What Are Flavanoids?
My recent post about cocoa flavonoids got me started on the question of the differences between flavonoids, flavanoids, and flavanols. These all tend to get lumped together, but my inner nerd demands we develop the distinction.
What Are Flavanoids?
Flavanoids are a subclass of the antioxidant compounds known as flavonoids. More broadly called plant polyphenols, these compounds all share a common chemical backbone, with flavanoids being distinguished from their parent compounds by the lack of a double bond in the furan (oxygen-containing) ring. Subclasses of the flavanoids are known as flavan-3-ols, flavan-4-ols, and flavanones. These compounds are all separated by the location of hydroxyl groups, or in the latter case a ketone group, around the furan ring. Enough chemistry.
Flavanoids are secondary plant metabolites, which means they aren’t essential to the growth and development of the plant. Having said that though , flavanoids serve many functions in plant growth, and are often times produced in response to stress, or to provide protection from outside threats like fungus or insects, which may help explain the bitter taste frequently associated with flavanoids.
Nutritionally, flavanoids were once considered antinutrients, as the polyphenol structure is a metal chelator, and therefore capable of binding iron and facilitating its removal from the body. However, research over the last 30-years has turned the tide, as evidence mounts in favor of flavanoids. Newer research has shown flavanoids may function as antioxidants, anticancer agents, and antimicrobials. Some research suggests they may also help regulate blood sugar, or could act to improve cardiovascular function. Although the benefits of these compounds is by no means clear, there’s little doubt that interest in their possible health benefits is gaining a great deal of attention.
Classes of flavanoids, and some of their compounds includes the following:
FLAVANONES: Hesperetin, Naringenin, Eriodictyol
FLAVAN-3-OLS: (+)-Catechin, (+)-Gallocatechin, (-)-Epicatechin, (-)-Epigallocatechin, (-)-Epicatechin-3-gallate, (-)-Epigallocatechin 3-gallate, (-)-Epigallocatechin 3-gallate, Theaflavin, Theaflavin 3-gallate, Theaflavin 3′-gallate, Theaflavin 3,3′ digallate, Thearubigins
FLAVAN-4-OLS: Apiforol, Luteoforol
FLAVAN-3,4-DIOLS: Leucoanthycyanidins
Of these, the most commonly occurring flavanoids in nature are catechin, epichatechin, and their derivates. When we talk about antioxidants in green tea and cocoa, these are the compounds that are being referenced. For the purposes of this discussion, we’ll focus on a handful of the flavanones and flavan-3-ols, as much of the current research is directed at these two classes of compounds.
The following table is a list of how much of the level of flavanoids in many common foods.
Average Level of Flavanoids In Select Foods (mg/100-gram serving)
| Food | Hesperetin | Naringenin | Catechin | Epicatechin | Epigallocatechin | Epigallocatechin 3-gallate | Thearubigins |
|---|---|---|---|---|---|---|---|
| Red Table Wine | -- | -- | 7.6 | 4.3 | -- | -- | -- |
| White Table Wine | -- | -- | 0.8 | 0.6 | -- | -- | -- |
| Raw Apples (with skin) | -- | -- | 0.9 | 8.1 | -- | -- | -- |
| Blackberries | -- | -- | 0.7 | 18.1 | -- | -- | -- |
| Blueberries (raw) | -- | -- | 0 | 1.1 | -- | -- | -- |
| Dark Chocolate | -- | -- | 12.0 | 41.5 | -- | -- | -- |
| Milk Chocolate | -- | -- | 2.9 | 10.5 | -- | -- | -- |
| Grapefruit (raw) | 1.5 | 53 | -- | -- | -- | -- | -- |
| Black Grape Juice | -- | -- | 0.8 | 0 | -- | -- | -- |
| Lemon Juice (raw) | 12.0 | 1.4 | -- | -- | -- | -- | -- |
| Orange (raw) | 32.7 | 11.2 | -- | -- | -- | -- | -- |
| Tangelo (raw) | 74.9 | 42.5 | -- | -- | -- | -- | -- |
| Black Tea (brewed) | -- | -- | 1.5 | 2.3 | 10.4 | 11.5 | 73.4 |
| Blac Tea Leaves (dry) | -- | -- | 162.3 | 240.3 | 1116.1 | 1199.4 | 5918.9 |
| Green Tea (brewed) | -- | -- | 2.7 | 8.5 | 17.1 | 82.9 | 1.1 |
| Green Tea Leaves (dry) | -- | -- | 33.0 | 791.5 | 1695 | 1701.6 | 131.9 |
| Oolong Tea (brewed) | -- | -- | 0.23 | 2.6 | 6.7 | 36.0 | -- |
| Oolong Tea Leaves (dry) | -- | -- | 23.9 | 259.5 | 600.5 | 3602 | -- |
Interestingly enough, according to the USDA report, levels of flavanoids in many colored fruits and vegetables are, on average, quite low. Foods with low levels of flavanoids include most vegetables, tomatoes, and bananas. This makes sense, since flavanoids tend to be associated with bitter taste, and bright colors in fruits. So, if you’re looking to increase your consumption of flavanoids, you can see that teas and bitter fruits tend to be the “go-to” foods.
Sources
USDA Table Of Flavonoid Content
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