The human body hosts a surprisingly large number of microorganisms, both on the skin and in the gut. The majority of these microorganisms, collectively called our microflora, are harmless as long as they stay where they belong. The microorganisms in the digestive tract feed on indigestible components of the food we eat, and some are even helpful and beneficial to health.
> Probiotics <
Most of the helpful microorganisms are bacteria of the Lactobacillus or Bifidobacterium groups, along with a few yeasts, like Saccharomyces cereviciae (sometimes incorrectly called Saccharomyces boulardii). The term probiotics describes both foods containing live, active cultures of these beneficial microorganisms as well as the cultures themselves. In order for a food to be truly probiotic, the number of beneficial microorganisms must be high enough to have a beneficial effect on the body.
Probiotics have been used for centuries, in the form of fermented foods and cultured milk products, including yogurts and kefir. Today many foods claim to be fortified with probiotics, prebiotics or both. Unfortunately, the United States Food and Drug Administration has not developed standards to define these terms. The mere presence of good bacteria in a product is not sufficient to make it probiotic. Remember, the concentration of bacteria must be high enough to confer beneficial effects. Unfortunately, the available information does not clearly demonstrate how many bacteria are necessary, but it is likely in the billions.
> Prebiotics <
Prebiotics, on the other hand, are carbohydrates that the human body cannot digest, but which promote the growth of the beneficial bacteria present in the colon. Using probiotics and prebiotics together can boost their beneficial effects. When both probiotics and prebiotics are present in a single food or supplement, it is called a synbiotic.
The best-known prebiotic is inulin, a soluble fiber made from chains of fructose molecules. It exists in many plants, including bananas, garlic, onlion, artichoke and asparagus, creating yet another reason to eat your vegetables. Some prebiotics may help increase the absorption of certain nutrients, like calcium, but it appears this effect is limited to certain forms of inulin.
> The Benefits and The Hype <
Probiotics, prebiotics and synbiotics are not cure-alls, and the jury is still out on exactly what they can do. A study in 2005 suggests that use of synbiotics may reduce the inflammation associated with ulcerative colitis. Studies published in 2005 and 2008 in Alimentary Pharmacology & Therapeutics suggest that probiotics may provide some symptom relief for people with Irritable Bowel Syndrome.
Even if these results are verified, merely eating a yogurt and a banana will not necessarily provide the benefits you seek. Remember, again, that in order to be probiotic, foods must contain live and active cultures of specific bacteria or yeast in sufficient quantity to promote beneficial effects on the body (not on the manufactures bottom line).
In recent years, more and more foods have been promoted as being probiotic or symbiotic, including foods that don't normally contain either. The concern about these fortified foods is that some manufacturers are adding just a few bacteria and calling it live and active (which may be true, but that does not make it probiotic). In addition, adding live and active bacteria at the beginning of manufacture does not make a food probiotic if those bacteria are dead in the final product.
Concern also exists with regard to consuming an excess of prebiotics, especially inulin. The thinking is that if the probiotic organisms are unable to use it all, then it might also feed harmful bacteria, causing illness. Although there is no evidence of this, we do not currently know enough about the microbial balance to understand fully the effects of supplementation of these foods.
Evidence does support the beneficial effects of probiotics and prebiotics, but this evidence is based largely on consumption of naturally occurring forms. The evidence for the efficacy of different laboratory strains of the same bacteria is mixed, so there are no guarantees about the particular strain in a particular food. For now, your healthiest option is to eat a wide variety of healthful foods, many of which naturally contain probiotics and prebiotics.