Probiotics Review (Including Kombucha and Pet Supplements)
Initial Posting: 4/14/2018 Last Update: 9/7/19
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There is such a variety of probiotic products available for purchase that choosing one can be difficult. To help, we suggest that you first check our Results
table to find identify products "Approved" for quality in our testing. Then consider the following:
- Choose a product that contains the type(s) of probiotic organism(s) shown to work for your condition. See the "What They Do" section as well as the summary table "Uses of Probiotics in People" below for the type of probiotic that suits your needs and then check the Results table for products which contain that/those organism(s).
- Make sure the product provides an adequate number of cells per daily dose, i.e., an amount that has been shown to work. There can be huge variation from product to product. Among products tested, the total number of cells per daily serving ranged from just 100 million to 1.8 trillion! Typically, an adult probiotic should provide at least 1 billion cells daily — although, as discussed in the "What They Do" section, some probiotics have been shown to work at a lower dose.
- Compare prices. The last column in the Results table below shows the daily cost based on suggested serving sizes. The most expensive products per daily dose tended to provide larger amounts of organisms (50 to 900 billion per day), while lower cost products tended to provide smaller amounts -- but this isn't always the case.
- Cautions. If you have a milk allergy, be aware that trace amounts of milk proteins may occur in some probiotics (See Concerns and Cautions).
For some of the most common uses of probiotics, see our Top Picks
Kombucha and Probiotic Drinks
Sizable numbers of cells (1 to 2 billion per cup) were found in two kombucha drinks and one probiotic drink. We chose one of the kombuchas as our Top Pick
in this category. None of the drinks were found to be contaminated with heavy metals or pathogenic microorganisms.
What They Are:
Probiotic products consist of viable (live) bacteria and/or yeasts that confer a health benefit. Probiotics are available in varied forms such as yogurt and other cultured milk foods, capsules, tablets, beverages, and powders. Probiotics should not be confused with prebiotics, which are complex sugars (such as inulin and other fructo-oligosaccharides) that are ingested as fuel for bacteria already present in the gastrointestinal tract. Prebiotics and probiotics are sometimes combined in the same product and termed synbiotics.
Although not included in this current Review, in 2015, ConsumerLab tested three popular kefir (cultured milk) products (Evolve, Lifeway, and Latta) and found huge amounts of live cells per cup (respectively, 950 billion, 250 billion, and 150 billion cells). Interestingly, although people with lactose intolerance are often advised to consumer kefir instead of milk, all the kefirs contained lactose, ranging from 8.2 to 12.7 grams per cup, nearly as much as in milk. However, enzymes from the bacteria in kefir may help breakdown lactose in the digestive tract.
Kombucha is a probiotic beverage produced by fermenting sweetened black or green tea with bacteria and yeast. Depending on the type of tea, sugar, and starter bacteria and yeast used, the resulting liquid contains varying amounts and types of bacteria and yeast, tea catechins (such as epigallocatechin gallate i.e. EGCG), organic acids (including acetic, lactic and gluconic acid), caffeine, sugars (sucrose, lactose, glucose, and fructose) and small amounts of ethanol (alcohol), amino acids, vitamins and minerals (Greenwalt J Food Proct 2000).
As a result of fermentation, kombucha is naturally lightly carbonated with a slightly vinegary taste. Fruit juices and/or spices and other ingredients may be added for flavor or to provide the sugar that is fermented. (See What to Consider When Buying and Using).
The starter culture of yeast and bacteria used to ferment the tea is called a SCOBY (symbiotic culture of bacteria and yeast), Medusomyces gisevi, or "mother" (a term also used to describe the culture in apple cider vinegar). Due to the mushroom-like shape and brown color of the SCOBY, pieces of which may remain in the liquid after processing, kombucha is also referred to as "mushroom tea."
(For the clinical evidence regarding kombucha see the end of the next section).
What They Do:
The normal human gastrointestinal tract contains hundreds of different species of bacteria, referred to as intestinal flora. When the normal balance of these bacteria is disturbed by illness or antibiotic treatment, the most common effect is diarrhea. Probiotics were originally thought to work by re-colonizing the small intestine and crowding out disease-causing bacteria, thereby restoring balance to the intestinal flora. However, research is showing that probiotics are more likely to act in other ways, such as producing substances that inhibit disease-causing bacteria, competing for nutrients with them, stimulating the body's own immune system and interacting with nervous system present in the gut.
For example, a U.S. government-funded study with Lactobacillus GG (Culturelle), showed that giving older, healthy individuals a capsule with 10 billion cells twice a day for 28 days caused no significant change in the composition of the intestinal flora but appeared to modulate bacterial activity in ways which could promote interactions with the gut lining and anti-inflammatory pathways. When retested a month after treatment ceased, the effects were no longer present — indicating that the probiotic was only effective during and/or shortly after administration (Eloe-Fadrosh, Mbio 2015). An analysis which looked at this and seven other studies of probiotics concluded that there is "a lack of evidence" as to "whether or not there is an effect of probiotics on the fecal microbiota composition in healthy adults" (Kristensen, Genome Medicine, 2016). It is important to note that this analysis (funded in-part by an unrestricted grant from the controlling entity of the pharmaceutical company Novo Nordisk A/S) assessed only the bacterial composition of feces and not the effects of probiotics in the gut itself or in the treatment or prevention of disease, i.e., it is not a commentary on the clinical effects of probiotics. A study that used endoscopy to take samples directly from within the intestines found that, after taking a multi-strain probiotic (providing 25 billion cells) twice daily for two months, only 2 of the 10 participants had significant colonization in the gut, and four had moderate colonization. The researchers concluded that colonization does not occur in everyone who takes probiotics and may depend on factors such genetic and immune system differences (Zmora, Cell 2018).
A variety of probiotic organisms (alone or in combination) have been tested in clinical trials for a range of conditions. Here are some of the most notable findings by condition: