Mental Indigestion

by Jim Caryl

Tag: microbiome

Your microbiome and you (part I): Gut

This post was chosen as an Editor's Selection for ResearchBlogging.orgYOU probably think that your body has things pretty much under control, being the finely evolved machine that it is, it knows where its at, and does a generally good job of looking after itself. You’d be right of course, but it doesn’t do this without a little help.

Some of this help comes in the form of your microbiome.

I have written previously about the exciting concept of the human microbiome in which I described how the number of bacterial cells on your body out number your own cells 10 to one, and asked to what degree you consider yourself to be human? The vast majority of these co-residents of you are organised into defined communities, the structure and diversity of which vary depending on where on the body they’re found: your mouth, your nose, various areas of your skin, your gut and urogenital tract. By understanding the interactions between each of these communities and our body, we can better understand their role in health and disease.*

In this the first of two posts on your microbiome, we’ll take a look at your gut.

The gut

probiotics-good-bacteriaMost people are undoubtedly familiar with the idea of ‘good bacteria’, in particular those of your gut, which we are encouraged to top-up on a daily basis with sickly sweet probiotic supplements containing various species of Lactococcus and/or Bifidobacterium. One can only imagine how on Earth we’ve coped throughout the course of evolutionary history without our daily supplement of Yakult.

The general scientific consensus on probiotics is that they don’t do any particular harm to most people, except perhaps your wallet, but occasionally the claims made by the manufacturers are often circumstantial, based on studies with poor methodologies, or are based solely upon observations from a petri dish or mouse model. Furthermore, when reliable evidence is documented, it is invariably for a very specific strain, thus there can be little confidence that is is a general property of the bacterial species as a whole.

Where the use of probiotics moves away from a general supplementation to being part of an active treatment for a condition, there is some evidence to suggest they may be of benefit, but on the whole, evidence is lacking and more research is certainly warranted. A Cochrane review (an international not-for-profit organization, providing up-to-date information about the effects of health care) in 2004, concluded:

“Probiotics appear to be a useful adjunct to rehydration therapy in treating acute, infectious diarrhoea in adults and children. More research is needed to inform the use of particular probiotic regimens in specific patient groups.”

However, in general there are insufficient data for the use of probiotics, over current standard therapies, in conditions such as eczema, Crohn’s disease, bacterial vaginosis and a slew of others. This is probably not helped by the fact that there is a good chance that the little pot of living bacterial joy you are consuming doesn’t actually contain any live bacteria of the type you think you’re getting.

A study published last month in the International Journal of Food Microbiology by an Italian team based the Istituto Superiore di Sanità in Rome, described a survey of such probiotics in Italy between 2005-6, seeking to identify and enumerate bacteria in commercially available supplements 1. A whopping 87% of samples showed evidence of not conforming to the Italian guidelines.

“Even though most labelled supplements (25 samples) indicated the presence of Bifidobacterium bifidum, this organism was only detected sporadically and always as dead cells.”

They also noted contaminants such as the food-poisoning pathogen Bacillus cereus, yikes.

Read the rest of this entry »

Bio suit…

HOW human do you think you are?

100% ?

90% ?

Well, let’s play a numbers game: in terms of cell numbers, you have in the order of a trillion cells in your body, though this value varies greatly between people and is constantly changing within each of us. However, you have some ten times this number of bacterial cells within (and on) your body 1. So at one level at least, you are only 10% human.

Of course, bacterial cells are quite a bit smaller than your cells, so there’s room for the both of you, in you.

bladder lactobacillus mouth1_scale_final
Images of human epithelial (tissue surface) cells coated with bacteria.

In terms of genes, the instructions that make you you, humans have about 30,000. Again, there are in the order of a hundred times this number of bacterial genes operating within and on your body 2. So at another level you are only 1% human.

Don’t worry though, of course you’re 100% human. Instead, we need to consider the extent of what being human actually is. Being human comes part and parcel with being a super-organism. We live in a symbiotic relationship with hundreds of different species of bacteria, without which we could not survive. Think of them as an invisible extension of your body’s innate defences, occupying every external surface, your skin, your gut, your eyes, ear, nose, and various other orifices.

There is mounting evidence to suggest that they influence our development; our physiology; our nutrition and metabolism; and immunity, where they play an important role from birth in educating our immune systems. They are your interactive suit of armour, both part of the environment and part of you. These communities of bacteria are referred to as the microbiome, and they are being investigated as part of the Human Microbiome Project, an effort by many research labs coordinated by the National Institute of Health.

Read the rest of this entry »