Prebio: Feeding the Gut Instinct
Evidence suggests nutritional and immunologic effects of stimulating the growth of beneficial bacteria
By keeping good bacteria in the gut at beneficial levels, prebiotics help promote good nutrition and improve a child's immune system.
Prebiotic substances serve as food for bifidobacteria-and to some extent, lactobacilli-two of the many beneficial microorganisms that inhabit the gastrointestinal system. These two microorganisms have been known to exert a positive influence on the gut immune system, thus helping prevent intestinal infections, including diarrhea. They also help promote food absorption through better digestion.
As a means to promote the growth of beneficial bacteria, prebiotics differ from the earlier concept of probiotics.
Probiotics began when people first consumed fermented milk products that contained live microorganisms. The concept rests on the premise that the number of beneficial microorganisms in the gut can be reinforced by ingesting certain live microorganisms. But many experts have also pointed out its shortcoming. The bacteria have to survive the hostile environment of the upper gastrointestinal tract first before they can be effective in the intestines.
This safe passage is very difficult to guarantee. There could be instances in which the stomach may be too acidic to allow the probiotic microorganisms to reach the intestines alive. Whether they have made it there is much more difficult to prove.
Stimulating the Growth
Prebiotics does away with this uncertainty-by stimulating the growth of preexisting good bacteria in our gut instead of importing new ones to augment their population.
Studies have found that when certain nondigestible dietary carbohydrates, such as oligofructose and inulin, are ingested, bifidobacteria-and to some extent, lactobacilli-flourish. The gut flora is able to metabolize and ferment these food ingredients, growing in numbers as they do.
"Prebiotic substances pass through the stomach unaffected; they reach the large colon, where there is a large population of these good bacteria," Dr. Lourdes Genuino, a pediatrician, explains. The beneficial bacteria then proliferate because they prefer prebiotics to other food sources.
Prebiotic substances are also classified as dietary fibers. They reduce the colonic pH, and increase stool weight and bulking. Because of the fermentation, however, gas is produced, which might cause bloating and flatulence.
Dr. Genuino points out that this happens only if the maximum dose is exceeded. Research says that children are able to tolerate two grams per day quite well while adults can take six to eight grams per day with minimal or no adverse effects.
The effect of prebiotic substances on the immune system is also notable. Previous studies abroad have shown that they seem to enhance the immune response to measles vaccination.
"The premise is that the human large gut is the largest immune organ of the body," says Dr. Genuino. She explains that a controlled gut ecosystem could produce greater immune resistance.
In 2002, Dr. Genuino set out to prove locally what foreign studies have consistently demonstrated about prebiotics, with a community-based trial among 69 male infants aged six to eight months in Calauan, Laguna.
She explains that infants at the weaning stage are ideal candidates for prebiotic supplementation. As infants start to take in solid food, the population of their gut flora changes drastically, especially for those just formula-fed.
The infants were randomized and given either a prebiotic milk supplement or standard milk supplement. The study found that the addition of prebiotics resulted in improved bowel function and humoral immune response to measles vaccine in the infants. The results confirm that if the gut instinct for survival in the guts is indulged in favor of microflora with a taste for oligofructose and inulin, the infants' health and immunity profit.
Dr. Genuino recommends, however, that a further study, one that extends up to the first year of the infants, be conducted to see if measles antibody titers remain higher in the prebiotic supplemented group.
For now, evidence suffices to support the benefits of prebiotics in promoting the growth of beneficial bacteria that in turn enhance the gut immune system and promotes better food digestion.
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