Can experiments detect differences that matter?
- This question is very significant because experiments seem to find differences in bacteria diversity amongst obese and healthy individuals. But the question is how significant are those differences? There is great diversity amongst healthy individuals bacteria itself, and there isn’t an established “healthy” microbiome that all others can be compared to. Microbiomes vary from person to person. So, do the differences between obese and healthy person microbiomes even matter if there are already established differences from person to person? Being able to label a specific difference in the microbiome as causational for a disease isn’t possible if there isn’t even an established and well-characterized network to compare it to.
Does the study show causation or correlation?
- When interpreting scientific literature this is a very important question to consider. While the results may show a correlation between a certain microbe and outcome, it can not be labeled causal until the reverse causational relationship is explored. If a journal states a microbe causes an outcome/disease, they must be sure to rule out the disease or outcome isn’t causing the presence of the bacteria. Additionally, Microbes could be mere bystanders during certain outcomes and just measuring whether they are present or not does not allow for the relationship to be named causational. The literature must have real proof of causational relationships by providing mechanisms of action. This leads to the next question to consider.
What is the mechanism?
- This question is very significant in evaluating scientific literature. Without evidence of the mechanism, the relationship can merely only be correlational. Observing the correlation between microbes and certain outcomes is a step in proving a causal relationship. But, the mechanism behind how microbes can cause certain outcomes is ultimately the best evidence of labeling the relationship as causational. By conducting experiments that rule out certain taxas and confounding factors, allows researchers to pinpoint whether a certain microbe affects human health and then study how it does so.
How much do experiments reflect reality?
- The significance of this question lies within the methods and conduction of the experiment. It seems that in many experimental studies the setting is so fabricated and unrealistic that their findings may be worthless. If researchers are implanting germ-free mice with microbes and observing what happens to them, they are completely ignoring other factors and creating a very unrealistic setting. No person is going to be “germ-free” such as these mice, so the results of the experiment might not even be applicable if they can’t repeat such results in a human.
Could anything else explain the results?
- When studying the microbiome, it would be foolish to think that bacteria cause outcomes without any other contributing factors. Diet is a very important factor that researchers seem to neglect when conducting an experiment. They transplant microbes into mice, observe reduced fat, and publish all these articles that people can lose weight with a fecal transplant. The media then takes these reports and blows them up even further, all without taking into consideration one’s diet and how that could influence the gut microbiota rather than a transplant.
I think the most helpful question when discussing controversy is the mechanism of action. Like I said before, you can observe relationships between microbes and outcomes but that observation only provides evidence for correlation. Knowing the mechanism and explaining it provides a piece of whole new evidence for a side of the controversy. If one side can only support their claim with correlations while the other actually has a real mechanism of action, then the side with a mechanism explanation is much easier to believe. The mechanism can actually explain and support their thesis, which is why I think it the most important thing to consider when discussing a controversy.
