Remarkable findings on socioeconomic status and the microbiome
“You are what you eat” is an expression popularized in the 1930s by Chicago weight-loss pioneer Dr. Victor Lindlahr, who hosted a popular radio show about nutrition.
Incidentally, he championed what he called “The Catabolic Diet”, catabolic foods being items your body requires more calories to digest than are contained within the food itself.
An apple, for example, contains around 90 calories, but metabolizing it uses around 180 calories, so in theory eating an apple actually burns off about 90 calories.
Of course, in the 1930s little was known about the human microbiome, but “you are what you eat” certainly holds a substantial amount of truth when it comes to your gut bacteria.
In 2009 researchers based at Washington University School of Medicine in St. Louis, Missouri ran a mind-boggling experiment in which previously germ-free mice were turned into tiny, living models of human gastroenterology after receiving transplants of human fecal matter.
What do you think happened to these rodents’ microbiota when they were switched from a low-fat, high-fiber diet to a high-fat, high-sugar regime typical of many in the West?
You possibly won’t be too surprised to learn that the composition of their bacteria changed, but you may be as astounded as me to learn how swiftly this happened.
It took just a day.
Thinking about the effects of diet on the microbiome got me wondering about how gut flora might vary with socioeconomic status, which in turn led to some fascinating reading.
Around the world, lower socioeconomic status is generally associated with higher mortality, an effect experts say is mainly due to factors such as higher tobacco use, physical inactivity, and poor nutrition.
But does poor nutrition equate to an unhealthy microbiome?
Well, the answer isn’t quite as clear-cut as you might imagine.
Let’s turn first to a 2015 study by scientists at the International Medical University in Kuala Lumpur, Malaysia, who examined three groups of adolescent schoolchildren – one consisting of Malays, another of Chinese, and a third from a tribe called the Orang Asli.
Of these three groups, the Chinese children had the wealthiest parents, while many of the Orang Asli kids’ families lived below the poverty line and were socially marginalized.
One factor that interested the researchers was bacterial diversity: how many species of bacteria were found in the gut?
In general terms, high diversity is healthy, while low diversity can be associated with inflammatory bowel disease, metabolic disorders, and obesity.
So guess whose guts had the highest diversity?
Actually it was the economically deprived Orang Asli children, while the relatively wealthy Chinese kids had the lowest diversity.
The Chinese children had homes that were in general spotless when compared to the places the Orang Asli kids lived in, leading the scientists to conclude that “too much” hygiene could lead to a depleted microbiome.
Fascinating results from a reasonably small number of study participants, fairly typical of scientific research projects.
But let’s now turn to a rather bigger – and pretty awesome – study involving a few more participants.
Yup, the entire population of Denmark.
5.3 million people, to be precise.
Between 1993 and 2004 researchers followed every person in the country, and thanks to a system where bacterial gastrointestinal infections must by law be notified to the authorities, the scientists could track gut disease and then, remarkably, cross-tabulate this with socioeconomic status.
In another counter-intuitive finding, being better-off in Denmark makes you more, not less, likely to suffer from gut infections, particularly Campylobacter, Shigella, and Salmonella.
Research suggests that this may be due to wealthier people eating more “adventurous” food and traveling more widely.
However, lest we conclude from all this that low socioeconomic status is the gateway to a healthy microbiome, let’s be clear that it almost certainly isn’t.
Helicobacter pylori is a distinctly unpleasant bacterium described by Cairo University researchers in 2010 as a “poor man’s gut pathogen”.
H. pylori can play a disturbing role in gastric diseases and cancer.
But at the age of five, less than 5% of U.S. children are infected by it.
By contrast, 50% of under-fives in developing countries are infected, largely because of poor hygiene.
The Cairo University researchers went on to label H. pylori “a chronic colonizer of half the human race”, with serious implications for those in developing countries who could ironically find newly-extended lifespans placing them at high risk of serious gastric conditions, even cancer.
If you’re a regular reader of my Monday emails, you’ll know we generally like to close on a lighter note, but that’s rightly not feasible today.
Serious bacterial infection?
It’s no laughing matter.