Understanding the Terminology: From Bioflavonoids to Flavonoids
For anyone researching plant-based nutrients, the terms “bioflavonoids” and “flavonoids” are often used interchangeably. The primary and most scientifically accepted term in modern usage is 'flavonoids'. Bioflavonoids can be considered a subset of the larger group of polyphenolic compounds, but in most health and nutrition contexts, referring to them as flavonoids is the standard practice. Flavonoids are the colorful pigments found in fruits, vegetables, flowers, and herbs, which offer a range of health benefits to humans, including powerful antioxidant and anti-inflammatory effects. Their presence is responsible for the vibrant red, yellow, and blue hues seen in many plant foods, from blueberries to dark chocolate. The name "flavonoid" is derived from the Latin word flavus, meaning yellow, a nod to the color of the first isolated compounds.
The Historical 'Vitamin P' Designation
In the 1930s, Nobel Prize-winning scientist Albert Szent-Györgyi discovered a group of compounds in citrus fruits that he found supported vascular health and capillary permeability. He initially thought these were a new class of vitamins and so he named them “vitamin P,” with 'P' standing for permeability. The substances he identified included hesperidin and rutin. However, subsequent research showed that bioflavonoids are not essential nutrients in the same way that true vitamins are, and the term “vitamin P” eventually fell out of scientific use by the 1980s. While the name is now obsolete in formal scientific discourse, it sometimes resurfaces in older literature or supplement advertising to highlight the nutritional value of these compounds.
Major Subgroups of Flavonoids
Flavonoids are a diverse class of phytochemicals, with over 8,000 different types identified. They are categorized into several major subgroups based on their chemical structure. Each subgroup is found in different food sources and offers a unique spectrum of health benefits.
- Flavonols: These are the most common flavonoids in the human diet and are found in onions, kale, apples, and berries. Quercetin is a well-known flavonol with notable anti-inflammatory and anti-allergic effects.
- Flavanones: Primarily found in citrus fruits like oranges, lemons, and grapefruits, flavanones are responsible for their characteristically bitter taste. Examples include hesperidin and naringenin, which are recognized for their cardiovascular and antioxidant properties.
- Anthocyanins: These flavonoids are responsible for the red, purple, and blue pigments in berries, grapes, and red cabbage. Cyanidin and malvidin are examples that possess powerful antioxidant properties and support cognitive function.
- Isoflavones: With estrogen-like activity, isoflavones are primarily concentrated in soy products and other legumes. Genistein and daidzein are the most well-known isoflavones, studied for their potential effects on hormonal balance and cancer prevention.
- Flavan-3-ols (Catechins): Prominently found in green tea, black tea, and cocoa products, catechins are potent antioxidants. Epigallocatechin gallate (EGCG) is a particularly well-researched catechin from green tea.
Bioflavonoid vs. Vitamin: A Comparison
Despite the historical “vitamin P” label, flavonoids are not considered true vitamins in a nutritional context. They are beneficial but not essential for basic bodily functions like vitamins are.
| Feature | Bioflavonoids (Flavonoids) | True Vitamins (e.g., Vitamin C) |
|---|---|---|
| Essentiality | Not strictly essential for survival; the body does not have recognized deficiency symptoms. | Absolutely essential for normal metabolism and body functions; deficiency leads to specific health issues (e.g., scurvy for Vitamin C). |
| Recommended Intake | No official recommended daily allowance (RDA) established. | Have an established RDA or recommended daily intake (e.g., 90 mg/day for Vitamin C for adult men). |
| Biological Role | Act as antioxidants, anti-inflammatories, and complement the action of other nutrients like Vitamin C. | Act as coenzymes or vital components in metabolic processes. |
| Source | Produced by plants for their own protection, color, and growth regulation. | Both plant and animal sources; must be consumed via diet or supplements. |
Health Benefits and Synergy with Other Nutrients
Research has extensively explored the health benefits of flavonoids, largely attributing them to their powerful antioxidant and anti-inflammatory properties. By neutralizing free radicals, they help reduce oxidative stress, which is linked to various chronic diseases such as cancer and heart disease. Some studies suggest that diets rich in flavonoid-containing foods can contribute to a lower risk of certain cancers, cardiovascular disease, and improved cognitive function. Furthermore, flavonoids are known to work synergistically with other nutrients, particularly Vitamin C. They help protect Vitamin C from oxidation, thereby enhancing its absorption and overall activity in the body. This cooperative effect is why bioflavonoids are often included alongside Vitamin C in dietary supplements.
Food Sources for a Bioflavonoid-Rich Diet
Consuming a variety of colorful plant-based foods is the most effective way to ensure a broad intake of different flavonoid types.
- Berries: Blueberries, strawberries, and blackberries are rich in anthocyanins.
- Citrus Fruits: Oranges, lemons, and grapefruits contain high levels of flavanones like hesperidin and naringenin.
- Tea: Both green and black tea are excellent sources of catechins.
- Cocoa and Dark Chocolate: Flavonoids like catechins are found in high-quality cocoa.
- Onions and Kale: These vegetables are particularly rich in the flavonol quercetin.
- Legumes: Soybeans and soy products are significant sources of isoflavones.
- Red Wine: Grapes and red wine contain anthocyanins and other polyphenols.
- Herbs and Spices: Parsley, thyme, and celery contain flavones.
Conclusion
The term "bioflavonoids" is most accurately and commonly known as "flavonoids," and refers to a vast group of health-promoting plant compounds. While historically and briefly designated as the non-essential "vitamin P," their beneficial properties as powerful antioxidants and anti-inflammatories are well-established. By consuming a diverse diet rich in colorful fruits, vegetables, teas, and other plant foods, individuals can easily increase their intake of these valuable phytochemicals and leverage their protective and synergistic effects within the body. Read more on flavonoid subgroups from the Linus Pauling Institute at Oregon State University.
