Understanding the human body’s biggest microbiome

There are many probiotic products available. Probiotic bacteria can have unique properties, which may result in different health benefits. Health benefits are generally considered to be specific to individual bacterial strains, rather than to a genus or species as a whole.

For example, if a product is labeled with the genus and species Lacticaseibacillus rhamnosus (formerly Lactobacillus rhamnosus), we still don’t know the strain. Different strains of the same species may offer different health benefits, so identifying the specific strain is important when selecting a probiotic for a particular purpose.

A probiotic with more bacteria doesn’t necessarily equate to greater impact. Because their properties vary, some probiotic strains may provide health benefits at lower bacterial levels, while others require higher levels.

This means it’s important to choose a probiotic that’s scientifically associated with the preferred health benefit and to consume it according to recommendations. The amount required will depend on the strain and the associated health benefit.

Some probiotic products contain more than one strain, but this doesn’t automatically mean they provide greater benefits. Many multi-strain products have not been scientifically evaluated.

As with single-strain products, it can be helpful to look for scientific evidence supporting the strains and health benefits of interest.

Fermentation produces foods like yogurt, kombucha, sauerkraut and many others. The process involves live bacteria –– either naturally found in the food or added –– which transforms the raw material into a different food type, e.g. cabbage into sauerkraut or milk into yogurt.

The bacteria used for this are generally not probiotics. Additionally, fermented foods often go through further processing such as pasteurization, baking or filtering, which kills the live bacteria. To claim content of probiotics, the bacteria must be alive, have documented health benefits and be present in adequate amounts.

While all yogurts are made through fermentation, not all contain probiotics. The live bacteria used in most yogurts are primarily added for fermentation and are not generally considered probiotic strains with documented health benefits.

Probiotic yogurt contains specific live probiotic strains that are backed by science and have been shown to support a specific aspect of health. An adequate amount of the probiotic must also be present in the yogurt throughout the shelf life of the product.

Probiotic strains are bacterial strains with documented health benefits, as shown in human clinical studies. When choosing a probiotic, remember that the health benefits of one strain cannot be assumed for other probiotic strains, even within the same area of health.

Probiotic strains can be isolated from a variety of sources, including the human gut, the vagina, fermented foods and the environment.

The source from which a probiotic strain is isolated does not determine its health benefits. Instead, a probiotic’s properties and potential health benefits are determined by the specific strain and the scientific evidence supporting its use.

A probiotic strain does not need to be isolated from humans to provide health benefits.

Probiotic strains have been isolated from a variety of sources, including humans, foods, plants and animals. What matters is not where the strain came from, but whether it has been shown to be safe and provide health benefits in human clinical studies. This is supported by the International Scientific Association for Probiotics and Prebiotics (ISAPP), which states that a high-quality, effective probiotic does not have to be naturally found in the human gut or be human-derived.¹

Not necessarily. Humans are naturally exposed to microorganisms from a variety of sources throughout life, including other people, foods, pets and the wider environment², ³.

As a result, a probiotic strain is not necessarily more natural simply because it was originally isolated from a human source. What matters most is whether the strain has been shown to be safe and provide health benefits in scientific studies.