Substitutive Effects of Milk vs. Vegetable Milk on the Human Gut Microbiota and Implications for Human Health

Background: In the last two decades, the consumption of plant-based dairy substitutes in place of animal-based milk has increased in different geographic regions of the world. Dairy substitutes of vegetable origin have a quantitative composition of macronutrients such as animal milk, although the composition of carbohydrates, proteins and fats, as well as bioactive components, is completely different from that of animal milk. Many milk components have been shown to have relevant effects on the intestinal microbiota. Methods: Therefore, the aim of this review is to compare the effects obtained by previous works on the composition of the gut microbiota after the ingestion of animal milk and/or vegetable beverages. Results: In general, the results obtained in the included studies were very positive for animal milk intake. Thus, we found an increase in gut microbiota richness and diversity, increase in the production of short-chain fatty acids, and beneficial microbes such as Bifidobacterium, lactobacilli, Akkermansia, Lachnospiraceae or Blautia. In other cases, we found a significant decrease in potential harmful bacteria such as Proteobacteria, Erysipelotrichaceae, Desulfovibrionaceae or Clostridium perfingens after animal-origin milk intake. Vegetable beverages have also generally produced positive results in the gut microbiota such as the increase in the relative presence of lactobacilli, Bifidobacterium or Blautia. However, we also found some potential negative results, such as increases in the presence of potential pathogens such as Enterobacteriaceae, Salmonella and Fusobacterium. Conclusions: From the perspective of their effects on the intestinal microbiota, milks of animal origin appear to be more beneficial for human health than their vegetable substitutes. These different effects on the intestinal microbiota should be considered in those cases where the replacement of animal milks by vegetable substitutes is recommended.