That “gut feeling” you sometimes get may be more literal than you think: research continues to reveal the importance of the bacteria in our digestive tract, called the “gut microbiome.” This symbiotic population of microbes affects health and well-being in often unexpected ways. The microbiome sends signals to the central nervous system, regulates inflammation, even influences cardiovascular health. Wine’s impact on health appears to depend significantly on the microbiome, and we are now learning that it may not actually be the constituents of wine that make it healthy for us; it is the things that the microbiome transforms them into.
How wine promotes a healthy microbiome
Wine’s relationship with the microbiome is a two-way street: Recent studies demonstrate how wine consumption influences the composition of the various bacteria, while other research demonstrates how the microbiome metabolizes wine into components that boost the immune system.The idea that wine’s health benefits may not derive directly from what’s in it is revolutionary, and it is re-jiggering the field of nutrition and aging. For nearly 200 years we have gone by the words of the famous 19th century gastronome Anthelme Brillat-Savarin, who wrote “Tell me what you eat, and I will tell you what you are,” but that is turning out to be only half right, at least in the physiologic sense.
How the microbiome enhances the health effects of wine
Here’s how it works: wine encourages a healthy microbiome, which returns the favor by enhancing what is called bioavailability, the absorption and transport to the tissue where the active ingredient or nutrient in a food or drug is to have an effect. Wine’s effects are attributed to its antioxidant polyphenols, but their poor absorption gives them low bioavailability. This is one reason why effects in tissue cultures and lab studies don’t predict what happens in people: you can’t get the same levels in the target organ as you can in cells in a Petri dish. But think of a healthy microbiome as a sort of Amazon Prime for wine: it metabolizes wine polyphenols into compounds that are taken up and delivered, rapidly and often in a more potent form.
An elegant example of this was published by researchers from Washington University School of Medicine, who detailed how this phenomenon helps wine fight influenza. They showed how flavonoids, a class of immune-boosting polyphenols present in red wine, are altered by a specific type of bacterium in the colon into a molecule called DAT. This in turn signals the production of the immune modulator interferon, which then enhanced the survival of mice inoculated with the flu virus. Inflammation in the lungs was correspondingly lessened as well.
Similar examples abound for a variety of diseases. One study demonstrated wine’s influence on gut bacteria in obese subjects with a condition called metabolic syndrome. After a period of regular wine consumption, strains of bacteria known as “intestinal barrier protectors” proliferated, while those producing markers of inflammation diminished. So if “you are what you eat,” in the updated interpretation of Brillat-Savarin’s maxim, you are equally what you drink, and with wine all the better for it.
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 The microbial metabolite desaminotyrosine protects from influenza through type I interferon. Steed AL,, Christophi G, Kaiko GE, Sun L, Goodwin VM, Jain U, Esaulova E, Artyomov MN, Morales DJ, Holtzman MJ, Boon ACM, Lenschow DJ, Stappenbeck TS. Science. 2017 Aug 4;357(6350):498-502.
 Red wine polyphenols modulate fecal microbiota and reduce markers of the metabolic syndrome in obese patients. Moreno-Indias I, Sánchez-Alcoholado L, Pérez-Martínez P, Andrés-Lacueva C, Cardona F, Tinahones F, Queipo-Ortuño MI. Food Funct. 2016 Apr;7(4):1775-87.