I’ve been meaning to get this one out of the way. As the microbiome and the importance of our gut microflora composition begins to get more attention, it will become, as all things do, subject to preconceived notions and biases about health. And perhaps nothing is as preconceived and biased in the world of diet and health as the idea that intake of meat and its associated saturated fat are inherently unhealthy.
Case in point. A writer for The Guardian reports on having his gut bacteria sequenced and drops a couple of misconceptions that really need to be cleared up:
At the broadest level, the phylum level, my microbiota, in common with everyone else’s, was dominated by two types: firmicutes and bacteroidetes. The western diet, by which we tend to mean the North American diet, is high in fat and protein. In this diet bacteroidetes usually make up more than 55% of the gut microbiota, and sometimes, in North America itself, as much as 80%. In Europe, the average numbers vary from country to country. In my case I had 34%.
Again these were positive results. Lachnospira degrade pectins and ferment dietary fibres and I have three times more than typical. And bacteroides are often associated with meat-based, high-protein, high-fat diets, just as alistipes tend to be more present in people who eat less plant-based food. In sum that meant my gut – the lack of six-pack notwithstanding – was probably in good shape.
But by then he had managed to make a blind prediction of my diet that was uncannily accurate. He saw very little evidence of meat-eating – I haven’t eaten meat for 30 years.
Where to even start? The idea that specific colonic bacteria are enriched by meat and fat consumption is reflective of having missed a third grade lesson on anatomy. Meat and fat are, by and large, absorbed in the small intestine. Non-digestible carbohydrates — fiber — pass into the large intestine to be fermented by bacteria. In the context of diet, the composition of your microflora will be a reflection of the amount and type of fiber ingested.
Tell me how, exactly, one would see “evidence” of high or low meat consumption in this scenario. High meat and fat consumption and high plant consumption are not mutually exclusive. In fact, there is an entire diet devoted to this eating pattern. I forget the name.
To make it even clearer, I’ll once again highlight the evidence that I talked about in this post, showing what plant fiber — and plant fiber alone — can do to your gut microbiome:
Notice what doesn’t change in this experiment? Meat and fat consumption. Because it doesn’t matter. While it’s true that, on a personal level, your decision to eat meat and fat may lead you to eat less plants, that is a personal decision. And this may in fact explain the oft-cited correlation between high meat (red meat, specifically) intake and diseases like heart disease and colorectal cancer. In other words, “high meat & fat” may have really been “low fermentable plant fiber” all along. But again, these are not mutually exclusive eating patterns. Sure, at a certain point, meat and fat intake can begin to “crowd out” plant consumption to a level that is not optimal for gut health. But that is a far cry from saying that meat and fat themselves cause disease. Advice like that could lead one to cut meat and saturated fat out of one’s diet, and instead increase their intake of sugar, processed grains, and industrially-processed oils. Theoretically. Failure to make important, nuanced distinctions could, say, lead us down a 40-year road that results in no improvement in disease prevalence.
Of course, our diet-nutriton-health industrial complex can’t allow for such a nuanced idea. It’s all a one-or-the-other, good vs evil, science-illiterate holy war, isn’t it?
It’s the omnivore’s dilemma.
Update: An exchange in the comments led me to realize a further piece of evidence showing how useless it is to focus on meat & fat: the chart above shows that a high meat + fat + plant fiber diet produces MORE Firmicutes and LESS “meat & fat loving” Bacteroidetes than the author of the Guardian piece reports for himself. He reports 51% Firmicutes and 34% Bacteroidetes. From the chart above, it looks like high meat/fat/fiber produces around 75% Firmicutes, and less than 25% Bacteroidetes. I’m willing to bet that the Actinobacteria (good guys, Bifidobacteria) in that chart are much higher than in our intrepid reporter as well.