Some medical researchers recommend probiotics for kids with acute diarrhea and for the prevention of antibiotic-associated diarrhea (Floch et al 2008).
They note that probiotics may be helpful for certain other ailments, too.
But before you go to the pharmacy or market, it’s important to understand that “probiotics” refers to a large category of microorganisms that coexist in the human body.
Different species of probiotics--even different strains of the same species--may have different effects (Lomax and Calder 2009).
So when you shop for probiotic formulations, it’s a good idea to read the labels. Some commercial preparations contain the wrong bacteria.
In a recent analysis of published studies on probiotics for kids with diarrhea, researcher Brad C. Johnston and colleagues conclude that the most promising microorganisms for therapeutic use are:
• Lactobacillus rhamnosis GG (a strain of bacterium also known as Lactobacillus GG or LGG)
• Lactobacillus sporogenes (another bacterium)
• Saccharomyces boulardii (a yeast)
at doses of 5 to 40 billion colony forming units/day (Johnston et al 2007).
Lactobacillus GG may be especially appropriate as a treatment for childhood diarrhea caused by rotavirus. Unlike other Lactobaccillus species, LGG enhances immunoglobin A responses against rotavirus (Boyle et al 2006). Moreover, there is reason to believe that Lactobaccillus strains are particularly safe (see below).
But not every study of probiotics for kids with diarrhea has shown beneficial effects. Why not?
There are several possibilities.
Research on probiotics is relatively new, and there is still much that we don’t know. Investigators haven’t yet determined which strains of probiotic are best, nor have they worked out the optimal dosage.
Moreover, it appears that manufacturing processes can change the way a probiotic works. In a study comparing different over-the-counter probiotics, researchers found that different sources of the same strain of probiotic had significantly altered properties (Grześkowiak et al 2010).
It’s also possible that the effects of a probiotic depends on the individual--in particular, on what kinds of probiotic microorganisms the individual has already got living in his digestive tract. Different species of probiotics may inhibit each other (Christensen et al 2002).
In addition, it's unlikely that probiotics are good for everyone. For some individuals--like preterm infants and people with compromised immune systems--the use of probiotics could be harmful (see “Safety Concerns” below).
So there are many variables that might account for different outcomes between studies. And it’s also possible that some study outcomes are misleading--the result of chance.
Nonetheless, there is good evidence that probiotics are moderately effective treatments for several ailments (Thomas et al 2010). Here are the highlights of the latest research.
Understanding probiotics for kids
Probiotics are “friendly” microorganisms that colonize the intestines and other parts of the body, including the skin. They are defined by the Food and Agriculture Organization of the United Nations and the World Health Organization as
“Live microorganisms which when administered in adequate amounts confer a health benefit on the host”(FAO/WHO 2001).
These health benefits are currently under study. At minimum, we know that probiotics aid digestion.
There is also evidence that some probiotics help fight infection, either because:
• probiotics compete for space with harmful bacteria (i.e., they keep the growth of harmful bacteria in check) and/or
• probiotics stimulate the immune system in ways that help the body recognize pathogens (Humen et al 2005).
Researchers are testing probiotic therapies for a number of medical conditions. Some examples:
• Probiotics reduce bowel inflammation and appear to be helpful therapy for moderate (but not necessarily severe) cases of diarrhea. For instance, in randomized, double-blind studies Lactobacillus rhamnosus GG has reduced the length and severity of diarrhea infections in babies and young children (Guarino et al 2009; Ruszczyński et al 2008). But the effects of probiotics depends on the strain(s) used, as well as the cause of the diarrhea. L. rhamnosis GG, L. reuteri and B. lactis Bb1 have helped in cases of watery, viral diarrhea and diarrhea caused by antibiotics. They are not as effective for diarrhea caused by a build-up of the normally benign intestinal bacterium Clostridium difficile. For diarrhea caused by C. difficile, a better choice may be the probiotic yeast Saccharomyces boulardii (de Vrese and Marteau 2007).
• Lactobacillus rhamnosus GG may reduce abdominal pain in children suffering from inflammatory bowel disease (Francavilla et al 2010). In a double blind experiment, kids treated with Lactobacillus for 8 weeks experienced less frequent and less severe pain than did kids given placebos.
• Regular consumption of probiotics might reduce the risk of ear and respiratory infections. In one randomized, double-blind study, formula-fed babies were given formula supplemented with Lactobacillus rhamnosus GG and Bifidobacterium lactis Bb-12 from 2 to 12 months of age. Compared to infants given a placebo (plain formula), the treated infants had lower rates of ear infections and fewer recurring respiratory infections (Rautava et al 2009).
• Probiotics--especially lactobacilli and bifidobacteria--might help treat atopic dermatitis, at least for moderately severe (as opposed to mild) cases (Floch et al 2008; Michail et al 2008; Lomax and Calder 2009). Taking probiotics may also prevent atopic dermatitis in babies at high risk for the disease (Betsi et al 2008). However, some studies have failed to show the effect, and have even linked the daily consumption of probiotics by infants with an increase in respiratory allergies(Kopp and Salfeld 2009). For this reason, researchers note there is insufficient evidence to recommend the regular consumption of probiotics by babies for the prevention of atopic disease and other allergies (Kopp and Salfeld 2009; Osborn and Sinn 2007; Thomas et al 2010).
• As of January 2011, there is no convincing evidence that taking probiotics will prevent respiratory allergies. Indeed, as noted above, there is some evidence that the daily consumption of probiotics might put babies at increased risk of developing respiratory allergies. “Up to now no data have been released which report a positive effect of probiotics for the prevention of allergic rhinitis or asthma” (Kopp and Salfeld 2009).
• Regular consumption of probiotics might prevent urinary tract infections, but it’s too early to draw any firm conclusions. Randomized, double-blinded experiments have yet to be done (Williams and Craig 2009).
• The probiotic Lactobacillus reuteri might reduce symptoms of colic in young infants. In a recent study, colicky, breastfed infants given L. reuteri supplements cried less frequently than infants given simethicone drops (Savino et al 2010).
• Probiotics also have metabolic effects and might reduce the risk of obesity (Blackhed et al 2005). But again, this is speculative. More research is needed.
Keep in mind that even the apparent success stories are subject to revision. As several researchers have noted, the science of probiotics is still in its infancy. And it’s worth repeating: the effectiveness of probiotics is likely dependent which strain or species you use, as well as the dose (Lomax and Calder 2009).
Safety concerns about probiotics for kids
Some probiotics occur naturally in most people’s digestive tracts, and, for people with strong immune systems, probiotics have an “excellent safety record” (Boyle et al 2006).
For example, in one randomized, double-blind study of formula-fed infants, researchers put some babies on a formula supplemented with Bifidobacterium lactis. A control group consumed regular formula. Over the course of 7 months, the researchers measured the babies’ growth and immune responses. They found no significant differences between groups (Gibson et al 2009). These results were interpreted as evidence that Bifidobacterium lactis is basically safe for babies.
Another infant formula study tested a combination of Lactobacillus rhamnosus GG and LC705, Bifidobacterium breve Bb99, and Propionibacterium freudenreichii ssp shermanii. Again, researchers found no differences in growth or “serious adverse events” between test infants and infants in a control group (Kukkonen et al 2008).
And the most recent randomized, double-blind study tested the effects of Bifidobacterium lactis Bb12 on formula-fed infants (Holsher et al 2012). Babies supplemented with the probiotic showed evidence of improved immune function, and the supplementation may have been especially beneficial for babies who'd been delivered by C-section.
Still, there are reasons for caution:
• As Touraj Shafai notes, the studies mentioned above don’t demonstrate that breastfed babies should receive probiotics supplements. Although probiotics seem to reduce infection rates in formula-fed babies, breastfeeding seems to have even stronger protective effects (Shafai 2009).
• For some groups, like preterm infants and people who are very ill or suffer from immune deficiency, probiotics may increase the risk of bacterial and fungal infection (Boyle et al 2006).
• Like many “alternative” supplements, over-the-counter probiotics are poorly-regulated. Some brands contain the wrong species or strains. And, as noted above, different manufacturing processes may change the effects of probiotics.
• Because there haven't been many randomized, controlled experiments testing the effects of probiotics for kids, there is still a lot that we don’t understand. As noted above, it's not yet clear which strain(s) are best. Nor do we know what the optimal dosage is.
We should also keep in mind how little we know about the long-term effects of daily probiotics for kids. As researchers representing the American Academy of Pediatrics recently stated, the "long-term impact on the gut microflora in children is unknown" (Thomas et al 2010).
Lactobaccillus in yogurts and other foods
What about probiotics that occur naturally in foods, like fermented dairy products?
It seems likely that Lactobaccillus strains—-especially Lacobacillus rhamnosus GG--are well-tolerated by most people. As Robert J. Boyle and his colleagues have noted, Lactobaccillus strains have been given to healthy infants with no significant adverse outcomes. They’ve even been given to HIV-positive children without ill effects (Boyle et al 2006).
Moreover, there is evidence that babies are supposed to harbor Lactobacilli in their digestive tracts. Human breast milk contains bifidus factor, which promotes the growth of Lactobacillus bifidus in the infant’s digestive tract.
And there has been an informal, population-wide experiment going on in Finland.
Since 1990, Lactobacillus rhamnosus GG has been incorporated into many Finnish foods, and the average Finn has greatly increased his consumption of LGG. Despite this, researchers have detected no increase in blood-born bacterial infections in Finland (Salminen et al 2002).
But are all probiotic foods equally helpful? Probably not. In 2010, Finnish researchers compared the effects of giving people probiotics in capsules, yogurt, and cheese. For two of the probiotics (P. freudenreichii subsp. shermanii JS and Bifidobacteria animalis), yogurt appeared to be the most effective medium (Saxelin et al 2010).
The bottom line?
Probiotics for kids seem beneficial under certain circumstances--particularly for kids with diarrhea. For other conditions, the evidence is less clear. And before buying any probiotic preparations, you should find out what they really contain.
What about prebiotics?
If you're considering daily supplements, another approach is to help the probiotic organisms that already exist in your child's digestive system. Prebiotics are nondigestible food ingredients that help bifidobacteria and lactobaccilli flourish. For more information about boosting probiotics for kids, see this article about prebiotics.
References: Probiotics for kids
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