Q: Is wine fermented with native yeast good for my gut microbiome?—Michel, Paris
A: Moderate drinking has been linked to a range of digestive health effects, including potential benefits to the gut microbiota. Scientists are still trying to understand how the trillions (yes, trillions!) of microorganisms that make up the gut microbiome impact our health, but it’s clear that gastrointestinal well-being may impact inflammation, cardiovascular disease and more. With rising interest in how diet affects the gut microbiome, it makes sense to wonder if certain types of wine—particularly those made with native vs. commercial yeasts—may carry more benefits than others.
What Are Native Yeasts?
Yeasts are single-celled fungal organisms that convert sugar to ethyl alcohol and carbon dioxide. They also produce a range of other compounds, many of which contribute to the flavors and aromas of wine. While there are many types of yeast, the species crucial for wine (as well as beer, other alcoholic beverages and leavened bread) is called Saccharomyces cerevisiae.
Native yeasts—also known as indigenous, ambient or wild yeasts—are the yeasts naturally present in a vineyard. They’re found on grape skins at harvest, on cellar equipment and elsewhere, and they’re part of the naturally occurring microbial community of a place. Some winemakers feel that using native yeasts contributes to a richer, more authentic expression of terroir. However, wild fermentations can be unpredictable and difficult to manage, especially when producing wine on a large scale.
What Are Commercial Yeasts?
In many cases, winemakers choose to inoculate their fermentations with commercial yeast. Commercial yeast contains particular strains of S. cerevisiae that produce desired effects during fermentation. Commercial yeast are more predictable than wild yeast, which can sometimes produce slow (or even ‘stuck’) fermentations, off flavors and aromas, and other undesired traits. Commercial yeasts, on the other hand, have been selected to produce particular flavors and aromas and reliable, efficient fermentations. They’re usually more active than wild yeasts and will typically ‘take over’ a fermentation from any wild yeasts present.
Both commercial and wild yeast typically result in a fermentation dominated by S. cerevisiae. While other types of yeast exist in nature on grapes, those yeasts are usually active only in the initial stages of fermentation. Since S. cerevisiae tends to be more resistant to alcohol than other species of wild yeast found on grapes, it tends to eventually dominate even native fermentations. So when winemakers talk about wild and commercial yeasts, they’re effectively talking about the same species of microorganism—just different strains.
Yeast and the Gut Microbiome
Do those different strains of yeast impact the gut microbiome in different ways? Dr. David Mills, a distinguished professor in the department of food science and technology at UC Davis, told Wine Spectator that there is a strain of S. cerevisiae called Saccharomyces boulardii that has been shown to have a probiotic effect in humans. In theory, this strain could be present in a wild fermentation. However, even if S. boulardii were present in a finished wine, it would be dead or inactive—and, Mills says, “generally probiotics by definition need to be alive.”
Wines that are fined and filtered will probably have most yeast material removed, and any residual yeasts that remain will almost certainly be dead. Even if native yeasts had gut health benefits over commercial yeasts, they likely wouldn’t be able to deliver them in a finished wine—and you’d have to drink much, much more than would be recommended (or even possible!) to see any benefit.
Mills adds that overall, a “more indigenous or diverse [yeast] population” is unlikely to carry any special benefits. “There's just no data to support that.” He also emphasizes that wine delivers extremely small quantities of yeast, yeast material and other potentially beneficial microbes. And again, most or all of the microbes in finished wine are dead or inactive, whether from alcohol itself or the addition of sulfur dioxide (sulfites) at bottling.
Does Wine Have Other Gut Health Benefits?
All that said, there’s some evidence that a portion of wine’s fiber content—which, though modest, may benefit digestive health—comes from yeast cell walls left in the finished wine. And beyond yeast, wine contains many other compounds, particularly polyphenols, that are metabolized by the gut microbiota in ways that seem to benefit overall health.
What about the potential digestive health effects of natural, orange and low-sulfur wines? Read our next Health Q&A to find out!
As always, talk to your healthcare provider about incorporating wine into a healthy lifestyle.—Kenny Martin
