FOOD NUTRITION: GUT HEALTH
Diagram
Live microbes, and the food that feeds them
Probiotic
Live microorganisms, usually bacteria, added to food so they reach the gut alive and give a health benefit.
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Prebiotic
A food ingredient, usually a fibre, that is not digested by us but is fermented by gut bacteria, feeding the good microbes.
Figure 1: Probiotics are live bacteria, while prebiotics are fibres that feed gut bacteria. Drawn in our own style from the probiotic and prebiotic discussion in Charalampopoulos and Rastall, Prebiotics and Probiotics Science and Technology.
Introduction
Probiotic and prebiotic are both sold for gut health, and the words sound alike, but they are different things. A probiotic is a live microorganism, usually a bacterium, that is added to a food in numbers high enough to reach the gut alive and give a health benefit. A prebiotic is not a microbe at all: it is a food ingredient, usually a fibre such as inulin or fructo-oligosaccharides, that the human gut cannot digest but the gut bacteria can ferment, so it feeds the microbes already living in the gut. One adds microbes, the other feeds them.
Quick comparison
Table 1: Probiotic compared with Prebiotic
| Aspect | Probiotic | Prebiotic |
|---|---|---|
| What it is | Live microorganisms, usually bacteria | A food ingredient, usually a fibre |
| Alive | Yes, it must reach the gut alive | No, it is not alive |
| Examples | Lactobacillus and Bifidobacterium strains in yogurt and fermented milk | Inulin, fructo-oligosaccharides and galacto-oligosaccharides |
| How it works | The live microbes settle in the gut and give a benefit | Gut bacteria ferment it, so the good microbes grow |
| Digested by us | It is a microbe, not a nutrient to digest | No, it passes undigested to the colon |
| Fermented in the gut | The microbes themselves may ferment food | Yes, gut bacteria ferment it |
| Found in | Yogurt, fermented milks, probiotic drinks and supplements | Onions, garlic, chicory root, bananas, oats and added fibres |
| Needs a dose | Yes, enough live cells must survive to the gut | Yes, enough must reach the colon to feed the bacteria |
| Storage | Needs care: heat and time kill live microbes | Stable, because it is not alive |
| Effect on gut bacteria | Adds new microbes | Feeds the microbes already there |
Scientific explanation
Definition
A probiotic is a live microorganism which, when taken in adequate amounts, gives a health benefit to the host, usually by reaching the gut alive. A prebiotic is a food ingredient that is not digested in the upper gut but is selectively fermented by gut bacteria, so it feeds beneficial microbes and supports their growth.
Working principle
A probiotic works by surviving the acid of the stomach and the bile of the small intestine, reaching the colon alive, and then acting there: it can crowd out unwanted microbes, help the gut barrier, and interact with the immune system. The strain matters, because the benefit belongs to a named strain, not to the species in general. A prebiotic works differently: it passes through the stomach and small intestine undigested, reaches the colon, and is fermented by the resident bacteria, especially bifidobacteria. Fermentation feeds those bacteria so they grow, and it produces short chain fatty acids in the gut.
Apparatus
The books used here name no laboratory apparatus for measuring or comparing either term, so no apparatus list is given.
Measurement procedure
The books used here give no standard laboratory procedure with volumes and steps for either term, so no procedure is invented here.
Factors affecting readings
For probiotics, the strain, the dose of live cells, and the storage decide the effect: heat, air and time kill live microbes, so a yogurt kept warm loses its live count. For prebiotics, the type of fibre and the dose decide the effect: different fibres feed different bacteria, and too much at once can cause gas and discomfort. The books used here give no dose numbers, so none are stated.
Formulas and calculations
The books used here give no formula for either term, so no formula is given here.
Industrial applications
- Probiotic: yogurt and fermented milks, where live cultures are the product.
- Probiotic: probiotic drinks and supplements, where a named strain is given in a dose.
- Prebiotic: chicory root fibre and inulin added to foods to feed gut bacteria.
- Prebiotic: infant foods and drinks with added galacto-oligosaccharides.
- Both together: synbiotic foods, where a probiotic and a prebiotic are combined in one product.
Advantages and limitations
- Probiotic, advantage: it adds live microbes directly, so the benefit does not depend on the microbes already present.
- Probiotic, limitation: the microbes must survive the stomach and storage alive, and the benefit belongs to the named strain, not to any yogurt.
- Prebiotic, advantage: it is stable in storage and in cooking, because it is not alive, and it feeds the good microbes already in the gut.
- Prebiotic, limitation: it only works if the right bacteria are already present to ferment it, and a large dose can cause gas.
FAQ
What is the difference between a probiotic and a prebiotic?
A probiotic is a live microbe added to food, while a prebiotic is a fibre that feeds the gut bacteria already present.
Is yogurt a probiotic or a prebiotic?
Yogurt with live cultures is a probiotic food. Plain yogurt with no live cultures is not.
What foods are prebiotic?
Onions, garlic, chicory root, bananas and oats, and foods with added inulin or fructo-oligosaccharides.
Can you take both together?
Yes. A food with both is called synbiotic: the prebiotic feeds the probiotic as well as the resident microbes.
Does cooking destroy them?
Heat kills live probiotic microbes, but prebiotic fibres are stable in cooking.
References and further reading
- Charalampopoulos, Dimitris and Robert A. Rastall (eds). Prebiotics and Probiotics Science and Technology. Springer, 2009.
- Tamang, J. P. and K. Kailasapathy. Fermented Foods and Beverages of the World. CRC Press, 2010, chapter Probiotic and Prebiotic Fermented Foods, p. 377.
- Google Books pages read for this article:
- Charalampopoulos, Dimitris and Robert A. Rastall (eds). Prebiotics and Probiotics Science and Technology. Springer, 2009 (Google Books page read)
