Polyphenols May Shield the Gut

Researchers in Spain have found that sulfites, a common preservative in wine, can alter the balance of gut bacteria during digestion. The study, published in the Journal of Agricultural and Food Chemistry, used laboratory models to simulate human digestion and examined how sulfites affect the gut microbiome when added to both synthetic wine and real red wine.

Sulfites are widely used in the wine industry to prevent spoilage and extend shelf life. However, some people report headaches or digestive discomfort after consuming products containing sulfites. To better understand the impact of these additives on gut health, scientists at the Institute of Food Science Research in Madrid designed an experiment using a three-stage digestion process that mimics the human gastrointestinal tract. They tested both synthetic wine and real red wine, with and without added sulfites at levels commonly found in commercial wines.

The research team collected fecal samples from three healthy adult volunteers to provide a source of gut bacteria. After passing the wine samples through simulated digestion and fermentation with these bacteria, they analyzed changes in the microbial community.

The results showed that adding sulfites to synthetic wine led to a decrease in several beneficial bacteria, such as Bacteroides and Ruminococcus, and an increase in bacteria associated with inflammation or negative health effects, including Escherichia/Shigella and Coprococcus. These changes were less pronounced in real red wine, which contains natural compounds called polyphenols. The researchers suggest that polyphenols may offer some protection against the disruptive effects of sulfites on gut bacteria.

The study also found that the impact of sulfites varied between individuals, depending on the unique composition of their gut microbiome. In some cases, the presence of sulfites led to a drop in commensal bacteria and a rise in potential pathogens or protein-degrading species. However, when sulfites were added to real red wine, these effects were generally milder or absent.

In addition to changes in bacterial populations, the researchers measured the production of short-chain fatty acids (SCFAs), which are important for gut health. They found that SCFA levels were generally higher after fermentation with red wine than with synthetic wine, regardless of sulfite content. The presence of sulfites sometimes increased or decreased SCFA production, depending on the individual’s microbiome.

The team also looked at how sulfites affected the metabolism of wine polyphenols during digestion. They observed that sulfite-treated red wine resulted in higher levels of certain polyphenol-derived metabolites in the colon, which may have implications for the bioavailability and health effects of these compounds.

The findings suggest that while sulfites can disrupt the balance of gut bacteria in laboratory models, the natural components of real wine may help buffer some of these effects. The researchers caution that their study was conducted in vitro, meaning outside the human body, and that more research is needed to confirm these results in people.

The use of sulfites in food and beverages is regulated in the United States and Europe, with maximum allowable levels set by authorities. Most people tolerate sulfites without problems, but a small percentage may experience adverse reactions.

This study adds to the ongoing debate about the health effects of food additives and highlights the complex interactions between diet, food processing, and the gut microbiome. The authors say their work could help inform future guidelines for winemaking and food safety, as well as provide new insights into how everyday foods and drinks influence digestive health.