In recent weeks, you may have noticed some familiar headlines about red wine and cardiovascular health. Why the sudden return of these stories? Because of an article recently published in the American Journal of Clinical Nutrition.
Funded in part by a grant from the São Paulo Research Foundation (FAPESP), the "Wine Flora Study" was carried out by prominent researchers from institutions in South America, Europe, and the United States: University of São Paulo, Brazil; State University of Campinas, Campinas, São Paulo, Brazil; University of Brasília, Brasília, Federal District, Brazil; University of Verona, Verona, Veneto, Italy; Austrian Institute of Technology, Tulln, Lower Austria, Austria; and Harvard Medical School, Boston, Massachusetts. The team looked into the effects of red wine on gut flora and plasma levels of trimethylamine- N -oxide (TMAO). And what they found was quite interesting.
The Study
Previous results, such as those reported in a 2019 Medscape article, have pointed to the beneficial effect that red wine has on the gut microbiome.
The Wine Flora Study involved 42 men (average age, 60 years) with documented coronary artery disease. The trial encompassed two 3-week interventions. In one, the participants consumed 250 mL of red wine per day; the red wine sample had an alcohol content (% v) of 12.75. The Brazilian Wine Institute produced and supplied the red wine: a 2014 Merlot bottled in August 2016 and customized for the study. The second intervention involved alcohol abstention.
Each intervention was preceded by a 2-week washout period. Because certain foods and drinks could interfere with the results, the participants were instructed not to consume alcoholic beverages, fermented foods (yogurt, kombucha, soy lecithin, kefir, sauerkraut, and other fermented vegetables), synthetic prebiotics (insulin, fructooligosaccharides), fiber, dairy, food polyphenols (grapes, grape juice, cranberries, strawberries), and probiotics.
At each intervention, the gut microbiota was analyzed via 16S rRNA high‑throughput sequencing. This method makes it possible to identify bacterial species. The plasma metabolome of 20 randomly selected participants was evaluated by ultra‑high‑performance LC–MS/MS. In this method, liquid chromatography separates the compounds, and a mass spectrometer is used to analyze them.
One of the metabolites of interest was TMAO, which is produced from the trimethylamine released when gut bacteria process protein-rich foods. TMAO has been identified as playing a role in the development of atherosclerosis.
Results
After red wine consumption, there was significant remodeling of the gut microbiota, with a difference in beta diversity and predominance of Parasutterella, Ruminococcaceae, several Bacteroides species, and Prevotella.
Plasma metabolomic analysis revealed significant changes in metabolites after red wine consumption, consistent with improved redox homeostasis, which is involved in the oxidative stress that promotes atherosclerosis.
Plasma TMAO, however, did not differ between red wine intervention and alcohol abstention.
Implications
The researchers concluded that modulation of the gut microbiota may contribute to the putative cardiovascular benefits of moderate red wine consumption. But, as they were careful to point out in the very title of the study, a red wine intervention does not modify plasma TMAO. They also mentioned that the 3-week period may have been too short for the findings to serve as the basis for promoting any meaningful modification. In addition, the team emphasized that these data remain hypothesis‑generating and pave the way for future research.
In an interview with FAPESP, the study's corresponding author, Protásio Lemos da Luz, MD, PhD, warned about the risks associated with drinking too much alcohol (>8.5 oz., or 250 mL, of wine daily).
It should be kept in mind that, in Brazil, people do not drink nearly as much wine as they do beer or liquor. Furthermore, the evidence that is available does not provide confirmation of the existence or the extent of the protective health effects associated with light or moderate alcohol intake.