in our Diet
Given all these health benefits, it is no wonder that many Ayurvedic preparations (like triphala and kumbhi) are rich in flavonoids.13, 14
While there’s no specific daily value, it is recommended that we get a good mix of flavonoids from different sources to avail of all its potential benefits.15
A variety of colours will put you well on the path to getting enough flavonoids, so go on and fill your food with these healthy, natural pigments!
1. Xiao ZP, et al. Mini Rev Med Chem 2011, 11(2): 169-177.
2. Pandey KB & Rizvi SI. Oxidative Medicine and Cellular Longevity 2009, 2(5): 270-278.
3. Grotewold E. The Science of Flavonoids. Springer, 2007.
4. Kumar S & Pandey AK. Chemistry and Biological Activities of Flavonoids: An Overview, vol. 2013, 2013.
5. Chatterjee P, et al. Journal of Advanced Pharmaceutical Technology & Research 2012, 3(2): 136-138.
6. Song J, et al. J Biol Chem 2002, 277(18): 15252-15260.
7. Thompson WR, et al. Science 1972, 177(4048): 528-530.
8. Bahrami M, et al. Int J Food Sci Nutr 2009, 60(7): 618-626.
9. Al-Waili NS. J Med Food 2004, 7(1): 100-107.
10. Nijveldt RJ, et al. Am J Clin Nutr 2001, 74(4): 418-425.
11. Shi J, et al. J Med Food 2003, 6(4): 291-299.
12. Tapas AR, et al. Tropical Journal of Pharmaceutical Research 2008, 7(3): 1089-1099.
13. Gupta M. Int J Pharma Bio Sci 2010: 1-13.
14. Kumar S, et al. International Journal of Pharmaceutical Sciences Review and Research 2011, 8(1): 70-74.
15. Haytowitz DB, et al. Sources of Flavonoids in the U.S. Diet Using USDA’s Updated Database on the Flavonoid Content of Selected Foods. Beltsville, MD, USA: U.S. Department of Agriculture (USDA); 2006.