Low‐Molecular‐Weight Seaweed‐Derived Polysaccharides Lead to Increased Faecal Bulk but Do Not Alter Human Gut Health Markers

Ciara Bannon, Julia Eckenberger, W Snelling, Chloe Huseyin, Philip J Allsopp, Conall Strain, Priya Ramnani, Roberto Chitarrari, John Grant, Sarah Hotchkiss, Kevin Philp, Ross Campbell, Kieran Tuohy, Marcus Claesson, Nigel G Ternan, JSG Dooley, Roy Sleator, Ian Rowland, Chris IR Gill

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Seaweeds are potentially sustainable crops and are receiving significant interest because of their rich bioactive compound content; including fatty acids, polyphenols, carotenoids, and complex polysaccharides. However, there is little information on the in vivo effects on gut health of the polysaccharides and their low‐molecular‐weight derivatives. Herein, we describe the first investigation into the prebiotic potential of low‐molecular‐weight polysaccharides (LMWPs) derived from alginate and agar in order to validate their in vivo efficacy. We conducted a randomized; placebo‐controlled trial testing the impact of alginate and agar LWMPs on faecal weight and other markers of gut health and on composition of gut microbiota. We show that these LMWPs led to significantly increased faecal bulk (20–30%). Analysis of gut microbiome composition by sequencing indicated
no significant changes attributable to treatment at the phylum and family level, although FISH analysis showed an increase in Faecalibacterium prausnitzii in subjects consuming agar LMWP. Sequence analysis of gut bacteria corroborated with the FISH data, indicating that alginate and agar LWMPs do not alter human gut microbiome health markers. Crucially, our findings suggest an urgent need
for robust and rigorous human in vivo testing—in particular, using refined seaweed extracts.
Original languageEnglish
Article number2988
Pages (from-to)1-16
Number of pages16
Issue number12
Early online date3 Dec 2021
Publication statusPublished online - 3 Dec 2021

Bibliographical note

Funding Information:
Funding: This research was part of the Hydrocolloids as functional food ingredients for gut health project (HYFFI) which was supported by the 7th EU Framework Programme (Grant agreement ID: 222470). The APC received no specific funding for this work.

Publisher Copyright:
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.


  • seaweed
  • faecal bulk
  • bacteriome
  • health benefits


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