Gut Bifidobacterium decrease with age: from infancy to elderly

2022-05-10

A balanced gut microbiome has a significant impact on immunity, metabolism, and trophic function. When our gut health loses its equilibrium and dysbiosis occurs, harmful bacteria can thrive, increasing the risk of developing a range of diseases. Among the vast gut bacterial community are Bifidobacterium spp., a beneficial bacteria that regulate the intestinal immunity and play a significant role in the protection of the intestinal barrier.

Studies have shown that people with celiac disease, obesity, diabetes, allergic asthma and dermatitis have lower levels of Bifidobacterium in the gut compared to healthy people.

The proportion of Bifidobacterium-dominated gut microbiomes in infants decreases with age, from childhood to old age.

 

Infanthood:

The establishment of the gut microbiota was initially considered to occur at birth. Recently, microorganisms were observed in the placenta and amniotic fluid, suggesting a primary fetal colonization. Change in gut microbiota composition stabilizes around the first and second years of life, and by the third year adult-like microbiota develops.

Bifidobacterium are the most abundant genus present in the early weeks of a healthy infant gut. They play an important role in the breakdown of human milk oligosaccharides (HMOs) , stimulating the immune system and decreasing intestinal permeability (known as ‘leaky gut’). However, the initial colonization by bifidobacteria is dependent on a number of extrinsic factors, such as in the mother’s vaginal tract, breast milk, placenta and amniotic fluid. Birth mode in particular has a significant impact on this initial colonization.

A study reveals that the full-term infant gut has been correlated with much higher levels of Bifidobacterium (which benefit the immune system) and Bacteroides (which assist in the breaking down of food and produce valuable nutrients and energy that the body needs); these tend to be dominant in the early weeks of life, whereas the pre-term infant gut tends to be dominated by pathogenic bacteria such as Proteobacteria, Clostridium and Staphylococcus, and have been associated with lower levels of beneficial bacterial such as Actinobacteria.

 

Adulthood:

Diet plays a significant role in shaping the gut microbiome. The westernized diet (characterised by a ‘high intake of sugar, animal protein and fat, but low intake of fibre’ diet) has led to a marked decrease in beneficial Bifidobacterium and Eubacterium species, which is associated with a breach in the mucosal barrier, otherwise known as ‘leaky gut’. During adulthood, the levels of bifidobacteria are considerably lower (2-14% relative abundance), and not only does the number of bifidobacteria decrease with age, but the microbial diversity is reduced.

 

Elderly:

Bifidobacterium levels further decrease in old age due to the aging process, evidenced by changes in the gastrointestinal tract and immunosenescence. Antibiotics medication is an essential medical tool in the elderly, yet its unavoidable negative effect on the elderly microbiota composition decreases bifidobacterial population.

Bifidobacteria is extremely important for our health. One of its main functions is to digest dietary fiber and other complex carbs the body cannot digest on its own. This process produces other important chemicals such as short chain fatty acids, conjugated linoleic acid (CLA) and bacteriocins to reduce the risk of diabetes, heart disease and other chronic disorders.

 

References:

Collado, M. C., Rautava, S., Aakko, J., Isolauri, E., and Salminen, S. (2016). Human gut colonisation may be initiated in utero by distinct microbial communities in the placenta and amniotic fluid. Sci. Rep. 6, 23129. doi: 10.1038/srep23129

Dominguez-Bello, M. G., Costello, E. K., Contreras, M., Magris, M., Hidalgo, G., Fierer, N., et al. (2010). Delivery mode shapes the acquisition and structure of the initial microbiota across multiple body habitats in newborns. Proc. Natl. Acad. Sci. U.S.A. 107, 11971–11975. doi: 10.1073/pnas.1002601107