With a growth rate of 1.5 percent in 15 years, in 2014 Italian vegetarians and vegans are about 4 million, according to Eurispes report. Vegetarians avoid eating meat, while vegans follow a stricter regime with the absence not only of meats, but also of products originated from animals. After centuries of omnivorous diet, may these new habits have consequences or benefits for our body?
Inside the human guts, there is a huge microbial ecosystem. The interest around human intestinal or oral microbiota, namely the commensal bacteria that we house in our guts, has quickly increased over the last years: in fact, the number of Pubmed cited publications about this topic has raised from 80 issues in 2000 to 2,700 in 2013. The reason lies in the involvement of gut bacteria in different physiological or pathological conditions, ranging from energy regulation, cognitive processes and immunity trade-off.
Despite the big number of studies about microbiota, “there are few observational studies considering the faecal and salivary microbiota, and metabolome of individuals subjected to different dietary habits since long time ago”, said Marco Gobbetti, leader of Diet4MicroGut, an Italian project arisen to investigate the bacterial flora susceptibility to diet, and the relationship between microbiota alteration and state of well-being. Since nutrients for humans are nourishing able to affect the growth and balance of native microbes, an impaired diet may imbalance the gut flora and, as Gobetti explained, “we still don’t know if the genetic heritage may be (and to what extent) a lifeline towards a wrong diet”. In fact, other studies are based on the effects of rapid and intense change of the dietary habits, and alterations of the human intestinal and salivary microbiota over a short time has been already observed.
In order to study how the omnivore, vegetarian and vegan diets may affect the oral intake of microorganims, and the composition of the oral and faecal microbiota, the research has been addressed to a large number of individuals (about 50 for each dietary condition), recruited in various Italian regions. “It's the first time that a microbiota research has been addressed to such a large number of individuals”, said Gobetti and his words are confirmed by the inclusion of the Italian study in the U.S. clinical trials list. Dietary habits registration and biological sample collection covered three weeks, then samples have been analysed in ten Italian research centres, joined in a unique effort to build up a permanent European platform for such type of studies.
Researchers are analysing samples with a huge variety of techniques: bacteria will be recognized and characterized for their antibiotic resistance, for DNA sequences and functional activities, and for metabolomics traits, with the aim to determine representative populations of the three types of diet. Diet4MicroGut has started in 2013 and it will go on until 2016. The first results are about the salivary microbiota. Analysis from the Ercolini's laboratories at Federico II University in Naples confirmed that dietary habits seem to slightly influence the microbial composition and only in part the metabolome. “The faecal microbiota could represent another issue and we hope to get some consistent results within the next months”, said Gobbetti.
The interest for Gobbetti's group research is strengthen by some new findings. Cathryn Nagler has recently published a paper on PNAS, underlying the role of gastrointestinal bacteria in allergic response to food. The absence of specific bacteria could be detrimental for some immunological reactions responsible for allergies. In addition, the author suggested that an ultimate solution could be the allergy process interruption by manipulating the microbiota. Moreover, the Martin Blaser paper, appeared on Cell, showed how microbiota alterations are related to obesity and how could be important to restore the balanced gut population. Finally, another study published on Nature compared the Italian diet with that of African hunter-gatherers Hadza, confirming how diet could influence guts populations but also health: for instance, Hadza do not suffer from colon related diseases. Starting from these premises, it could be interesting to assess if different diet are able to restore or conserve guts flora.
Gobbetti’s team research is destined to rise: “we are already involved in a European joint project initiative (ENPADASI) that aims to establish a European network among research groups working on diet and human body responses in health and disease states”. Gobbetti also highlighted the possibility to go on under Horizon 2020. Effectively the Grand Societal Challenge of Horizon 2020 also includes the issue of food impact in human health.
Certainly, understanding diet effects may be an instrument to favour a stable and healthy oral and intestinal microbiota, which is able to prevent diseases and guarantee human longevity.