Should you take probiotics?

Aaron Deere is a sports nutritionist, functional medicine consultant and advanced personal trainer. He is based in London.

The term probiotics refers to ‘a live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance’[1,2]. The intent of using probiotics is to elicit change which results in reduced amounts of potentially harmful microbes colonising the gut and increasing the populations of beneficial microbes[3].

Strains of lactic acid bacilli, such as Lactobacillus and Bifidobacterium4, are most commonly used in probiotic formulas, with some non-pathogenic strains, such as Escherichia coli (E. coli)5, and Saccharomyces boulardii also regularly used[6,7]. Before identifying the potential benefits of probiotics, it must be recognised there are potential drawbacks to the success of probiotics.

The key areas in which these drawbacks can occur are the following.

Safety Products should have minimal possibilities for transfer of antibiotic resistance and should not adversely affect immune function or disrupt colonocyte function[8,9].
Survivability The products must be resistant to acid and bile secretions during transit, which can potentially reduce chances of largely intact microbes reaching the colon[10].
Volume Must contain sufficient colony forming units (CFUs) to impart beneficial effects. The research suggests a minimum concentration of 106 CFU/mL should be consumed daily for the consumer to be transferred the probiotic effect[11].
Effects on consumer Beneficial microbes should not impart adverse effects on gut transit, nor induce negative side effects, such as excess gas production or bloating.
Product integrity Needs to display a safe record of use, supported by assurances that repeatable, up to date clinical trials have been carried out, with the commercially-available product being the same as involved in the trials and that claims on particular products are not extrapolated onto others[12].

Fundamental findings
Probiotics have been suggested to improve health in multiple ways, ranging from modulation of the immune system via influencing cytokine output and production of antimicrobial agents13, improvement of intestinal barrier function through inhibition of cytokine-induced epithelial cell apoptosis and promotion of epithelial cell growth[14], and the suppression of growth and epithelial binding by pathogenic bacteria[15].

A fundamental finding is that probiotics improve human health by fundamentally stimulating mucosal immune mechanisms and competing with potential pathogens[16]. This mechanism has played a key role in unequivocal evidence for the use of probiotics in treating acute forms of diarrhoea. Daily doses of at least 10 billion CFUs decrease the duration and frequency of acute diarrhoea.

The most evidence to support use is shown for Saccharomyces boulardii,  Lactobacillus rhamnosus GG (LGG) and Lactobacillus acidophilus, with meta-analysis generated evidence showing LGG in particular reduced the duration of acute diarrhoea by 1.2 days[17-19].

Strong evidence also exists that certain probiotic strains enhance immune function. Enhanced phagocytic capacity and the potentiation of humoral immune responses to natural infections was reported at doses of at least 109 CFUs per day, with the strains Lactobacillus johnsonii La1, Bifidobacterium lactis Bb12 and Lactobacillus lactis, suggested to have the greatest immuno-modulating properties[20].

Better lactose digestion
Probiotic bacteria in yogurt and other fermented milk products have been shown to improve lactose digestion in lactose maldigesters, due to microbial galactosidase found within them, and slower overall transit times[21,22]. The evidence suggests that some specific strains, concentrations, and preparations are effective, but further research is required to identify the specific strains and concentrations required to impart a therapeutic effect[23].

Probiotics have also been associated with imparting positive effects on conditions such as cancers, the management of inflammatory bowel disease, protection from gastroenteritis and the lowering of blood cholesterol[24]. Examples include data from small controlled trials suggesting a benefit from VSL#3, a probiotic food supplement, in the primary and secondary prevention of pouchitis[25], and a benefit of probiotics, specifically E. coli[26], showing promise in maintaining remission of ulcerative colitis[27].

While this evidence is encouraging, it is still currently equivocal as to the exact role of probiotics in treating these conditions.

1,8,10 Gibson & Fuller, 2000
2,3,4,9,12 Gibson, 2007
5, 26 Nissle, 1917
6, 27 Kruis et al, 2004
7, 18 Pham et al, 2008
11 Kechagia et al, 2013
13, 15 Jones et al, 2009
14 Yan et al, 2007
16 World Gastroenterology Organisation, 2008
17 Allen et al, 2010
19, 20, 24 Gill et al, 2004
21 de Vrese et al, 2001    
22 Roberfroid, 2000
23 Levri et al, 2005
25 Kuehbacher et al, 2006