The gut is
home to trillions of microbes collectively known as the gut microbiota. The
growth of these microbes ultimately depends upon food entering via the host’s
diet. Microbes directly metabolise food components and mucus lining the GI tract 1, generated metabolites are further
available to other microbes and the host 2. In this way trophic chains
underlie the symbiosis between microbes and the host. Not surprisingly then many
food components have been shown to alter the balance and metabolic activities
of the gut microbiota. Basic macronutrients (i.e. protein, carbohydrates and
fats) can alter the balance and activity of specific bacterial communities 3–5. Poorly digestible food
components such as fibre pass through the entire intestines directly feeding
bacteria. Soluble fibres in particular (e.g. FOS/inulin, GOS, MOS, etc.) are
well known for their prebiotic effects (i.e. their ability to preferentially promote
the growth of beneficial bacteria).
However less
well recognised is the ability of other poorly absorbed plant phytochemicals such
as polyphenols to modulate the gut microbiota. Polyphenols are a group of
chemicals containing multiple phenol (C6H5OH) structural
units. Phenolic compounds are abundant in many plant food stuffs highly revered
for their health-promoting effects such as berries, green tea, cocoa and nuts 6. Common phenolic compounds
include flavanols, flavonoids and anthrocyanins (for a full list see Wiki). Most polyphenols are poorly
digested and have low bioavailability in humans although some can be partially
absorbed 6. As such substantial
quantities of polyphenols pass into the colon and are metabolised by the gut
microbiota which can generate smaller absorbable molecules 6–8. Several studies have begun
to show that phenolic compounds exert prebiotic effects. Consumption of high-flavanol
cocoa versus low-flavanol cocoa was reported to increase Lactobacilli and Bifidobacteria
while decreasing Clostridia levels
in humans 9. These microbial changes were
paralleled by significant reductions in plasma triacylglycerol and C-reactive
protein (CRP) concentrations 9. Blueberries (rich in
anthocyanins) have been shown to possess prebiotic effects in vitro and in rats
10,11. In humans consumption of a
wild blueberry powder drink was shown to boost Bifidobacteria levels 12. Consumption of red wine
polyphenols increased the levels of several bacterial genera including Bifidobacteria which correlated changes
to blood markers in humans 13. Selenium-rich green tea
increased Lactobacilli and Bifidobacteria while decreasing Clostridia and Bacteroides levels in rats 14. Green tea consumption has
also been reported to increase Bifidobacteria
levels in humans 15. In an animal model of
obesity administration of a polyphenol-rich extract of pomegranate peel
increased Bifidobacteria levels and
alleviated tissue inflammation and hypercholesterolaemia 16. In addition to the prebiotic
effects reviewed above plant phenolic compounds have also been reported to preferentially
inhibit important pathogens (e.g. Salmonella, C. perfringens, C.
difficile and H. pylori) 17–23.
Prebiotics have never (knowingly)
been trialled in ME/CFS however it is notable that in a small study consumption
of a high-cocoa/polyphenol-rich chocolate improved fatigue and mood symptoms in
CFS patients 24. Beneficial effects were
attributed to the polyphenol content in this chocolate although it is not clear
what the levels of other important nutrients were (e.g. magnesium). Polyphenols
in cocoa do have some bioavailability and so could mediate some direct effects
such as antioxidant activity 6. However much of the
polyphenol content in cocoa may pass into the colon 9. As described above cocoa
exhibits robust prebiotic activity in humans which correlates with systemic
blood markers 9. Indeed pre and probiotics favourably
modulate many facets of host immune, metabolic and neurological function. The
prebiotic effects of cocoa have been found to correlate with blood CRP levels 9; CRP is a marker of
inflammation and is often slightly increased in ME/CFS 25–28. Hence it seems logical to
suppose the beneficial effects of cocoa reported in CFS patients may involve
modulation of the gut microbiota.
References
1. Kim, Y. S.
& Ho, S. B. Intestinal goblet cells and mucins in health and disease:
recent insights and progress. Curr. Gastroenterol. Rep. 12,
319–30 (2010).
2. Bourriaud, C. et al. Lactate is
mainly fermented to butyrate by human intestinal microfloras but
inter-individual variation is evident. J. Appl. Microbiol. 99,
201–12 (2005).
3. Brown, K., DeCoffe, D., Molcan, E.
& Gibson, D. L. Diet-induced dysbiosis of the intestinal microbiota and the
effects on immunity and disease. Nutrients 4, 1095–119 (2012).
4. Carbonero, F., Benefiel, A. C.,
Alizadeh-Ghamsari, A. H. & Gaskins, H. R. Microbial pathways in colonic
sulfur metabolism and links with health and disease. Front. Physiol. 3,
448 (2012).
5. Ghosh, S. et al. Fish oil
attenuates omega-6 polyunsaturated fatty acid-induced dysbiosis and infectious
colitis but impairs LPS dephosphorylation activity causing sepsis. PLoS One
8, e55468 (2013).
6. Del Rio, D. et al. Dietary
(poly)phenolics in human health: structures, bioavailability, and evidence of
protective effects against chronic diseases. Antioxid. Redox Signal. 18,
1818–92 (2013).
7. Bolca, S., Van de Wiele, T. &
Possemiers, S. Gut metabotypes govern health effects of dietary polyphenols. Curr.
Opin. Biotechnol. 24, 220–5 (2013).
8. Van Duynhoven, J. et al.
Metabolic fate of polyphenols in the human superorganism. Proc. Natl. Acad.
Sci. U. S. A. 108 Suppl , 4531–8 (2011).
9. Tzounis, X. et al. Prebiotic
evaluation of cocoa-derived flavanols in healthy humans by using a randomized,
controlled, double-blind, crossover intervention study. Am. J. Clin. Nutr.
93, 62–72 (2011).
10. Molan, A., Lila, M. & Ravindran, G.
Blueberries: Genotype-dependent variation in antioxidant, free-radical
scavenging, and prebiotic activities. 427–434 (2010). at
11. Molan, A. L., Lila, M. A., Mawson, J.
& De, S. In vitro and in vivo evaluation of the prebiotic activity of
water-soluble blueberry extracts. World J. Microbiol. Biotechnol. 25,
1243–1249 (2009).
12. Vendrame, S. et al. Six-week
consumption of a wild blueberry powder drink increases bifidobacteria in the
human gut. J. Agric. Food Chem. 59, 12815–20 (2011).
13. Queipo-Ortuño, M. I. et al.
Influence of red wine polyphenols and ethanol on the gut microbiota ecology and
biochemical biomarkers. Am. J. Clin. Nutr. 95, 1323–34 (2012).
14. Molan, A.-L., Liu, Z. & Tiwari, R.
The ability of green tea to positively modulate key markers of gastrointestinal
function in rats. Phytother. Res. 24, 1614–9 (2010).
15. Jin, J.-S., Touyama, M., Hisada, T. &
Benno, Y. Effects of green tea consumption on human fecal microbiota with
special reference to Bifidobacterium species. Microbiol. Immunol. 56,
729–39 (2012).
16. Neyrinck, A. M. et al.
Polyphenol-rich extract of pomegranate peel alleviates tissue inflammation and
hypercholesterolaemia in high-fat diet-induced obese mice: potential
implication of the gut microbiota. Br. J. Nutr. 109, 802–9
(2013).
17. Puupponen-Pimiä, R. et al.
Antimicrobial properties of phenolic compounds from berries. J. Appl.
Microbiol. 90, 494–507 (2001).
18. Puupponen-Pimiä, R. et al. Berry
phenolics selectively inhibit the growth of intestinal pathogens. J. Appl.
Microbiol. 98, 991–1000 (2005).
19. Chatterjee, A., Yasmin, T., Bagchi, D.
& Stohs, S. J. Inhibition of Helicobacter pylori in vitro by various berry
extracts, with enhanced susceptibility to clarithromycin. Mol. Cell. Biochem.
265, 19–26 (2004).
20. Ankolekar, C. et al. Inhibitory
potential of tea polyphenolics and influence of extraction time against
Helicobacter pylori and lack of inhibition of beneficial lactic acid bacteria. J.
Med. Food 14, 1321–9 (2011).
21. Juneja, V. K., Bari, M. L., Inatsu, Y.,
Kawamoto, S. & Friedman, M. Control of Clostridium perfringens spores by
green tea leaf extracts during cooling of cooked ground beef, chicken, and
pork. J. Food Prot. 70, 1429–33 (2007).
22. Taguri, T., Tanaka, T. & Kouno, I.
Antimicrobial activity of 10 different plant polyphenols against bacteria
causing food-borne disease. Biol. Pharm. Bull. 27, 1965–9 (2004).
23. Lee, H. C., Jenner, A. M., Low, C. S.
& Lee, Y. K. Effect of tea phenolics and their aromatic fecal bacterial
metabolites on intestinal microbiota. Res. Microbiol. 157, 876–84
(2006).
24. Sathyapalan, T., Beckett, S., Rigby, A.
S., Mellor, D. D. & Atkin, S. L. High cocoa polyphenol rich chocolate may
reduce the burden of the symptoms in chronic fatigue syndrome. Nutr. J. 9,
55 (2010).
25. Groeger, D. et al. Bifidobacterium
infantis 35624 modulates host inflammatory processes beyond the gut. Gut
Microbes 4, (2013).
26. Spence, V. A., Kennedy, G., Belch, J. J.
F., Hill, A. & Khan, F. Low-grade inflammation and arterial wave reflection
in patients with chronic fatigue syndrome. Clin. Sci. (Lond). 114,
561–6 (2008).
27. Newton, D. J. et al. Large and
small artery endothelial dysfunction in chronic fatigue syndrome. Int. J.
Cardiol. 154, 335–6 (2012).
28. Hokama, Y. et al. Acute phase
phospholipids related to the cardiolipin of mitochondria in the sera of
patients with chronic fatigue syndrome (CFS), chronic Ciguatera fish poisoning
(CCFP), and other diseases attributed to chemicals, Gulf War, and marine
toxins. J. Clin. Lab. Anal. 22, 99–105 (2008).
No comments:
Post a Comment