Published in the Journal of Agricultural and Food Chemistry, the Spanish researchers investigated the impact diet had on microbiota – specifically looking at fibers and polyphenols.
Findings showed that white bread was the main food source of soluble hemicellulose in the diet and a product positively related to higher Lactobacillus levels in the gut – “probably the most novel finding in our study”, the researchers said.
“To date, the prebiotic effect of cereals has been traditionally attributed to whole grain foods because of their high fiber content. However, our results reveal that the consumption of refined grains, often undervalued in this regard, could beneficially modulate intestinal microbiota,” they wrote.
The findings were of great interest, they said, as refined foods like white bread were widely consumed in Western societies.
The researchers suggested the promotion of Lactobacillus levels could be a result of the hemicellulose content (dietary fiber) and resistant starch content in white bread. Although, they added it was difficult to ascertain how much resistant starch came from the food itself.
They noted that it was possible the promotion of increased Lactobacillus levels could be down to other foods typically consumed with bread, although added they had not found such association between any of these foodstuffs and gut microbiota.
Full diet research important in gut health
The study also found flavanones and pectins from orange lowered B. coccoides and C. leptum feces.
In light of the findings, the researchers said future gut health research needed to focus on broad diet rather than isolated compounds because the diet-microbiota interrelationship was far more complex than the impact of single compounds.
“Most research about diet and intestinal microbiota has been traditionally focused on the effect of single food components (usually soluble fibers) acting as prebiotics to promote the growth of some beneficial bacterial groups, such as Lactobacillus or Bifidobacterium,” they wrote.
The study involved 37 health adults – 27 females and 11 males aged between 56 and 57 years old.
The participants were assessed using a semiquantitative food frequency questionnaire that included 160 food items. Each were asked, item by item, what foods they usually ate and the levels they consumed and fecal samples assessed for nutrient composition.
Source: Journal of Agricultural and Food Chemistry
2014, Volume 63 (23), pages 5330-5336. Doi: 10.1021/jf501546a
“Pilot Study of Diet and Microbiota: Interactive Associations of Fibers and Polyphenols with Human Intestinal Bacteria”
Authors: A. Cuervo, L. Valdés, N. Salazar, CG. De los Reyes-Gavilán, P. Ruas-Madiedo, M. Gueimonde and S. González