Frequently Asked Questions & Consumer Information

Consumer Information

Consumer guidelines for probioticsand prebiotics prepared by International Scientific Association for Probiotics and Prebiotics

Frequently Asked Questions

Q. Do we naturally harbor probiotics in our bodies?

We naturally harbor many potentially beneficial bacteria. Probiotic bacteria are frequently, but not always, chosen among these normal colonizers of humans. Sometimes the term “probiotic” is used as a synonym to “commensal, beneficial bacteria”, but this is an incorrect usage. Commensal microbes may be beneficial, but until they are isolated, characterized and shown in human studies to impart a health benefit, they cannot be accurately called “probiotic.”

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Q. What is a recommended dose? Is more always better?

No general recommendation can be made. The dose must be based on studies which show an effect. Effective levels range widely, depending on the strains and the clinical target. Some products are effective at 50 million; others recommend over 1 trillion live cells per day. The important thing to know is that different probiotics have been shown to be effective at different levels and a product containing a higher number of live probiotics may not be better than one with fewer.

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Q. Is daily consumption necessary?

Frequency of administration should follow what was used in the human study showing the health effect. Since most published human studies have used daily consumption, this is typically what is recommended. In some cases, multiple times per day may be recommended.

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Q. Are refrigerated products best?

In general, microbes survive better at lower temperatures. However, technologies for keeping probiotics alive at room temperature have been developed by product manufacturers. It is not necessarily the case that refrigerated products will be superior to those that are not refrigerated. Choose products from reputable companies that are labelled for viability “through the end of shelf life” and not “at time of manufacture”.

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Q. To be good, does a probiotic need to be isolated from a human?

Researchers have hypothesized that a probiotic isolated from a human has properties that make it better able to function in a human. This is still a topic being researched. We do know that (1) bacteria that are native to one person are foreign to another, and (2) probiotics, even ones isolated from humans, do not seem to colonize long term. We also know that there are several probiotic strains that were not isolated from humans that have been shown to have health benefits (such as strains of Bifidobacterium animalis subsp. lactis). So more important than source of isolation of the probiotic is if human studies have shown it to be effective when it is administered.

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Q. Do all probiotics function in the same way?

No. Probiotics are described by their genus (e.g., Lactobacillus), their species (e.g.,rhamnosus) and their strain (e.g., GG). This degree of specificity in describing a probiotic is essential since functions can be strain-specific. For example, Lactobacillus rhamnosus GG may have different effects from L. rhamnosus GR-1. The strongest recommendation is for probiotics that are supported by strain-specific research.

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Q. Many probiotic yogurts and other food products contain added sugar. Does this negate any health benefits from probiotics?

There is no evidence that the sugar added to sweetened yogurt negates the health benefits associated with the probiotics contained in the yogurt. Sugar is digested and absorbed in the small intestine and would not be expected to interfere with microbial effects farther down the intestinal tract. However, studies comparing identical probiotic products with and without added sugar have not been conducted. When choosing probiotic foods, these foods should be part of a balanced diet. There can be negative consequences of consuming an unbalanced diet.

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Q. Are probiotics still alive if they are dried?

If bacteria are dried and stabilized properly, they remain alive (although dormant) and start to grow again after they reach the moist environment inside your body.

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Q. What is the difference between live active cultures and probiotics?

Live cultures are microbes associated with foods, often as food fermentation agents. Many of these have not been directly tested for health benefits. Probiotics are live microbes that have been shown to have a health effect. Also, some probiotics are microbes that would not typically be associated with foods (such as E. coli), and as such would not typically be referred to as “live cultures.”

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Q. What information should product manufacturers provide for their probiotic products?

The following information should be available on the product label or accompanying website:

  • Identification of the genus, species and strain of each probiotic present in the product
  • Assurance that the product contains the level indicated on the label of each probiotic strain in the product through the end of shelf life
  • Indication of the health benefit(s) associated with the product, including citations for published human studies have been conducted on the product or the specific strains in the product
  • Contact information for the company
  • Product information website
  • Proper storage conditions
  • Recommended usage based on the level shown to be effective in the published studies


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Q. Which probiotic is the best one?

This depends on many factors. Not all probiotics are the same. Different strains of even the same species are not necessarily the same, and different commercial probiotics have been studied for different effects. Furthermore, each person has unique colonizing microbes, host genetics, diet and medication usage, and therefore each person has the potential to respond to probiotics differently. So choose a probiotic that is made by a reputable company, that has been tested for the effects that you are interested in, that is in a format that is appealing to you and that you find works for you.

Product recommendations can be found at:

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Q. Can products containing live bacteria that have not been tested in human studies still be effective?

Some companies know very little about the specific health effects of the bacteria they are selling. These products should not be called “probiotics,” since probiotics by definition must be shown to have health effects. Scientific studies are expensive to conduct, and not all companies sponsor them. If studies have not been conducted on a strain, it is not known if the strain can survive and function as a probiotic in the human body. A strain that has not been studied for human health effects might be effective. But such a product, in general, cannot be strongly recommended. It is best to purchase a product made by a trustworthy company that can provide documentation of the health effects important to you.

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Q. Are probiotics better when you get them from foods or from pills?

Probiotics from either foods or pills can be effective. The important consideration is that you are getting high enough numbers of a strain or combination of strains that have been tested for efficacy and works for you. Food sources of probiotics have the advantage in that they can offer good nutrition along with the probiotic bacteria. Supplements can be more convenient for some people and may provide higher levels of probiotic, depending on the specific products.

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Q. Can dead bacteria be probiotics?

No. Probiotics by definition must be alive when administered. Some publications have suggested that dead bacteria can have positive physiological effects. In fact, there are commercial products that specifically are comprised of dead bacteria. However, such products are not probiotics. The number of studies on dead bacteria are quite few and it is unlikely that dead bacteria could mediate the many positive effects demonstrated by live, probiotic bacteria.

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