Counting the studies that have been done on probiotics is like counting the organisms in a gram of yoghurt.

Probiotics are live microbial ingestible supplements that can benefit the host (ingesting) organism by favourably altering its intestinal microbial balance.¹ Given the assumption that these microbial supplements must be living, substantial research and development has been dedicated to processes and agents that can prolong their stability and viability throughout the food, beverage and dietary supplements value chain. These include cryo-preservation; prebiotics; microencapsulation; and novel delivery vehicles such as protein-based microparticles, and sausages, along with strain selection.^2,3,4,5

But do the organisms need to be alive to be effective?

A number of basic and clinical research studies have been conducted with a heat-killed, freeze-dried, human gut-derived strain (LB) of Lactobacillus acidophilus (Lacteol Fort, Homdan, France, first isolated in 1907) with a fermented culture medium. Earlier studies conducted among paediatric and adult populations showed efficacy in acute diarrhoeal episodes.^6,7 A double-blind, placebo-controlled crossover trial in a population of 18 inflammatory bowel disease patients revealed significant clinical efficacy with a daily dose of 10 billion organisms taken twice daily.⁸ Although a research-validated symptom score was not used, the crossover design (with a two-week washout) augments the rigor of the trial.

A more recent study among 73 paediatric patients (ages 3-24 months) with acute watery diarrhoea and mild to moderate dehydration revealed that a dose of 10 billion LB cells, taken as Lacteol Fort (twice daily), produced significant reductions in the duration of diarrhoea, especially among infants who had not received prior antibiotic therapy.⁹ The LB strain/culture medium that comprises Lacteol Fort exhibits gut cell adhesive and pathogen excluding properties, which appear to be thermostable.^10,11

Collectively, these data demonstrate a 'probiotic' effect with dead organisms. The ideal assessment would be a head-to-head comparator study assessing a heat-killed strain against a live probiotic strain.

One study did just that. It was a multi-centre, randomised, open-label four-week study that assigned 137 adults with chronic diarrhoea to receive Lacteol Fort (10 billion organisms twice daily) or a live Lactobacillus acidophilus chewable tablet that contained 400mg of skimmed fermented milk per tablet (five tablets thrice daily; strain not specified and viability not validated; Lacidophilin brand, Tai Ge Pharma, China).^12,13 The Lacteol group showed significantly superior efficacy in symptom scores and overall efficacy.

The obvious major weaknesses of this study include the complete lack of characterisation of the 'live' probiotic strain, the absence of a placebo control, and the lack of blinding. A definitive and rigorous head-to-head comparator study is warranted, including assessment of the efficacy of the Lacteol Fort fermented culture medium alone.

References
1. Fuller R. Probiotics in man and animals. J Appl Bacteriol 1989;66:365—78.
2. Capela P, et al. Effect of cryoprotectants, prebiotics and microencapsulation on survival of probiotic organisms in yoghurt and freeze-dried yoghurt. Food Res Intl 2006;39:203—11.
3. Chen L, et al. Food protein-based materials as nutraceutical delivery systems. Trends Food Sci Technol 2005;doi:10.1016/j.tifs.2005.12.011.
4. Klingberg TD, et al. The survival and persistence in the human gastrointestinal tract of five potential probiotic lactobacilli consumed as freeze-dried cultures or as probiotic sausage. Intl J Food Microbiol 2006;doi:10.1016/j.ijfoodmicro.2006.01.014.
5. Lavermicocca P, et al. Study of adhesion and survival of lactobacilli and bifidobacteria on table olives with the aim of formulating a new probiotic food. Appl Environ Microbiol 2005;71:4233-40.
6. Boulloche J, et al. Management of acute diarrhoea in infants and young children: controlled study of the antidiarrhoeal efficacy of killed L. acidophilus (LB strain) versus a placebo and a reference drug (loperamide). Ann Pediatr 1994;41:457-63.
7. Bodilis JY. Controlled clinical trial of Lacteol Fort compared with a placebo and reference drug in the treatment of acute diarrhea in the adult. Med Actuelle 1983;10:232-5.
8. Halpern GH, et al. Treatment of irritable bowel syndrome with Lacteol Fort: a randomized, double-blind, cross-over trial. Am J Gastroenterol 1996;91:1579-85.
9. Simakachorn N, et al. Clinical evaluation of the addition of lyophilized, heat-killed Lactobacillus acidophilus LB to oral rehydration therapy in the treatment of acute diarrhea in children. J Ped Gastroenterol Nutr 2000;30:68-72.
10. Chauvi?re G, et al. Adhesion of human Lactobacillus acidophilus strain LB to human enterocyte-like Caco-2 cells. J Gen Microbiol 1992;138:1689-96.
11. Coconnier MH, et al. Antibacterial effect of the adhering human Lactobacillus acidophilus strain LB. Antimicrob Agents Chemother 1997;41:1046-52.
12. Xiao SD, et al. Multicenter randomized controlled trial of heat-killed Lactobacillus acidophilus LB in patients with chronic diarrhea Chin J Dig Dis 2002;3:167-71.
13. Xiao SD, et al. Multicenter, randomized, controlled trial of heat-killed Lactobacillus acidophilus LB in patients with chronic diarrhea Adv Ther 2003;20:253-60.

Anthony Almada, MSc, is president and chief scientific officer of IMAGINutrition.
Respond: [email protected]