Microbiome Dysbiosis

It is normal and healthy to have bacteria in the gut

A huge number of bacteria live in our guts. In fact, the average adult human is estimated to have 38 trillion (3.8 x 10¹³) bacteria living in their body, mainly in the digestive system. Ninety-seven percent of these bacteria are in the colon, whereas much lower numbers of bacteria are present in the stomach (10⁷ bacteria) and small intestine (10¹¹ bacteria).¹

These bacteria are referred to as the gut microbiome, which is made up of more than 5,000 different types of bacteria.² Together these bacteria produce a wealth of molecules as part of their metabolism, including vitamins, nutrients, and neurotransmitters.^3,4 These molecules are called metabolites. Some metabolites are able to get into the human intestinal lining where they have local effects,^5,6 while others enter the blood circulation and can affect organs such as the liver, or the brain.^4,7

Good health requires a balance between our diet, the microbiome and our gut

A close relationship between the diet and the composition of the microbiome determines the types of metabolites being produced in the gut.^3,8,9 A balanced relationship between diet, microbiome and human contributes to our well-being and long-term health.^10,11,12,13

In some circumstances, the natural balance, or homeostasis, in the gut may be disturbed resulting in an unbalanced, or dysbiotic, microbiome¹⁴ with loss of diversity, overactivity of certain types of bacteria, or growth of harmful bacteria.¹⁵ Ultimately this may have negative consequences on our own health.^16,17,18

Factors that may affect the balance of bacteria in your gut

Although the adult microbiome is relatively stable, it is sensitive to lifestyle factors such as diet,⁹ psychological stress,¹⁹ or medication.²⁰ Use of antibiotics, for example, may cause an imbalance in the microbiome, and this effect could be long-lasting.²¹

Potential ways to maintain a healthy microbiome

Studies have shown that some probiotics may help maintain a healthy balance in the microbiome and reduce the risk of antibiotic-associated diarrhea. In these studies, two particular types of probiotics, called Bifidobacterium, BB-12® and Lactobacillus acidophilus, LA-5®, helped to reduce the length of time people experienced antibiotic associated diarrhea.^22,23 One way that this may happen is when the probiotic bacteria compete with harmful bacteria, called pathogens, by producing substances that are toxic to these pathogens.^24,25 

Beyond this, there are a range of ways in which probiotics have been shown to support a balanced microbiome:

• Producing molecules with anti-bacterial effects, as shown by BB-12®,²⁴ LA-5®,²⁶ and Lactobacillus rhamnosus, LGG®²⁷
• Stimulating the body’s own anti-bacterial molecules, as shown by Lactobacillus paracasei, L. CASEI 431®²⁸
• Making it harder for pathogens to attach to the gut lining, as shown by BB-12®,²⁹ LGG®,³⁰ and Lactobacillus rhamnosus, GR-1®³¹ 
• Helping to physically displace adhering pathogens, as shown by LGG®³²

In conclusion, probiotics could help to support a healthy, balanced microbiome, particularly when imbalances occur due to lifestyle factors or medications such as antibiotics.

BB-12®, LA-5®, LGG®, L. CASEI 431®, and GR-1® are registered trademarks of Chr. Hansen A/S.

The article is provided for informational purposes regarding probiotics and is not meant to suggest that any substance referenced in the article is intended to diagnose, cure, mitigate, treat, or prevent any disease.