The microbiome is affected by many factors, with the biggest changes happening during the first years of life:
- Nutrition: Nutrition affects the microbiome from infancy – breast milk or formula, solids that are healthy and nutritious or solids that are processed. In the course of life, our diet affects the microbiome. As long as our nutrition provides materials that the bacteria can break down, these bacteria will continue to thrive and multiply, so the more varied the diet, the greater the variety of bacteria. Several studies show animals whose diets were different from those of their ancestors have microbiomes that adapted.
- Traditional Lifestyle Versus Modern Lifestyle: Societies that live in traditional ways (hunter-gatherers, traditional farming practices) have more diverse microbiomes than Western societies.
- Our Genetics: The degree of influence of genetics on microbiome composition is a subject that is frequently researched. In a study conducted in the United States and published in Cell magazine (2014), it was discovered that identical twins’ microbiomes will share more similarities than those of fraternal twins. In addition, there are groups of bacteria that may be inherited in groups with common ancestors.
- The Cleanliness of the Environment: It is hypothesized that an environment that is too clean creates immune deficiency and raises the risk of various allergies and autoimmune diseases (diseases in which the immune system attacks the body itself such as type 1 diabetes, celiac disease, inflammatory bowel disease, etc.). In an environment that is too clean, there are no harmful bacteria, but there are also no bacteria that can benefit us.
- Antibiotic Treatment: When we receive antibiotic treatment due to a bacterial infection or disease, the antibiotic kills the bacteria that caused the disease, but kills many other bacteria types too. In fact, the antibiotic erases much of the microbiome. After the treatment, the microbiome is restored to normal in most cases, but sometimes not entirely. It is impossible to know in advance how an individual will react, under what conditions, and why. It is also known that some bacteria can form a layer in the bowel walls (biofilm) and thus protect themselves from antibiotics.
- Additional Factors: Physical activity, sleep, stress, and smoking habits can all affect the microbiome.
Which Factor Affects Our Microbiome More: Genetics or Environment?
In a study conducted at the Weizmann Institute and published in the scientific journal “Nature” (2018), researchers examined 700 Israelis from different communities and found that the environment affects the microbiome composition more than genetics. Thus, there is more similarity between the microbiology of people who live in the same house and relatives who live in different homes. The researchers also found that ethnic origin does not affect the microbiome, but factors that are related to the environment such as the place of residence (whether urban or rural), lifestyle, nutrition, animal presence in the immediate vicinity, diseases in the past, and the use of antibiotics throughout the lifetime.