Are tacos gut-friendly? Study unlocks potential functional profile of Mexican staple

By Stephen Daniells contact

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© Getty Images / MarieKazPhoto
© Getty Images / MarieKazPhoto
The combination of corn tortilla and common beans known as taco may boost the production of beneficial short chain fatty acids in the gut, according to a new study.

Data obtained using the in vitro​ colonic Simulator of Human Microbial Ecosystem (SHIME) indicated that the combination of corn “tortilla” (Zea mays​ L.) and common beans (Phaseolus vulgaris​ L.) led to increases in the Bifidobacteria​, and decreases in Lactobacilli​ and Clostridium​ spp.

The data also revealed that levels of the short chain fatty acid (SCFA) acetate increased after three days of fermentation in the simulator, while ammonia levels also decreased, which the researchers noted was a potentially significant finding.

“Ammonia is a key product of metabolic pathways in many organisms, encountered frequently at the crossroads of catabolism and anabolism and their production may be the result of total digestion of tissue proteins by less specific microbial proteinases,” ​explained the researchers in the journal Food Research International​.  

“Frequently, the reason for this toxicity may be a consequence of the molecule’s ability to protonate and deprotonate rapidly, forming molecular species with very different lipophilic charges. Hence, the decrease during the treatment in ammonium ion production was a positive result because high concentrations of this metabolic product could act as a tumor cancer promotor in colon.”

Study details

Scientists from the Tecnológico Nacional de México/Instituto Tecnológico de Tepic (Mexico), UNESP – Univ  Estadual Paulista (Brazil), and the University of São Paulo (Brazil) used SHIME to study the effects of tacos in a model intestinal system. SHIME has previously been described as an “extensively validated as a valuable in vitro tool to study intestinal digestion and fermentation under representative conditions in a long-term study setting”​.

The simulator was allowed to stabilize for two weeks and then fed 50 g of beans and 50 g of tortilla mixed with 100 mL of carbohydrate based medium every day for nine days. Samples were collected every three days.

Results showed that the production of the SCFA was higher during the taco ‘feeding’ period compared to pre-taco period in the three sections colon. Acetate was produced in higher concentrations than propionate and butyrate, said the researchers.

Ammonia ions were also reduced in the three simulated colon vessels, they added.

“Mexican “taco” showed a possible potential functional profile of an ancestral staple food due to the production of SCFA and the decrease in ammonium ion concentrations during its fermentation,” ​wrote the researchers.

“In order to improve our knowledge of the effects in gut microbiota metabolism of the colonic fermentation of cooked food (even the preparation method could influence during the fermentation) as eaten (mixturing protein, carbohydrates, fiber, bioactive compounds) and the possible effects in host health of gut metabolites, combination of ​in vitro and ​in vivo studies are needed,”​ they concluded.

Source: Food Research International
Published online ahead of print, doi: 10.1016/j.foodres.2018.05.072
“In vitro colonic fermentation of Mexican “taco” from corn-tortilla and black beans in a Simulator of Human Microbial Ecosystem (SHIME) system”
Authors: A.P. Cárdenas-Castro, et al.