The latest research in this area all point to the same conclusions. Diet, stress and genetics have an immense impact on the microorganisms that reside in our digestive tract, and this has a direct relationship to disease states and health .
Our dietary choices have one of the biggest impacts on our gut microbiota and the research in this area is abundant. The issue is that due to the large complexity of the microbiota itself and the research on this topic, deriving any useful conclusion remains difficult.
How strong is the impact of diet?
Experiments on mice have shown that a change from a low fat diet rich in plant polysaccharides to a typical Western diet (high in fat and sugar) triggered change in the microbial composition after just 1 day.
Carbohydrates seems to have one of the biggest influences of the microbiota composition. This is primarily because every singly day roughly 20g-60g of dietary carbohydrates reach the colon undigested (by enzymes) [2, 3], becoming a prime energy source for the residing microbial communities. And it has been documented that changing the amount and/or type of carbohydrate for the duration as little as 4 weeks can have a drastic impact on the microbiota composition [4, 5, 6].
Overall, the research suggest that insoluble fiber is one of the most beneficial dietary components for a healthy intestinal microbiota. A high intake of insoluble fiber has been associated with reduced carcinogenic enzyme concentrations, improved glucose tolerance, a reduction in negative effects caused by high fat and high protein consumption, improved short chain fatty acid production and reduction of inflammatory markers [7, 8, 9]
It is estimated that every single day roughly 12-18g of protein reach the human colon. And increasing the amount and quality of protein has a direct impact on the amount reaching the gut undigested. . Studies show that higher dietary protein consumption has been linked to greater DNA damage in colonic mucosa (particularly when levels of fermentable carbohydrates are low), improved formation of beneficial short chain fatty acids, and increased production of gases and metabolites [10, 11].
Fat gets a ton of blame for a variety of metabolism disorders and microbiota research supports these believes. In general, high fat diets have been shown to decrease the amount of short chain fatty acid production, increase inflammatory makers, increase intestinal permeability and reduce glucose tolerance [12, 13, 7].
Stress has also been shown to have significant affect on the gut microbiota and it’s affects are attributed to the biological communication occurring through the gut-brain axis. Research in this area suggests that stress has been shown to lower the amount of beneficial lactobacillus, increase intestinal permeability and modulate the mucosal immune response [14, 15]. However, because of the two-directional relationship (gut microbiota can influence ones ability to handle stress), the overall implications of this remain unclear.
Certain genes determine our ability to effectively digest certain nutrients such as carbohydrates . If we unknowingly step outside of our body’s ability to digest these nutrients by enzymes, they are passed into the colon and fermented by the bacteria that reside there. Opportunistic bacteria may take advantage of this and can disrupt the balance of the whole community of the colon.
This section reviewed some of the most important factors affecting the intestinal microbiota and presented some relevant research findings. Key points include:
- Diet, stress and genetics have a significant impact on the composition of the intestinal microbiota, with diet being the most influential
- The amount and type of carbohydrates in your diet appears to be one of the key dietary influencers and adjustments can cause rapid microbiota changes
- A high intake of insoluble fiber appears to be one of the most beneficial dietary influencers on the composition of the microbiota
- High protein and/or fat consumption has been linked to several negative effects, but their impact can be reduced by high fiber consumption
- The negative impact of stress has also been demonstrated, but due to the two-directional relationship it’s effect remains unclear
- Genetics influence the level and types of enzymes our digestive systems product and this influences which nutrients reach the colon undigested