In 1907, Nobel Laureate Eli Metchnikoff put forth the theory that intestinal colons contain putrefactive bacteria and that by consuming fermented milk, lives would be longer and more disease-free.
Today, good scientific evidence exists to support the ability of probiotics (whether living) to increase a body's resistance to enteric pathogens, speed recovery from antibiotic-associated diarrhea, reduce hypertension, and assist with lactose digestion. Great scientific evidence supports their ability to stimulate the immune system and improve urinary and vaginal tract health.2 The gastrointestinal tract is, in fact, the most powerful immunological organ in our bodies.
Backed by extensive investigation, most of the scientific community accepts probiotic benefits. However, there is not yet unequivocal proof that these roles occur. Science must go to the next level in which research is subjected to the rigors of pharmaceutical cause-and-effect relationships of double-blind placebo studies with validated markers and validated outcomes.
To validate
the probiotic concept, the molecular mechanisms and active
components responsible for these organisms' benefits must
be defined.3 Clinical studies should be performed
that relate specific bacterial characteristics with the physiological
or health-based outcome. This means making comparisons between
a probiotic culture, with a particular property (e.g., adhesion),
and its variant, deficient in that property (e.g., no adhesion),
to determine its functionality in the GI tract (e.g., colonization potential).
Genetic Solutions
The continual development and commercial introduction of new probiotic strains present new challenges to the scientific community. Thus, the question arises as to "who's who" in these new cultures and what is their molecular taxonomy. For example, what we use to think of asLactobacillus acidophilusis now known to be a mix of six different species. One is still consideredLactobacillus acidophilusbut others includeL. johnsonii andL. gasseri, which are commonly found in humans and are considered to evoke "acidophilus-like" probiotic properties.In one study, we examined 20 consumer products claiming to contain L. acidophilus and sequenced their 16S DNA gene to make a true identification. Only eight contained the organism they claimed. Others included organisms such as L. gallinarum or delbrueckii or Pediococcus pentosaceus. Bottom line, no product should be on the market today that doesn't have what it claims.
On a positive note, when the eight acidophilus cultures were fingerprinted, all had very similar genetic content. This means that as good scientific information is developed, it should positively impact everyone selling products with L. acidophilus.
Advances in genetic research allow us to study intestinal flora in vivo (in the body) like never before. The DNA from microorganisms in fecal material can be isolated, amplified, and fingerprinted. Using these fingerprints, we can identify the bacteria present and monitor the changes in this microflora after changing a diet or adding a probiotic culture.
The future of
probiotics may include the novel uses of these organisms.
For example, we know that some probiotic cultures can adhere
to mucosal intestinal cells and that close interaction promotes
stimulation of the immune system. As this relationship is
better understood, it is likely that probiotic strains will
be developed to move beyond their current role as immune-enhancers
to be delivery vehicles for bioactive compounds, such as vaccines,
enzymes, antimicrobials, and bioactive peptides. NS
References
1 Guarner, F. and G.J. Schaafsma. 1998. Probiotics.Int. J. Food Microbiol. 39: 237-238.2 Klaenhammer, T.R. 2000, Probiotic Bacteria: Today and Tomorrow.J. Nutrition. 130: 415S-416S.
3 Klaenhammer,
T.R. and M.J Kullen. 1999. Selection and design of probiotics.
Int'l. J. Food Microbiology. 50: 45-57.
