Microbiome Health Focus: What Constitutes a Prebiotic?

Prebiotics have generally been viewed as energy sources for the various microrganisms that inhabit the human gut microbiome, with this energy derived from select dietary fibre sources. However, recently there has been a re-evaluation of what constitutes a prebiotic.


The latest definition of a prebiotic was developed by a range of specialists under the auspices of the International Scientific Association for Probiotics and Prebiotics (ISAPP) in 2016. This updated definition is:  “a substrate that is selectively utilized by host microorganisms conferring a health benefit”. This widens the scope of the compounds that can now be considered to exhibit prebiotic activity. Fundamental to this new definition is that the material must “confer a beneficial physiological effect on the host by the selective utilization of a compound by gut bacteria”

In the light of this new definition, Marigot, from recent published research on Aquamin and working as a key member of the Global Prebiotic Association (GPA) have concluded that Aquamin can be considered a prebiotic. An examination of this research helps to understand why. 

The Science to date

A growing amount of scientific evidence suggests that colon microbiota of Irritable Bowel Syndrome (IBS) patients differ from that of healthy subjects. Alterations in several different microbial species, genera or groups have been reported but it is noteworthy that the results of different studies have to some extent been contradictory. An on-going in-vitro study assessing the impact of Aquamin on an IBS-derived, gut microbial population has led to some interesting  results. In this study, the levels of gas production and individual short chain fatty acids (SCFAs) were measured in the absence of or with increasing doses of Aquamin seaweed complex. The three most abundant SCFAs are acetic, propionic, and butyric acids. In the colon simulation model used in the study, the total acid concentration was used to assess the overall fermentation activity while the relative abundance of individual acids indicated the respective activity of different fermentation pathways. Despite no observed change in overall gas production, a dose-dependent increase in total SCFA production was recorded, ranging from 9% to 17% when compared to the control. Acetate, associated with weight control and a healthy immune system, production was stimulated by between 7-9% and propionic acid by 17-44%. Interestingly, there were no significant changes in butyric acid levels at any time point or with any concentration of the dietary supplement. 

Lactic acid is the strongest of the common SCFAs produced by GI bacteria and its accumulation is considered a negative event for the lower intestinal tract. Inclusion of Aquamin seaweed complex resulted in decreased levels of lactic acid as well as a dose-dependent buffering action on colonic pH in comparison to the control treatment. These results indicate a substantial alteration in bacterial fermentation patterns and a more beneficial phenotype for relieving IBS symptoms currently being investigated in dietary intervention studies. (Felice et al., 2020)

The above results were reinforced in two more recent studies, one in animals and the other in humans. (Crowley et al., 2018) demonstrated that the gut microbial diversity and species enrichment were significantly enhanced in adult rats when they were fed a blend of Aquamin seaweed complex and Aquamin marine magnesium for six weeks. Furthermore, in our first FDA-approved human study, thirty healthy adult participants (10/group) were enrolled in a 90-day trial in which Aquamin seaweed complex (800mg Ca/day) was compared to calcium alone or placebo. Colon biopsies and stool specimens were obtained and analysed before and after the intervention and the changes to the gut microbiota were recorded and significant changes in microbiota were observed  (Aslam et al., 2019). This study also recorded a reduction in total bile acids and an increase in the level of the SCFAs, (Fig 9).  SCFAs are produced when ‘good’ bacteria ferment indigestible foods. They are the main energy source of cells lining the colon making them crucial to gastrointestinal health. Taken together these results are considered highly beneficial for the gut. No significant changes in bile acids or SCFAs were seen with calcium alone or placebo.


Vitafoods 2018