Prebiotic effects of konjac get control trial boost

By Stephen Daniells

- Last updated on GMT

Related tags: Gut flora, Dietary fiber, Lactobacillus

A daily supplement of konjac glucomannan to a low-fibre diet
boosted lactic acid bacteria and colonic fermentation, and promoted
defecation frequency, says a new study from Taiwan.

The science supporting the prebiotic effects of konjac glucomannan (KGM), most commonly known for its use as a texturant in food products, is limited, but the results of the new placebo-controlled study, published in the current issue of the journal Nutrition​ (Vol. 22, pp. 1112-1119), could help an ingredient considerably less well-known and researched than inulin and fructo-oligosaccharide.

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 benefitted from the promotional efforts of probiotic suppliers, who have significantly raised public awareness of gut health in recent years.

Early findings by French company, Kalys, said to be the only European supplier of konjac or glucomannan flour, reported that when broken up into smaller molecules, through a process called 'cracking', glucomannan oligosaccharides may rival and perhaps better the prebiotic effect on lactobacillus and bifidobacteria in vitro​ than inulin and fructooligosaccharide.

The new study, by researchers from Chung Shan Medical University and National Cheng Kung University in Taiwan, looked at the effects of either a KGM supplement (4.5 grams per day, Fukar International Company) or a placebo (corn starch) on the gastrointestinal response of eight adults (average age 35) with a low dietary fibre intake (less than 20 g/d).

After 21-days of supplementation, lead researcher Hsiao-Ling Chen and co-workers report that populations of the so-called beneficial bacteria Bifidobacterium​ spp. and Lactobacillus​ spp. both significantly increased as a function of total bacteria (7.1 and 2.1, respectively), while levels of the potentially harmful bacteria, Clostridium​ spp., decreased (5.2 per cent), relative to the placebo group.

The mean defecation frequency was also found to increase by about 27 per cent per day, and the stoll weight (both wet and dry) also increased, said the researchers (30 and 22 per cent, respectively.

Short-chain fatty acid concentrations also increased in the faeces after supplementation with KGM, compared to placebo.

"This study demonstrated three beneficial aspects for supplementation of KGM into a low-fiber diet in healthy adults,"​ said the researchers.

"First, the dose of KGM powder (1.5 g/meal, 4.5 g/d) was compliant for healthy adults. There were no gastrointestinal side effects, such as extra-abdominal cramping, borborygmi, bloating, and flatulence, with the KGM supplement. Second, the KGM supplement exerted laxative and bulky effects. Third, KGM improved the colonic ecology by decreasing fecal pH and increasing the relative proportions of bifidobacteria and lactobacilli in feces."

"Supplementation of KGM into a low-fibre diet promoted the defecation frequency in healthy adults, possibly by increasing the stool bulk, thus promoting the growth of lactic acid bacteria and colonic fermentation,"​ concluded the researchers.

Significant additional study in larger sample populations to further clarify the prebiotic effects of the glucomannan powder are needed, and the science supporting potential benefits continues to lag way behind that of inulin and oligosaccharides that have an extensive body of research reporting benefits for intestinal health, bone health, and potential protection against colon cancer and boosting immune function.

The study was funded by a grant from the Taiwanese National Science Council.

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