The researchers, from the Marine Drug and Food Institute, Ocean University of China, Qingdao, report that the faecal bifidobacteria levels of rats supplemented with AOS (2.5 per cent) increased by 13-fold and 4.7-fold compared with rats fed a control, prebiotic-free diet and a diet supplemented with five per cent fructo-oligosaccharides (FOS).
" In this study, we demonstrated that AOS was a potential novel source of prebiotics both in vitro and in vivo," wrote lead author Ye Wang in the current issue of Nutrition Research.
Prebiotic ingredients, or those that boost the growth of beneficial probiotic bacteria in the gut, are worth about €90 million in the European marketplace but are forecast to reach €179.7 million by 2010, according to Frost & Sullivan.
The market has been largely created by three inulin producers, all based in Europe, but other ingredient manufacturers are increasingly looking to promote the prebiotic effect of their products as evidence suggests that prebiotics could be even more useful than the probiotic bacteria that they feed.
Prebiotics, which are derived from insoluble fibres and oligosaccharides, can be incorporated into a wider variety of end products than probiotic bacteria. They have also benefited from the promotional efforts of probiotic suppliers, who have significantly raised public awareness of gut health in recent years.
"We found that ingestion of 2.5 per cent (wt/vol) AOS increased selectively the numbers of bifidobacteria and lactobacilli of rats, and the increase in bifidobacteria was more significant than that of lactobacilli," said Wang.
"Moreover, the prebiotic effect of AOS was proven to be better than FOS, a prebiotic that has received extensive attention and represents the biggest portion of the current market."
In vitro studies showed that numbers of the friendly gut bacteria bifidobacteria and lactobacilli were significantly increased when the bacteria were cultured in a medium supplemented with AOS, compared to bacterial populations cultured in a control medium.
Compared to FOS, the alginate oligosaccharides are reported to have selectively stimulated the growth of Bifidobacterium bifidum ATCC 29521 and Bifidobacterium longum SMU 27001.
In vivo studies with male Wistar rats are reported to have shown faecal bifidobacteria levels of rats supplemented with AOS (2.5 per cent) increased by 13-fold compared with rats fed a control, prebiotic-free diet. Faecal lactobacilli numbers also increased by five-fold in the AOS-supplemented rats, compared with the controls.
Faecal concentrations of potentially pathogenic bacteria were also said to decrease in rats fed the AOS-supplemented diet, while no such reductions were observed in the control and FOS-fed groups.
"Regardless of the inhibitory effect on potential pathogens, the higher amount of bifidobacteria demonstrated in the cecum of rats resulting from the ingestion of AOS in this study may promote beneficial effects within the gastrointestinal tract," said Wang.
No adverse effects, such as bloating and belching, were documented by the researchers.
"All these findings indicate that AOS has prebiotic properties that can promote health," said the researchers.
"Moreover, it is convenient to prepare AOS from alginate via enzymatic hydrolysis, and its raw material, alginate, is very abundant in the world.
"Further work is needed to investigate its effects in human subjects."
Source: Nutrition Research November 2006, Volume 26, Issue 11, Pages 597-603 "In vivo prebiotic properties of alginate oligosaccharides prepared through enzymatic hydrolysis of alginate" Authors: Y. Wang, F. Han, B. Hu, J. Li and W. Yu