Vitamin P (Flavonoids): Overview, Benefits, and More

Flavonoids or bioflavonoids (earlier known as vitamin P) are a vast group of yellow polyphenolic compounds that are naturally found in plant-based foods, such as deeply colored fruits, vegetables, tea, cocoa, and wine, commonly consumed in human diets.

There are more than 6,000 known flavonoids, which are responsible for:

• providing plants with color,
• aiding in growth,
• attracting insects for pollination, and
• protecting from ultraviolet rays, infection, and environmental stresses.

Flavonoids are nonessential nutrients that consist of two phenyl rings (A and B) and a heterocyclic ring C. The bioavailability, absorption, and excretion of flavonoids are largely dependent on the metabolism of the body.

Six types of flavonoids include:

1. Flavonols:
   • These are the most abundant source of flavonoids in the diet and include kaempferol, quercetin, myricetin, and fisetin. These are found in:
     • Lettuce
     • Tomatoes
     • Onions
     • Kale
     • Apples
     • Grapes
     • Berries
     • Tea
     • Red wine
2. Flavones:
   • They are widely present in foods, such as:
     • Parsley
     • Thyme
     • Mint
     • Celery
     • Chamomile
3. Flavanols or flavan-3-ols:
   • These include catechins, such as epicatechin and epigallocatechin, that are found in high concentrations in:
     • Black, green, and oolong tea
     • Bananas
     • Blueberries
     • Peaches
     • Pears
     • Cocoa 
     • Apples
     • Grapes
     • Red wine
4. Flavanones:
   • These are found in all citrus fruits and are responsible for the bitter taste of orange, lemon, and other citrus peels. 
   • Flavanones include hesperitin, naringenin, and eriodictyol.
5. Isoflavones:
   • Isoflavone compounds, such as genistin and daidzin, are found in legumes and soybeans.
6. Anthocyanins:
   • Anthocyanins, such as cyanidin, delphinidin, and peonidin, are responsible for the red, blue, or purple color of fruits and vegetables. These are found in:
     • Cranberries
     • Strawberries
     • Blueberries
     • Raspberries
     • Blackberries
     • Red grapes
     • Red wine

Studies report that vitamin P acts as an antioxidant, helps regulate the permeability of the blood capillaries, and protects against chronic diseases.

1. Has antioxidant effects:
   • Flavonoids reduce or neutralize the formation of reactive or unstable molecules called free radicals, which can lead to cell damage.
   • This damage can lead to inflammation and contribute to other problems, including cancer and heart disease.
2. Lowers the risk of chronic diseases:
   • Eating flavonoid-rich foods can help lower the risk of chronic diseases.
   • Studies report that preparations of vitamin P can elevate the low capillary resistance found in people subsisting on inadequate diets and patients with certain forms of purpura.
3. Prevents heart disease:
   • The antioxidant activity of flavonoids could help lower inflammation and blood pressure.
   • Flavanones help lower cholesterol levels in the body.
4. Prevents diabetes:
   • Daily intake of at least 300 mg of flavonoids improves the utilization of glucose and carbohydrates, in turn reducing the risk of diabetes by five percent.
5. Promotes brain health:
   • Flavonoids help protect the brain by lowering inflammation and protecting the vascular system. 
   • Studies have reported that flavanols, a type of flavonoids found in cocoa, could protect brain cells and boost brain health by improving brain function, memory, and blood flow to the brain.

Flavonoids, such as the catechins, are the most common group of polyphenolic compounds in the human diet and are found ubiquitously in plants, whereas flavonols, such as quercetin, are also found ubiquitously but in lesser quantities.

Foods with a high flavonoid content include:

• Parsley
• Onions
• Blueberries 
• Black tea, green tea, and oolong tee 
• Bananas 
• All citrus fruits
• Ginkgo biloba
• Red wine
• Sea-buckthorns
• Buckwheat
• Dark chocolate with a cocoa content of 70 percent or more

Early research on flavonoids is promising; however, it is still unclear if flavonoids are as essential for health as vitamins.

Nevertheless, a diet rich in healthy, whole foods, fruits, and vegetables that naturally contain flavonoids can contribute to overall good health.

At present, there is no dietary reference intake for flavonoids or standardized dose for flavonoid supplements.

Although there is no risk of toxicity from flavonoids commonly consumed through food, there may be risks associated with high-dose supplements, which may:

• negatively affect thyroid function,
• interact with medications, and
• affect levels of other nutrients in the body.