Nowadays, the terms prebiotics and symbiotics are popping up in the scientific literature. Most of us are already familiar with the term, probiotics. How could we not be? They’re added to multiple foods and drinks. Yet, probiotics aren’t the whole story. Just like us, beneficial bacteria need food to flourish and their food is prebiotics. Luckily, many can be found in regular food. Yet, many prebiotic supplements are also sold. Is prebiotic-enriched food enough to support good bacteria, or do we need supplementation too?
Prebiotics are a relatively new concept that was introduced in 1995. The scientific definition of prebiotics is ‘‘selectively fermented ingredients that allow specific changes, both in the composition and/or activity in the gastrointestinal microflora that confer benefits upon host wellbeing and health.’’ In layman’s terms, this means that prebiotics act as a kind of food that supports the growth of probiotics in the intestinal tract.
This food is in the form of indigestible sugars, what we would call fiber. But, they’re not just any fiber. Prebiotics must be able to enter the large intestine and be digested by the intestinal microflora. Many vegetable fibers have a prebiotic effect. However, some interesting prebiotics have also been discovered in human milk. In general, the most widely-studied prebiotics are inulin, fructo-oligosaccharide (FOS) and galacto-oligosaccharides (GOS).
There are multitudes of different prebiotics that can be obtained from food. Agave, banana, chicory, dandelion, garlic, artichokes, onion, yams and leeks all contain high amounts of inulin. The majority of these, as well as many cereal grains, also contain fructo-oligosaccharide (FOS). Studies with these two prebiotics show that they are extremely capable of increasing the relative populations of bifidobacteria in the colon. Interestingly, soybeans are also shown to have unique oligosaccharides that stimulate bifodobacteria as well.
One problem, however, is that large amounts of prebiotic foods need to be digested to provide the same amounts used in studies seeing prebiotic benefits. The average Western diet, for example, is estimated to provide only several grams of inulin per day. Most studies performed with inulin or FOS gave their subjects generally more than 6 grams per day of the prebiotic supplement.
This is not to say that’s it’s impossible to get enough prebiotics from food. Those eating raw foods should get copious amounts of food-based inulin and FOS into their diet. Unfortunately, cooking does seriously diminish the amounts of prebiotics in food. A raw onion contains approximately twice as much prebiotic fiber as a cooked one. To get 6 grams of inulin, one would have to eat 1.8 oz of raw onion as compared to ¼ pound of cooked ones. Prehistoric, hunter-gather populations are estimated to have consumed 135 grams of inulin per day. While emulating that amount would be hard; a diet rich in fruits in vegetables, especially raw ones, should be sufficient to get the minimum 6 grams.
While focusing on eating more veggies and grains is a great way to get prebiotics in one’s diet, it may not be the most practical or even optimal solution for some. Simply said, there are many who would balk at eating large amounts of vegetables per day, and those who would benefit from more than the minimal amounts of prebiotics.
People who might need additional supplementation beyond prebiotic foods are those with health issues. Studies have shown that individuals with inflammatory bowel disease, antibiotic-associated diarrhea, traveller’s diarrhea and low calcium absorption can benefit from prebiotic supplementation. In these cases, the amounts of prebiotic given in these studies fluctuated between 10-30 grams per day.
Furthermore, there are prebiotics that just can’t be found in vegetables. Many prebiotics like GOS and lactulose are actually manufactured and are based on indigestible sugars found in milk. The potential of using milk prebiotics is that they may be more powerful than the vegetable-based ones. However, more comparative studies need to be done.
Food vs. Supplements
The choice whether to enrich your diet with prebiotic foods or take a prebiotic supplement or even a combination of the two can be confusing. Each is a valid option. A good first step is to determine why you want to improve your intestinal flora in the first place. Once that question is answered, the scientific literature can be examined for additional information. It might also be wise to consult a nutritionist. Whilst most prebiotic foods and supplements are considered safe, ingesting too much too soon can cause bloating and gas even in healthy individuals.
Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment.
- Mark’s Daily Apple – A Primal Primer: Prebiotics, (http://www.marksdailyapple.com/prebiotics/#axzz2Pro4Cv7k) accessed 8 April, 2013
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- Gibson, G. R., Scott, K. P., Rastall, R. A., Tuohy, K. M., Hotchkiss, A., Dubert-Ferrandon, A., et al. (2010). Dietary prebiotics: current status and new definition. Food Science & Technology Bulletin: Functional Foods, 7(1), 1–19. doi:10.1616/1476-2137.15880
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