What Are Citrus Bioflavonoids?

You might think of vitamin C when it comes to citrus nutrition, but citrus fruits are also brimming with phytonutrients called bioflavonoids, and they’re definitely worth knowing about.

Key Takeaways

• Citrus bioflavonoids are antioxidant plant compounds found in the peel and pith of citrus fruits.¹
• Bioflavonoids work synergistically with vitamin C, delaying peak plasma levels up to an hour for a 35% increase in overall bioavailability.²
• Benefits include antioxidant protection, capillary/circulation support, and immune health.¹
• Key bioflavonoid compounds include hesperidin, rutin, quercetin, and naringin.
• Citrus bioflavonoids are available as individual supplements or in complex formulas.

Key Terms

• Bioflavonoid: antioxidant plant pigments that give citrus fruits their distinctive color or taste.
• Free radicals: highly unstable molecules with unpaired electrons. Formed during cell metabolism or immune activation.
• Antioxidant: substances that protect against oxidative stress caused by free radicals. Antioxidants neutralize free radicals by “lending” a spare electron.
• Hesperidin: bioflavonoid found in the white inner layer of grapefruit, orange, and lemon peels. Known for immune and cardio wellness.
• Rutin: bioflavonoid found in apples and citrus fruit. Known for cardiovascular health benefits.
• Quercetin: bioflavonoid found in citrus fruits, berries, apples, and green tea. Known for its immune and respiratory support.
• Naringin: bioflavonoid that gives grapefruit its bitter taste. Known for immune and antioxidant support.

What Are Citrus Bioflavonoids?

“Flavonoid” (or bioflavonoid) describes a group of plant-derived antioxidant phenolic substances used for pharmaceutical, supplemental, and even cosmetic benefits.³ Citrus bioflavonoids are found in fruits known to be rich in vitamin C.⁴

More Than Just Vitamin C

Discovered in 1936 by Nobel-prize winning scientist and research pioneer Albert Szent-Gyӧrgyi, bioflavonoids were originally called “vitamin P” (for their capillary permeability) and were noted as antioxidants that synergistically cooperate with vitamin C. ⁵ While they share antioxidant properties with vitamin C, citrus bioflavonoids are not the same substance.

Where Bioflavonoids Live in Citrus Fruits

Bioflavonoids in citrus fruits are concentrated in the peel and pith.⁴ The juice doesn’t contain the same levels of flavonoid nutrients, so supplementation may represent the best option for getting daily flavonoid support.

Key Citrus Bioflavonoids

Hesperidin

Hesperidin is naturally abundant in citrus fruits like oranges and lemons, most generally derived from the peel and pith after being processed for juice production. A flavonone (a subclass of flavonoids found in citrus fruits),⁶ hesperidin is associated with numerous health benefits including immune support and cardiovascular wellness. Studies have shown that supplementation with hesperidin may support healthy glucose response, blood lipid levels, and vascular function and blood flow.⁷ Hesperidin bolsters the antioxidant effects of vitamin C.

Rutin

Rutin is found in citrus peels and apple skins. Rutin is linked to promoting the natural production of nitric oxide for healthy blood flow and vascular wellness.⁸ It also contributes to enhanced capillary integrity.⁹ As an antioxidant, it can work alongside vitamin C to deliver powerful defense against free radicals.

Quercetin

Quercetin can be found in citrus fruits, apples, berries, and tea. A thoroughly researched bioflavonoid, quercetin has been linked to many aspects of immune health while also delivering strong antioxidant defense against free radicals.¹⁰ Quercetin is widely available as a standalone supplement but is sometimes combined with bromelain for enhanced absorption.

Naringin

Naringin and its derivatives can be found in a number of foods, including grapefruit, tart cherries, and sour orange. As with other flavonoids, naringin has been studied for its potent antioxidant and immune health support,¹¹ but it’s recommended that you speak with your doctor before taking naringin if you take prescription medications. This is because bioflavonoids derived from grapefruit may interact with certain pharmaceuticals.¹²

Health Benefits of Citrus Bioflavonoids 

Antioxidant Protection

Citrus bioflavonoids are well known for their antioxidant properties, a benefit that’s enhanced as they work synergistically alongside vitamin C.¹³ Research indicates that flavonoids support the activity of antioxidant enzymes—defending against free radicals and reducing exercise-induced inflammation.¹³

Capillary and Vascular Support

The antioxidant properties of bioflavonoids can also support vascular health, with hesperidin in particular linked to improved capillary integrity.⁷ Flavonoids are known to defend against oxidative stress that reduces the bioavailability of nitric oxide (NO) in the body. This contributes to normalized NO levels, healthier blood flow, and vascular function.¹⁴ Additionally, flavonoids are linked to promoting healthy vascular tone,¹⁴ an important factor in long-term wellness.

Immune System Support

Citrus bioflavonoids support immune health through their antioxidant activity and by working synergistically with vitamin C.¹³ In fact, bioflavonoids can delay peak plasma levels of vitamin C for up to an hour for a 35% increase in overall bioavailability.² The result? Vitamin C has more time to support immune health and diminish potential damage from free radicals produced during immune activation. This role in supporting cellular defense mechanisms makes citrus bioflavonoids a natural complement to vitamin C supplementation.

Food Sources of Citrus Bioflavonoids

Citrus bioflavonoids can be found in citrus fruits, in addition to apples, berries, and some beverages like tea or even coffee, depending on the specific type of flavonoid. Because they tend to be concentrated primarily in the peel and pith of the fruit, getting sufficient bioflavonoids from diet alone can be challenging. For standardized and consistent amounts, supplementation offers a convenient and consistent way to make sure you’re benefiting from these potent compounds every day.

How to Supplement with Citrus Bioflavonoids

Always follow the dosage directions on your product label unless your doctor has specified otherwise. Although the optimum daily citrus bioflavonoid intake hasn’t been determined, some supplement advocates recommend approximately 1,000 to 6,000 mg daily for adults.¹⁵

Individual vs. Complex Formulas

Many citrus bioflavonoids are conveniently available in either individual supplements, as a citrus bioflavonoid complex, or in a combination formula with vitamin C. Compounds commonly featured in citrus bioflavonoid supplements include hesperidin, rutin, naringin, and quercetin.

Individual bioflavonoid supplements allow you to focus on a specific benefit, while a complex supplement can deliver the broader antioxidant and immune support benefits of each type.

Citrus Bioflavonoids and Vitamin C

Citrus bioflavonoids are naturally found together with vitamin C in many foods, and this makes sense considering the way these two nutrients work together. Both offer powerful antioxidant support, and flavonoids can help enhance the benefits of vitamin C by prolonging its time in the body.²

To learn more about vitamin C, check out Benefits of Vitamin C and the Best Vitamin C Supplements to Try.

Frequently Asked Questions

• What are citrus bioflavonoids?
  Plant compounds found in citrus fruits (primarily in the peel and pith) that act as antioxidants and work synergistically with vitamin C.¹ Key citrus bioflavonoids include hesperidin, rutin, quercetin and naringin.
• Are citrus bioflavonoids the same as vitamin C?
  No, they’re distinct compounds that often occur together in citrus fruits. Vitamin C is a water-soluble vitamin; bioflavonoids are a separate class of plant polyphenols. Recent studies have highlighted a promising synergistic interaction between flavonoids and vitamin C: flavonoids enhance the stability, recycling, and intestinal absorption of vitamin C, while vitamin C complements the antioxidant capacity and cellular bioactivity of flavonoids.¹⁶
• What are citrus bioflavonoids used for?
  Primarily used as antioxidant support in combination with vitamin C, for capillary and circulatory support, and as part of immune support routines.^13,14 Individual compounds like hesperidin are also studied for cardiovascular wellness.⁷
• Are citrus bioflavonoids antioxidants?
  Yes, they’re potent antioxidants. They help neutralize free radicals and work synergistically with vitamin C to complement antioxidant activity in the body.¹³ This cooperation involves promoting vitamin C’s absorption and stabilizing its duration in the body while the vitamin enhances the antioxidant and bioactivity of the flavonoids.¹⁶
• Where can citrus bioflavonoids be found naturally?
  Primarily in the peel and pith of citrus fruits. Because they’re concentrated in the pith rather than the juice, eating whole fruit delivers more bioflavonoids than drinking juice. Concentrated supplemental forms are available for consistent, higher-dose intake.

Conclusion

Citrus bioflavonoids offer excellent antioxidant defense and a potent way to bolster the benefits of vitamin C. While they’re present in a variety of delicious fruits, it can be a challenge to get enough from diet alone. For a boost to your immune and cardiovascular health, be sure to check out Swanson’s science-backed line of bioflavonoid supplements.

About Lindsey Toth, MS, RD

Lindsey is a nationally-recognized registered dietitian and nutritionist with a soft spot for pie. She empowers people to take charge of their health by finding the balance between the pleasure and nourishment in food. Her philosophy is that you should take care of your body because it’s the only permanent home you have. It’s what inspired her to pursue a career in nutrition. 

These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.

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