For a number of years now Leach, who lives in Texas and is associated with Kings College in London, has as director of the Human Food Project been looking at the makeup of microbiomes among the Hadza tribe in Tanzania. Leach, who spoke with NutraIngredients-USA at the recent IPA World Congress + Probiota Americas event in San Francisco, said it was the diagnosis of his daughter with Type I diabetes that led him down the path of looking at what some of the gut microbial roots of her condition might be.
Go back to the source
“That led me to hunter gather groups in Africa because everybody in the States and Western Europe wanted to understand the microbiomes of western populations. But if we really want to get at the core the microbiome that we may want to have, we have to study populations that are least impacted by the western world,” Leach said.
Mounting research suggests that westerners harbor a less diverse distal gut microbiota than rural and hunter-gatherer populations. Leach’s ongoing research among the hunter-gatherers in Tanzania suggest that while modern diet and lifestyle choices in the industrialized world are ratcheting down microbial diversity among these populations, it’s the destruction of regional (microbial) species pool that may be playing a bigger role in human health than previously expected.
Leach found that the microbiomes of the Hadza people exhibit a different species profile than do their Western counterparts and are more diverse, which is not surprising considering their different and more varied food sources. Leach found, for example, that the Hadza eat five or more times as much crude fiber as is common in the West. What did come as something of a surprise was how quickly the Hadza guts returned to their base condition after being perturbed, and how likely they were to remain that way even when living a more Westernized lifestyle, as when attending a school in town.
Microbes from the environment
Leach hypothesizes that the vast number of different microbes these people come into contact with daily help to continually inoculate them with donor cells that replenish and fortify their gut microbiomes. While it is too early to draw sweeping conclusions, for Leach the picture is starting to look something like the hygiene hypothesis writ large. Western guts are less diverse and less resilient than those of the Hadza because they are like a forest with too few seeds from too few species blowing in. The Hadza live in intimate contact with their environment, and are in effect coated with it, while we in the West shower frequently, scrub our hands assiduously, live in disinfected houses, eat food prepared in carefully sanitized facilities, travel in cars and work in offices.
The sanitary practices that have been adopted in the West over the past 80 to 100 years all have good reasons behind them. Leach said that the Hadza do not live in some Garden of Eden. Infant mortality is high, for example. But Leach did say he wonders if some tipping point has been crossed, and if sanitary practices may have been taken too far, helping to contribute to the underlying inflammation states now so common in the West. In this view, probiotic supplementation within a sparse microbial background environment can only accomplish so much, akin to planting a bush or two in a forest that is suffering from wide scale trophic collapses.