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Citrus Flavonoids | Polyphenols

Citrus flavonoids have the dual capacity to leverage the microbiome and host-immune health potential.

MicrobiomeX, a citrus fruit extract, has been specifically designed to positively modulate the gut microbiome by increasing butyrate producing Firmicutes (especially Clostridium Cluster XIVa) in the mucus membrane, and subsequently increasing butyrate and propionate levels throughout the colon.

A randomised, double-blind, placebo-controlled, parallel group study in 50 participants over 12 weeks (n=23 MicrobiomeX; n=27 placebo) showed a significant increase in butyrate and positive change to the butyrate/acetate ratio (p<0.05) compared to baseline with daily administration of 500mg (1).

Furthermore, in the MicrobiomeX group, there was a strong trend towards a reduction in faecal calprotectin and pathogen load.

Prebiotics have been shown to enhance mucus production (2, 3). It has been postulated that an increase in mucus stimulates the release of mucosal butyrate producers towards the gut lumen, and thus increases butyrate levels (4). Furthermore, this may enhance the bioavailability of butyrate as it’s released close to the epithelium, which could be particularly useful for IBD patients where transport of butyrate to colonocytes is impaired.


Citrus flavonoids & cognition

A recent review examined 21 studies with emphasis on the subclass and dose of flavonoids administered, the cognitive domains affected by flavonoid supplementation, and the effect size of the response. The concluding statement was that evidence suggests flavonoids to be beneficial to attention, working memory, and psychomotor processing speed in a general population (5).

Supplementation with flavone-rich orange juice was shown to significantly improve the digit symbol substitution task, a measure of psychomotor processing speed compared to both the sugar-matched control and baseline, in a crossover intervention study (6). Additionally, an increase in cerebral blood flow was observed by fMRI. The flavonoid content in this study was low, thus if flavonoids work in a dose-dependent manner, a higher dose may have elicited increased cognitive benefit.

Indeed, a randomised, double-blind, crossover study using a greater total orange flavonoid content, improved psychomotor performance at 2 (p<0.01) and 6 (p<0.05) hours compared to placebo and baseline in middle-aged male subjects. Additionally, the orange juice attenuated a decline in subjective alertness throughout the testing period, compared to a sugar-matched control (p<0.05) (7).


  1. Microbiome X white paper,
  2. Ten Bruggencate, M., Bovee-Oudenhoven, J., Lettink-Wissink, G., et al. (2004). Dietary fructo-oligosaccharides and inulin decrease resistance of rats to salmonella: protective role of calcium. Gut 53: 530–535.
  3. Abbeele P., Gerard P., Rabot S., et al. (2011). Arabinoxylans and inulin differentially modulate the mucosal and luminal gut microbiota and mucin-degradation in humanized rats. Environ Microbiol 13: 2667–2680.
  4. Abeelle, P., Belzer, C., Goossens, M., et al. (2013). Butyrate-producing Clostridium cluster XIVa species specifically colonize mucins in an in vitro gut model. The ISME Journal 7, 949–961
  5. Bell L, Lamport D, Butler L, Williams C (2015) A Review of the Cognitive Effects Observed in Humans Following Acute Supplementation with Flavonoids, and Their Associated Mechanisms of Action Nutrients. 7, 10290–10306
  6. Lamport, D.J., Pal, D., Macready, A.L., et al. (2016). The effects of flavanone-rich citrus juice on cognitive function and cerebral blood flow: An acute, randomised, placebo-controlled crossover trial in healthy young adults. British J. Nutr. 116(12):2160-2168
  7. Alharbi, M.H., Lamport, D.J., Dodd, G.F., et al. (2016). Flavonoid rich orange juice is associated with acute improvements in cognitive function in healthy middle-aged males. Eur. J. Nutr. 55:2021–2029

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