The Gut Microbes of African Hunter-Gatherers

The Gut Microbes of African Hunter-Gatherers
wired.com

In westerners, Bifidumbacterium is a microbe that many nutrition scientists thought was essential to good gut health, but it is almost completely absent in the foragers. Likewise, high counts of the bacteria Treponema have been linked to maladies like Crohn’s disease and irritable bowel syndrome. Neither of these diseases exist among the Hadza, but their guts contain abundant Treponema.

As someone who has consciously and intentionally altered my gut so it would work closer to normal, to me, this suggests a lot of questions that I do not see being asked.

1) Perhaps modern diets are the problem and the biochemistry they foster rather than microbes per se. How can that be tested?

2) What actually causes "disease"? This implies to me that germs per se are not really the explanation.

3) I would be interested in seeing some data on biochemistry and cell structure of this group as compared to people with modern/Western diets.

4) I would be interested in seeing information related to genetics and how that impacts how their bodies deal with gut flora, etc.

1) The way to test a causal hypothesis is always, at bottom, to do a controlled experiment.[1] So we will tease out the effects of diet on different people by finding experimental volunteers, after institutional review boards approve the experiments, and subjecting the volunteers to controlled diets. This is very difficult to do, as almost all human beings eat when they feel like eating WHAT they feel like eating. Earlier human experiments on effects of diet have actually required the experiment subjects to live in the laboratory long-term, and to have every gram of everything they ate during the experiment measured exactly. Even at that, those experiments came up with few clear conclusions, perhaps because the experiments weren't lengthy enough or didn't include enough subjects for strong inferences.

2) Lots of different things cause lots of different diseases. Both poor diets and infections by microbes can cause some kinds of disease, each independently of the other. It is a fallacy of human thinking to think that there is only one true cause of disease.[2]

3) Yes, it would indeed be interesting to gather more data about biomarkers and tissues of people from more human groups, and especially so after experimental interventions as mentioned in my reply to your first question. It will take very detailed data-gathering to figure out what is going on at the causal level that makes the gut biomes different, and what the different gut biomes do.

4) Your "gut reaction" is correct that this study does not have what human geneticist Robert Plomin would call a "genetically sensitive design," such as what a study of twins[3] would have. The human behavior geneticists with whom I participate in a journal club during the school year have made me very sensitive to how much information is missed if studies of human subjects don't take into account genetic similarity and dissimilarity of the study subjects. Much more work needs to be done on this.

My comment to a friend on Facebook after I posted this same story and friends started talking about it was "One tricky thing for you and me doing 'research' on this is distinguishing short-term effects from long-term effects. My life expectancy here in the United States is already a lot longer than that of most people in the world." It may be that you and I, with the health problems we have today in the United States, are still much better off sticking with our current diets rather than emulating the diets of hunter-gatherers in Africa.

[1] http://escholarship.org/uc/item/6hb3k0nz

[2] http://www.sciencebasedmedicine.org/the-one-true-cause-of-al...

[3] http://www.hup.harvard.edu/catalog.php?isbn=9780674055469