Can this really be true?

Well, two recent studies seem to suggest exactly this.

There are over 10 times as many microorganisms co-inhabiting the human body than there are actual human cells. At any given time there are over 100 trillion foreign organisms living in the intestines alongside our cells. This relationship between the ‘gut biome’ (the total population of bacteria) and human cells is believed to be mutualistic; where both parties benefit from each other’s presence. This fact really makes one question what it means to be ‘human’ if we are made of more bacteria than animal cells, then what does that make us?

But let’s not ponder existentialist questions right now. The take-away message here is that bacteria outnumber us in our own body and that’s pretty amazing and obviously important.

Increased diversity of healthy gut flora correlates with decreased obesity

Recent studies in both animal models and humans have come to the tentative conclusion that increased diversity in ‘healthy’ gut flora was linked to a decreased incidence of obesity and related cardiovascular problems.

Researchers in Denmark revealed that the bacterial populations lining your gut wall could in fact be a key in controlling the obesity epidemic. In their study, researchers found that subjects who had an increased population of diverse flora in their gut had decreased body mass indices (BMI – a measure of obesity) and were also at a lower risk for cardiovascular disease. They analysed the presence of bacterial DNA (the ‘microbiome’) of all subjects and found a higher incidence of bacterial diversity in those subjects who were not obese. The results were published in the journal Nature in August 2013.

Another study performed in rodents, published in the journal Science, recently found that if a rat was transplanted with the gut flora of a healthy, lean human, they showed a greater tendency to not put on weight, when compared with rats who had received the transplant from an obese person. In the latter case, when the rats were fed high fat diets, they showed a greater propensity to put on weight. However not all bacteria in the gut will promote a lean physique. Quite on the contrary actually. In one study French researchers showed that an increase in the presence of bacterial lipopolysaccharides (LPS) in the gut is perhaps counter-intuitively, also linked to obesity and diabetes. LPS are up-regulated during an infection with gram-negative bacteria (gram negative bacteria like Shigella or Salmonella – bacteria that are pathogenic and not-at-all ‘friendly’ – as evidenced by the diarrhoea you experience when infected by them – NB ‘gram negative’ refers to a particular staining test that identifies specific bacteria.)

Probiotics may not be the magic bullet, but supplementing with them can help

So if these elegant experiments are anything to go by, the conclusion here is that we should all be monitoring our gut flora and promoting growth of healthy bacterial populations in order to maintain a healthy weight and metabolism. Eating healthy food will promote a healthy gut. It’s as simple as that. Yet, furthermore, supplementing your diet with ‘friendly' probiotic supplements (e.g. Lactobacillus and Bifidobacterium being two species of ‘friendly’ healthy bacteria) will help promote a healthy digestive tract as well as out-compete the harmful bacteria for space – hereby creating a friendly environment for your cells as well as a hostile environment for the nasty bugs that may make you sick and in turn, promote weight gain.

Some health professionals may advise antibiotics to control the harmful bacteria; the downside to this approach is that these antibiotic agents are non-specific and will eliminate most if not all bacteria in the gut (friendly as well as pathogenic.) A bit like shooting yourself in the foot to remove pain from gout.

Supplementing with probiotics may be the safest way forward here, see it as a preventative measure as opposed to reactionary. Additionally, environmental exposure to microorganisms is a strong determinant in the composition of your gut flora. This has been evidenced by families having a very similar (if not identical) composition of bacterial organisms living in their gut.

Ultimately we should praise our tiny helpful friends whose subletting of our gastrointestinal space as their abode has helped us not only be healthier, but also decrease the likelihood of us putting on weight.

So, let’s all hail the friendly bacteria shall we. They are literally the best friends we may have and on top of the fact that they may help prevent you from putting on excess weight, they also influence us psychologically, hence the intestinal triumvirate of truth, repeat after me:

Healthy gut = Healthy mind = Healthy waistline

by Christopher von Roy BSc, MSc, DCP Immunology


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Do you supplement with probiotics? If so, have you noticed a difference to your metabolism?