By Jeffrey Letourneau
A slew of recent articles claimed that certain strong beers, Belgian beers in particular, contain probiotic bacteria and improve gut health. These articles stemmed from a talk given by Professor Eric Claassen of Amsterdam University at a conference organized by Yakult Honsha, a Tokyo-based company that manufactures sweetened probiotic milk beverages. While consumers might find it tempting to believe that beer is a viable alternative to yogurt, neither scientific studies nor press releases have been cited by these articles. As a homebrewing microbiologist, I took a dive into the literature on beer to assess these claims.
Does beer contain probiotic bacteria?
Most beer is made with brewer’s yeast (Saccharomyces cerevisiae), which is a type of single-celled fungus, not bacteria. During fermentation, the yeast converts sugar in the original grain-water mixture (called the wort) into carbon dioxide and alcohol. This biological process is essentially what makes beer, beer. Contamination caused by bacteria can produce off flavors and prevent the yeast from doing its job, so conditions are kept sterile by boiling the wort and sanitizing all equipment prior to the addition of yeast. Hops are also commonly added to beer (IPAs are a particularly hoppy style, for example) both for the flavor they impart and for their antibacterial properties, which helps to further reduce the likelihood of contamination. As a result, yeast is the principal microbe present in beer, while bacteria are generally absent.
The next logical question is whether the yeast itself can act as a probiotic. According to the National Institutes of Health, probiotics are “live microorganisms that are intended to have health benefits when consumed or applied to the body.” Most commercially available beer is pasteurized and/or filtered, meaning that any live yeast or bacteria that were present are heat killed or excluded from the final product by the filter. Some craft beers, however, may be unfiltered and unpasteurized. If you’ve ever noticed sediment at the bottom of your glass, that was probably unfiltered yeast. In general, brewer’s yeast is not considered to be a probiotic. That said, the cell walls of yeast are rich in beta glucans, a prebiotic also found in mushrooms and cereals such as oats and barley. Prebiotics are compounds in food that promote the growth of beneficial gut microbes. Beta glucans in particular may enhance stress tolerance of the probiotic bacteria Lactobacillus, so there is a potential for modulation of gut health by beer yeast in that sense. Realistically, though, the impact is likely negligible since the prebiotic content of a beer will be much less than your favorite vegetable.
A relative of brewer’s yeast called S. cerevisiae var. boulardii has been used as a probiotic to treat conditions such as antibiotic-associated diarrhea and Clostridium difficile infection. Researchers have even explored fermenting with a mixed culture of brewer’s yeast and S. cerevisiae var. boulardii to enhance the health benefits of beer. Unfortunately, there is very little data out there on probiotic yeasts, and less still on their potential health benefits.
It’s worth mentioning that some beers are in fact made with bacteria, such as Belgian lambics and sour beers. Lambics use complex mixtures of bacteria and yeasts specific to the brewery. Bacteria used include Klebsiella, Enterobacter, Escherichia, Citrobacter, and yeasts include the genus Kluyveromyces. Sours commonly use Lactobacillus or Pediococcus and/or a type of yeast called Brettanomyces. Many probiotics actually come from the genus Lactobacillus, and in 2017, food scientists at the National University of Singapore created a new sour beer using the probiotic strain Lactobacillus paracasei L26. In current practice, however, bacteria are either killed by boiling after souring or out-competed by yeast and inhibited by the addition of hops, so it is unlikely that commercially available sour beers would exert a probiotic effect.
Does drinking a beer a day improve gut health?
We know that excessive alcohol intake negatively impacts the gut microbiome, leading to an overgrowth of bacteria in the intestines and changes in the microbiome composition such as increases in Proteobacteria. These alterations may lead to health issues such as increased permeability of the intestinal barrier and alcoholic liver disease. Overall, it is well documented in the literature that alcohol is not good for you.
Despite this knowledge, there is some evidence that low to moderate beer consumption may reduce the risk of cardiovascular disease, similar to effects observed for wine. While most of the calories in beer come from the alcohol or simple carbohydrates, beer does also contain nutrients such as B-complex vitamins derived from the fermentation of cereals and polyphenols. Polyphenols are a type of compound that may help explain the observed cardiovascular effects. Dietary polyphenols are understood to increase populations of beneficial gut bacteria.
In general, beer does not contain probiotics, although unfiltered beer can contain live organisms, and beers fermented with probiotic bacteria and yeast may become more widely available in the future. Low to moderate consumption of beer may have some positive health effects, perhaps mediated by the gut microbiome, but little research has been done in this area. By contrast, the negative effects of excessive alcohol consumption are abundantly clear. Overall, research into the effects of fermented foods and beverages on metabolism and the gut microbiome is still in its infancy, and there is much exciting work and continued research to be done by both brewers and biologists.
Peer-edited by Ryesa Mansoor