Capturing static and dynamic dietary patterns for human gut microbiome research: a conceptual framework

There is inconsistency in the evidence regarding the effects of food on the gut microbiome. These inconsistencies arise, in part, from substantial inter- and intraindividual variations in diet. The wide range of foods consumed directly influences substrate availability for the microbiota. By categorizing foods into broad groups and overlooking interactions among food constituents within individual foods, current dietary pattern approaches can obscure food-specific differences needed to understand dietary effects. Differences in habitual and occasional intake further complicate analyses since frequency of food consumption can produce different gut microbiota responses within the same individual. Flexible analytical approaches are needed to capture within-individual food intake frequency and food-specific effects. To address these challenges, this narrative review presents dietary pattern concepts that distinguish static (stable or consistent) and dynamic (fluctuating or episodic) intake of specific foods at the individual level. We performed a literature search in three databases, including Medline, CINAHL, and PsycINFO, to retrieve relevant articles that distinguish the concepts of "core foods" and "secondary foods" in population-level studies. We adapt these concepts to a microbiome context at the individual level and propose future directions for studies investigating the impact of diet on the gut microbiome.