The gut microbiome is the most important force driving the evolution of dietary inflammation.
Humans have coevolved with commensal organisms and pathogens since our distant ancestors became multicellular. Today, our bodies are a habitat for a multitude of microbes and viruses, the majority of which inhabit the gut, making up a community known as the microbiome. It turns out that these microbes number as many as 100 trillion, and the sum of their genes outnumber human genes by a ratio of more than ten to one. Thus, for as long as humans and our predecessors have been eating, we have shared the food we eat with the bacteria in our guts.
Nutrients have Jekyll and Hyde characteristics on the microbiome, and are sometimes helpful and sometimes harmful. Those nutrients that enhance the barrier function of the gut and prevent pathogen colonization and growth have evolved a signaling function that is thrifty, reducing the costs of an immune defense. Nutrients that impair the barrier function of the gut and increase the risk of pathogen colonization and invasion have the opposite effects. Melissa Franklin and Chris Kuzawa and I compiled evidence from studies showing that inflammatory signaling by nutrients compensates for the effects they have on the gut microbiome.
Since 2012 even more evidence suggests that the immune effects of nutrients matches their influence on the microbiome. Lucky for us, some of the foods that kill pathogens and pathobionts and promote beneficial microbes are some of the tastiest: coffee, chocolate, many fruits and the healthy fats found in the Mediterranean diet.
Results of a recent study on the effects of chocolate matched our predictions exactly: decreased immune investment with nutrients that inhibit pathogens and promote protective species. Less IgA production accompanied beneficial changes in microbiome production with cacao feeding.
Cacao reduced fecal IgA
Closed circles represent the control diet, triangles and open circle are cacao/polyphenol diets.
From the paper: “In general, cocoa diets inhibited the growth of Staphylococcus, Streptococcus, and Clostridium histolyticum/C. perfringens (belonging to the Firmicutes phylum) produced by age.”
Our 2012 paper, Nutrient signaling: evolutionary origins of the immune-modulating effects of dietary fat. is available in this previous post.
Reference: Massot-Cladera, Malen, et al. Impact of cocoa polyphenol extracts on the immune system and microbiota in two strains of young rats. British Journal of Nutrition 112.12 (2014): 1944-1954.