Grow Youthful: How to Slow Your Aging and Enjoy Extraordinary Health
Grow Youthful: How to Slow Your Aging and Enjoy Extraordinary Health

Citrus fruit bioflavonoids

What are citrus bioflavonoids?

Benefits and uses of citrus bioflavonoids

Vitamin C supplementation?


What are citrus bioflavonoids (flavonoids)?

Citrus fruits are well known for being a good source of vitamin C. The reason is that the flavonoids they contain greatly enhance and prolong the effect of the vitamin C.

Most vitamin C supplements are made from synthetic ascorbic acid manufactured in China. This form of vitamin C is less effective on its own or in the form of a tablet. Without the natural flavonoids found in citrus (and some other fruits and vegetables), ascorbic acid is easily oxidized and can actually harm your body. This is why I emphasise throughout Grow Youthful that whole food nutrition is so much better than synthetic supplements.

Citrus fruits such as lemons, limes, grapefruits, oranges and tangerines contain many other nutrients that enhance the effects of vitamin C as well as being powerful antioxidants. The most potent of these citrus nutrients are a group of bioactive flavonoids also known as vitamin P. They include diosmetin, diosmin, hesperidin, naringin, narirutin, neohesperidin, nobiletin, quercetin, rutin and the flavone tangeritin. They are essential for the proper absorption of Vitamin C, and studies have shown that they enhance and prolong the action of vitamin C.

Interestingly, these flavonoid levels are highest in ripe, fresh-picked fruit. If they were picked unripe, or they have been in storage, their health benefits will be lower. The antioxidant content decreases within days. Nutrients are found in the whole fruit, including the pith, rind (peel) and pips/seeds. The white pith is especially valuable. Do not throw away a lemon that you have squeezed - the pulp and the rind or peel are rich in nutrients. If the peel is organic, you can shred it into a lemon zest and use it in all sorts of dishes - cook it in cakes, desserts, with meats. Add it to salads. Put it through your juicer.

Now you can see why supermarket orange juice is of virtually no benefit. It is high in sugar (mostly fructose, the sugar that causes obesity), has all the beneficial pulp, seeds and rind removed, and is weeks, months or sometimes even years old (most of the beneficial flavonoids have long gone).

Cocoa is another rich source of flavonoids.

Benefits and uses of citrus bioflavonoids

Vitamin C supplementation?

In 1998 a prestigious study (12) showed that "Vitamin C exhibits pro-oxidant properties", and that vitamin C was of little benefit for health and long life and can actually be harmful in some cases. However, this conclusion is misleading. The authors showed that some DNA was both oxidised and also protected from oxidation by vitamin C. What they did not mention was that the protection effect was about ten times stronger! The primary author later capitulated and said "our study shows an overall profound protective effect of this vitamin."

However, it is important to note that artificially high levels of vitamin C can have a variety of harmful effects for some individuals. Those with Crohn's disease, ulcerative colitis, high levels of oxidised LDL, and in particular those with high iron levels, should not supplement high-dose vitamin C.

In contrast, natural levels of vitamin C from food sources are beneficial.

Sugar prevents the absorption of vitamin C. With so much sugar being added to foods today, and with most people having such sweet tastes, it is no wonder that most people have low levels of vitamin C.


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2. Manthey J.A., Grohmann K., Guthrie N. Biological properties of citrus bioflavonoids pertaining to cancer and inflammation. Curr Med Chem. 2001.

3. Chiba H. Hesperidin, a citrus bioflavonoid, inhibits bone loss and decreases serum and hepatic lipids in ovariectomized mice. J Nutr. 2003 Jun.

4. Un Ju Jung, Mi-Kyung Lee, Kyu-Shik Jeong and Myung-Sook Choi. The hypoglycemic effects of hesperidin and naringin are partly mediated by hepatic glucose-regulating enzymes in C57BL/KsJ-db/db mice. J Nutr. 2004.

5. Yamamoto and Gaynor. Therapeutic potential of inhibition of the NF-kB pathway in the treatment of inflammation and cancer. Journal of Clinical Investigation 107 (2): 135.

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8. de Sousa R.R., Queiroz K.C., Souza A.C., Gurgueira S.A., Augusto A.C., Miranda M.A., Peppelenbosch M.P., Ferreira C.V., Aoyama H. Phosphoprotein levels, MAPK activities and NFkappaB expression are affected by fisetin 2007. J Enzyme Inhib Med Chem 22 (4): 439-444.

9. Schuier M., Sies H., Illek B., Fischer H. Cocoa-related flavonoids inhibit CFTR-mediated chloride transport across T84 human colon epithelia. 1 October 2005. J. Nutr. 135 (10): 2320-5. PMID 16177189.

10. Paul Knekt, Jorma Kumpulainen, Ritva Jarvinen, Harri Rissanen, Markku Heliovaara, Antti Reunanen, Timo Hakulinen, and Arpo Aromaa. Flavonoid intake and risk of chronic diseases. September 2002. Am J Clin Nutr 76 (3): 560-8.

11. Spedding G., Ratty A., Middleton E. Inhibition of reverse transcriptases by flavonoids. September 1989. Antiviral Res. 12 (2): 99-110.

12. Podmore ID, Griffiths HR, Herbert KE, Mistry N, Mistry P, Lunec J. Vitamin C exhibits pro-oxidant properties. Nature. 1998 Apr 9;392(6676):559.