Scientists assert that there is no standard method to assess overall diet and multiple approaches are currently used to examine dietary patterns.
However, they postulate that individual dietary components may not be the most suitable barometer for personalised nutrition as “current dietary recommendations have shifted from individual foods/nutrients to eating patterns as a whole” and should be adapted to current eating habits “to promote greater adherence”.
To test their hypothesis, the team compared individual dietary features (such as fibre and protein) before and after food consumption and identified specific dietary patterns “best associated” with gut microbiome diversity.
Among these, ‘prudent’ plant-based and flexitarian diets exhibited the highest Healthy Eating Index (HEI) scores while Western-like diets were associated with lower gut microbiome diversity and ‘exclusion’ diets with low relative abundance of healthy Bifidobacterium bacteria.
The authors explain that these dietary patterns had a greater effect on Bifidobacterium abundance than age and gastrointestinal disorders (such as IBS and gluten intolerance): “This reinforces that overall diet is a main factor affecting the Bifidobacterium relative abundance in US adults,” they said.
Conditions for microbe abundance
Five dietary patterns were identified as being most associated with gut microbiome: two Western-like (health-conscious and standard) diets, two ‘prudent’ (plant-based and flexitarian), and one exclusion diet (low-carbohydrate).
The most pronounced difference observed was the depletion of Bifidobacterium in participants adopting the exclusion diet (ED), who self-reported more gastronintestinal (GI) disorders and appeared to follow a lower-carbohydrate diet with less grains and, as such, gluten.
The authors write: “Exclusion of gluten and carbohydrates, such as fermentable oligo, di-, and mono-saccharides and polyols, in order to alleviate GI symptoms, has been previously associated with a lower abundance of Bifidobacterium.”
This was supported by further analysis that indicated “lower percentage of carbohydrates and higher percentage of fats in the ED pattern were both contributors to this association, but not exclusive ones”.
Positive association with prudent diets
Plant-based (PB) diets comprising lots of fruit, vegetables and wholegrain cereals promoted Bifidobacterium abundance, which is consistent with other research, say the authors.
“This supports the hypothesis that plant protein might be a potential but currently underexplored contributor of the beneficial effects of plant-based products on gut microbiota”, they write.
Adherence to prudent-like diets, and especially PB, was also linked to a higher abundance of Oribacterium and lower abundance of Parabacteroides.
They assert that other studies have determined that Parabacteroides is low or absent in vegetarian diets compared to non-vegetarian diets but increases after resistant starch intake and with high adherence to a Mediterranean diet.
Participants in the PB group were associated with the highest dietary fibre intake and had the best chance of adhering to official dietary guidelines.
Those following the FL diet (consisted mainly of fruit, wholegrain cereal, and nuts) were slightly older than participants in the other groups but demonstrated the best overall diet quality and high gut microbiota diversity, compared to the typical Western-like diet.
Overall, it was determined that participants following dietary regimes rich in plant-based food exhibited higher gut microbiota diversity than typical Western-like diets, characterised by processed, sweetened foods and low vegetable intake. The Standard Western diet, in particular, exhibited the poorest diet quality and lowest HEI score.
The results demonstrate that a global approach is more efficient in explaining variations in gut microbiota than single nutrient/food data, the authors say, although larger studies on more diverse populations would help reinforce and enhance our understanding of the interactions between diet and microbiome.
Source: Oxford University Press
First published online: doi.org/10.1093/ajcn/nqab332
‘A posteriori dietary patterns better explain variations of the gut microbiome than individual markers in the American Gut Project’
Aurélie Cotillard et al.