Wednesday 22 November 2017

Lessons on the gut flora of the Hadza

If we want to know how we used to live, we should look at the Hadza of Tanzania. They can also teach us a lot about gut flora, but we do have to be fast as the first Hadza people have been spotted using a mobile telephone.


The Hadza – a traditional tribe in Tanzania – are an important source of information about how our ancestors lived. However, nowadays only 200 Hadza people live like their (not so ancient) ancestors. The remainder of the tribe, around 800 hunter-gatherers, are becoming westernised at a rapid pace.


Because it is anticipated that their traditional lifestyle will have disappeared completely within 10 to 20 years, research into their lifestyle is taking place very quickly. The results of this research are published frequently in Science and Nature [1, 2, 3] and is often replicated in mainstream media.


New insights

The latest result is that the diet and the microbiome of the Hadza change according to the seasons [3]. Certain gut bacteria that help with the digestion of, for example, fibres, disappear when the diet is low in fibre. These bacteria return when fibres return. This process has been observed in the past in mice [1].


In that same study in mice, it was also discovered that long-term fibre deficiencies can have a huge impact on the gut flora. When mice had fibre deficiencies for four generations, the specific gut bacteria disappeared permanently. The scientists question whether this has already happened in today’s Westerners, or whether other factors mainly play a role in our depleted gut flora.


Greater diversity in gut flora

It is a fact that our gut flora is depleted in comparison to that of hunter-gatherers living a traditional way of life. Past research shows a much greater diversity in the Hadza when compared to an Italian control group [2]; this was mainly in relation to seasonal bacteria that occur in many African tribes. It is conjectured that this is purely down to the diet.


The study also draws an interesting comparison, between the Paleo diet on the one hand and Mediterranean diet on the other hand.


The Paleo Diet

The Hadza mainly eat meat, honey, baobab fruit, berries and tubers and there is no agriculture. They also obtain less than 5 percent of their calories from agricultural products from the surrounding areas. The seasonal pattern consists of eating meat and vegetables in the dry season and fruit and vegetables in the wet season.


Mediterranean diet                       

In the aforementioned study, Italians mainly lived on commercial agricultural products. Their diet is referred to as ‘Mediterranean’ by the researchers, a lot of vegetables, fresh fruit, pasta, bread and olive oil, but few dairy products, poultry, fish and red meat. More than half of the carbohydrates eaten consisted of easy-to-digest starch and a third consisted of sugar. Soluble and insoluble fibres accounted for just 10 percent of the diet.


Incidentally, the reported diet of the Italians who participated in this study deviates in key points from the norm generally applicable to Mediterranean food. For example, they eat less fish and more sugar. Although there have been proven benefits of a Mediterranean diet, the Paleo diet seems more capable of maintaining a varied microbiome.


Rapid changes

Our gut flora changes from day to day and even from hour to hour, depending on what we have eaten. What would happen if someone from the West were to eat the diet and have the lifestyle of the Hadza people for a while? A study has taken place into this, in a somewhat less formal manner [4].


The positive news from this study is that within just three days, there is an enormous increase in the diversity of the gut flora. The not so good news is that as soon as a conventional Western diet is eaten, this gut flora disappears just as quickly.



The gut flora can be actively influenced and results can be rapid. For example, by eating a Paleo diet, or a modified Mediterranean diet, with more soluble and insoluble fibres instead of mainly bread and pasta. Targeted treatment of the gut can precede this, or this can take place simultaneously, with glutamine, prebiotics and probiotics. The avoidance of antibiotics (where possible) is also an important strategy.


However, the main conclusion is that a change in the diet only improves the gut flora for a sustained period when the pattern becomes a permanent component of the lifestyle; if there is a temporary relapse, the gut flora can be restored with targeted supplementation.


But you don’t become healthy by simply eating a few more fibres every now and then. The microbiome in our intestines depletes immediately when your client falls back into old habits.



[1] Erica D. Sonnenburg, Samuel A. Smits, Mikhail Tikhonov, Steven K. Higginbottom, Ned S. Wingreen & Justin L. Sonnenburg, Diet-induced extinctions in the gut microbiota compound over generations, Nature 529, 212–215 (14 January 2016).

[2] Schnorr, S.L. et al.,Gut microbiome of the Hadza hunter-gatherers, Nature Communications 5, article number 3654 (2014)

[3] Samuel A. Smits, Jeff Leach, Erica D. Sonnenburg, Carlos G. Gonzalez, Joshua S. Lichtman, Gregor Reid, Rob Knight, Alphaxard Manjurano, John Changalucha, Joshua E. Elias, Maria Gloria Dominguez-Bello, Justin L. Sonnenburg. Seasonal cycling in the gut microbiome of the Hadza hunter-gatherers of Tanzania. Science, Vol. 357, Issue 6353, pp. 802-806