When, more than two thousand years ago, the Latin poet Horace immortalised in his “Satires” his habitual dinner of lagane (forerunners of lasagne), chickpeas and leeks, he was unaware that he had preserved for posterity the first menu friendly to the intestinal microbiota. Imagine a community of over 100 trillion micro-organisms, 10 times the number of our cells, with a genome over 100 times larger than ours. Such is the gut microbiota and it consists of all the microorganisms that habitually populate our intestines, finding in us the perfect host. It accompanies us from birth, grows with us and is shaped by our lifestyle and dietary habits. And, if we treat it well, learn to listen to it and communicate with it through food, it keeps us healthy and slows down ageing.
Good bacteria and bad bacteria: the biodiversity in the gut that (also) communicates with the brain
Although science has been decoding it for some 20 years, the gut microbiota has only recently become a “hot topic” of research: over 20,000 mentions in the last 12 months on PubMed reveal new evidence on how important it is to live in harmony with this community of some five thousand species, including bacteria and fungi, that affects our entire organism.
The gut microbiota keeps us healthy and is the control room for many functions and aspects of our body: it modulates the metabolism of the food we ingest, synthesises vitamins such as B12, vitamin K and folate, teaches the immune system to distinguish friend from foe, defends us from dangerous microorganisms and produces 70% of our serotonin, a hormone that is essential for intestinal motility.
It has been called the “feel-good hormone”, reminding us that there is an axis between the gut and the brain, with a highly developed neural network. The gut-brain axis is bi-directional: the microbiota has the ability to release neurotransmitters that are crucial for the regulation of the sleep-wake cycle and mood, and it can be altered by anxiety and stress. The microbiota of depressed individuals is characterised by the loss of beneficial bacteria such as bifidus bacteria. Loss of beneficial strains is also associated with chronic inflammatory bowel disorders such as Crohn’s disease.
Can the microbiota slow (or accelerate) ageing?
The microbiota grows, becomes adult and ages along with its host, and its health status can either accelerate or slow down the ageing process. With advancing age, the abundance and variety of microbes decreases. It has been demonstrated that alterations in the gut microbial population and changes in
intestinal permeability may directly contribute to the condition of chronic low-grade inflammation, or ‘inflammaging’, that characterises ageing and affects, among other things, mental and physical well-being, metabolic abnormalities and infections.
Poor intestinal motility, difficulty in chewing and swallowing, lack of appetite: experts affirm that this metabolic-physiological decline can be slowed down and better counterbalanced through a series of dietary behaviours that influence the composition and functionality of the intestinal microbiota. As always, prevention is key, with interventions to promote the growth and development of “good” bacteria, such as short-chain fatty acid producers. These, among other things, support the homeostasis of the immune system, increase intestinal impermeability, provide the body with energy, and regulate appetite and sleep.
The consequences of a “poor” gut microbiota
If it is true that we are what we eat, this applies even more to our microbiota. Nutrition shapes and changes the structure of the gut microbiota, for better… and for worse.
A poor diet, stress, a sedentary lifestyle change and weaken the biodiversity in the gut, which may manifest itself it in a lack of beneficial or protective species, competition between species, or the proliferation of potentially pathogenic strains that we have unwittingly encouraged. These factors can disrupt the balance of the microbiota, depleting it. This condition is thought to affect 25% of the population. And so some “neglected” microorganisms, unable to find nourishment in the food we ingest, may resort to the intestinal mucus, making it more vulnerable; other species may bypass the epithelial cells and the vascular barrier and reach internal organs and adipose tissue, causing chronic inflammation, the root cause of many conditions and metabolic diseases, such as cardiovascular disease, obesity, diabetes and cancer.
Improving the gut microbiota with the Mediterranean diet
If the microbiota is happy, we are too because brain and gut talk to each other. And they share a passion for good food. But how should we nourish the microbiota?
There is no one solution. There is no life-saving food. The answer resides in a series of habits and lifestyles that can make a difference in the long run, and the key word is variety. A limited diet will reward one family of bacteria at the expense of others. So the conditions are created to disrupt the microbiota and trigger inflammation. One thing is certain. High-protein diets do not help the “good” bacteria in the microbiota to thrive: a study by the Genome Institute of Singapore conducted on overweight or obese adults on a four-week keto diet showed a decrease in the microbiota’s bifidobacteria that promote gut regularity and function. On the other hand, science has demonstrated the benefits of the Mediterranean diet on the gut microbiota: a study published in Gut and conducted on subjects with a habitually low consumption of fruit and vegetables and a sedentary lifestyle, showed that following the Mediterranean diet for 8 weeks improved the composition of the gut microbiota, reducing inflammation.
These findings confirm some earlier Italian research(a study published in BMJ Gut) according to which plant-based diets such as the Mediterranean diet are associated with a healthy microbiome, leading to an increase in the levels of short-chain fatty acids that break down fibre.
Pasta, the microbiota loves its starch… and the vegetables we serve it with
The microbiota loves the Mediterranean diet because of the fibre contained in many of its foods, such as whole grains, fresh and dried fruit, which nourish the good bacteria in our gut. Our body does not have the enzymes to use them to advantage, but the bacteria do. And the bacteria are also able to digest for us the starch in pasta, which has a similar molecular structure to fibre.
If pasta is then incorporated into a Mediterranean dietary model, the microbiota’s well-being increases exponentially: a study published in BMJ Gut examined 612 subjects aged 65 to 79 years from France, Italy, the Netherlands, Poland and the UK, subjecting half of the sample to a diet based on the Mediterranean diet for one year. By the end of the study, their gut microbiota had changed for the better, inhibiting the production of inflammatory chemicals that can lead to loss of cognitive function and the development of chronic diseases such as diabetes, cancer and atherosclerosis. In other words, the Mediterranean diet improves cognitive function and promotes healthy ageing.
Pasta & Co: meet the friends of the microbiota
Fibre should never be missing from the menu of the gut microbiota. Soluble (pasta al dente) and insoluble (vegetables) fibre stimulate the production and expansion of good bacteria. And that’s not all. Polyphenolic compounds, abundant in berries, citrus fruits, cabbage, broccoli, tomatoes, olive oil, and nuts, are associated with the growth of Lactobacillus and Bifidobacterium; artichokes, asparagus, garlic, onions, leeks, Jerusalem artichokes and chicory are important for their inulin content; legumes such as beans, lentils, chickpeas, peas and broad beans for their Fructo-oligosaccharide and Galacto-oligosaccharide content; pine nuts, hazelnuts, spinach and oily fish for omega-3 fatty acids… all foods that combat chronic inflammation.
Speaking of pasta, with the arrival of summer, eating it cold can give the microbiota an extra boost: the resistant starch in pasta changes its structure with temperature variations and behaves exactly like fibre, which is then used by the bacteria to produce a short-chain fatty acid called butyrate, which controls intestinal permeability.
Pasta, vegetables, legumes: so we come round again to Horace’s pasta with chickpeas and vegetables. But also – for a more “modern” take – pasta with tomato sauce or pesto…
