Each individual owns a unique gut microbiota profile that plays many specific functions in the host’s nutrient metabolism, maintenance of the immune system, and protection against pathogens. The gut microbiota is composed of different bacteria. Each human’s gut microbiota is shaped in the early stages of life as its composition depends on infant transitions (birth gestational date, type of delivery, methods of milk feeding, weaning period) and external factors such as antibiotic use.
These personal gut microbiotas remain relatively stable in adulthood but differ between individuals due to enterotypes, body mass index (BMI) level, exercise frequency, lifestyle, cultural and dietary habits, and even their habitat.
There is no unique optimal gut microbiota composition since it is different for each individual. However, a healthy host–microorganism balance must be maintained in order to optimally perform metabolic and immune functions and prevent certain diseases. Studies show that more than 20,000 metabolic functions in humans are influenced by the human microbiome. Dysbiosis of gut microbiota is associated not only with intestinal disorders but also with numerous extra-intestinal diseases such as metabolic and neurological disorders. Understanding the cause or consequence of these gut microbiota establishes a balance between health and disease, and also helps to maintain or restore a healthy gut microbiota composition that is useful in developing promising therapeutic interventions.
FACTORS THAT CAN ALTER A HEALTHY GUT MICROBIOTA.
1. Early stages: it all starts with pregnancy, type of delivery, and methods of milk feeding.
After birth, a rich and dynamic ecosystem develops from factors like the mother’s skin, vaginal and fecal microbiota, and the environment the microbiota is in contact with. Microbiota colonization varies according to the type of delivery as well.
With regards to vaginal delivery, newborns acquire a microbiota composition resembling their mother’s vaginal microbiota, consisting mostly of lactobacillus and Bifidobacterium. And infants born by cesarean section (C-section) acquire bacteria derived from the hospital environment and the mother’s skin, like Staphylococcus. Cesarean birth has been associated with an increased risk of chronic immune disorders such as asthma, systemic connective tissue disorders, juvenile arthritis, inflammatory bowel disease, and obesity, but certainly, after one year of birth, microbiota from both newborns are usually similar.
Regardless of the method of milk feeding, breastfed infants generally get a more complex and diverse Bifidobacterium microbiota than formula-fed. Their microbiota also has a higher richness and diversity of Bifidobacterium, and a lower number of Clostridium difficile, and Escherichia coli than formula-fed infants.
2. BMI (Body Mass Index).
Studies show that there is a presence of gut dysbiosis (lack of balance diversity in the bacteria community) in patients with obesity. Bacterial signaling pathways may influence host physiology and induce or maintain obesity. Gut bacteria participate in pathophysiological processes, like insulin resistance, fat storage increase, inflammation, and appetite dysregulation leading to excess body fat. Therefore, it is necessary to maintain optimal body weight and body composition in order to maintain an optimal and healthy gut microbiota and vice versa.
3. Lack of Physical activity.
Daily exercise increases gut microbial diversity which may increase the resistance of the intestinal barrier, reduce mucosal permeability, and inhibit inflammatory substances, besides helping with appetite control. Evidence suggests that different signaling molecules produced by a gut microorganism can activate some receptors in the brain area, that are important for mood and behavior. Therefore, especially during the juvenile period, exercise and gut microbiota represent important factors that promote both brain and metabolic development.
Lack of sleep and interrupted sleep is associated with gut dysbiosis, which may be due to disruption of the circadian rhythms. Metabolic changes associated with lack of sleep may in fact be mediated through the overgrowth of specific gut bacteria. Likewise, the end products of bacterial species which grow in response to sleep loss are able to induce fatigue, insulin resistance, obesity, and appetite dysregulation.
5. High chronic response to stress.
The gut microbiota has been found related to a variety of stress-related conditions including anxiety, depression, and irritable bowel syndrome. Stress exposure in the early stages of life or in adulthood can change the organism's microbiota. Microbial populations might also shape an organism's stress responsiveness leading to all of the metabolic consequences mentioned above. Hence, finding strategies to get down the chronic stress response is the key to restoring optimal bacterial diversity and reducing the symptoms derived from stress.
Western diet is characterized by a high intake of energy-dense and processed food, and a high intake of fat, sugar, additives, and sweeteners. In comparison to such calorie-dense foods, there is a very low intake of fiber-rich foods, fruits, and vegetables. This imbalanced diet becomes a risk factor for many chronic diseases including diabetes and obesity. This kind of Western diet is related to inflammation, which affects healthy gut bacteria diversity. To date, there is no reliable testing of the effects of food additives on gut microbiota available. Even though some food additives can be beneficial for human health, there are others that may alter the composition of the microbiota and lead to gut inflammation, which may promote inflammatory diseases and food intolerances.
The recommendation would be to follow a diet rich in vegetables, fruits, resistant starches, good quality protein sources (such as blue fish, and white meat), healthy fats, and an occasional intake of no processed red meat. In short, the Mediterranean diet pattern would be optimal to create a healthy gut microbiota diversity.
7. Other factors to keep in consideration.
Sun exposure, quality of the social environment, meditation, a flexible mindset, and consciousness of having a good lifestyle can contribute to maintaining a healthy gut microbiota that is beneficial for health and disease prevention.