One difficult thing that keeps coming up, in nutrition modeling, is the gut microbiome. People present hypotheses like: soluble fiber is good, because gut bacteria eat it, and then do other good things. Or: fermented foods are good, because they contain bacteria that will displace and diversify the preexisting bacteria, which might be bad. Or, obesity is caused by a bad gut microbiome, so fecal matter transplants might help. But there’s a really unfortunate issue with these theories. The problem with gut microbiome-based explanations, is that the gut microbiome can explain almost anything.
I don’t mean this in the usual pejorative sense, where an overly-vague theory can be twisted by epicycles into fitting any data. I mean it in a more literal sense: different people have different species of microorganisms in their guts, these species can react to things we eat in important ways, these interactions may vary across wide swathes of conceptual space, and we have little to no visibility into which species are present where. There’s nothing keeping them consistent between people, or within one person across long spans of time, or within one person across changes in dietary pattern.
Phrased slightly differently: the main effect of the gut microbiome is to drive interpersonal variation.
I bring this up not because I have something especially insightful to say about gut microbiomes, but because this makes a good lens for a meta-level issue. I’ve been studying nutrition, at varying levels of seriousness, for a long time; now that I’ve accumulated a lot of unusual beliefs, and gotten into a writing groove, I think it’s worth explaining the generator behind my thinking.
The dominant paradigm of nutrition science is to try to make a food-goodness classifiers: define some reference class of foods and say “these ones are good”, and some other reference class of foods and say “these ones are bad”. People want a direct answer to the question of what they should eat, rather than gears-level models with which they might discover what they should eat.
The food-goodness-classifier paradigm cannot, and will not ever, figure out how people should relate to their gut microbiomes. Nor will this paradigm yield insights into how to handle genetic variation, or medical conditions that interact with metabolism like T1DM. I used to think the food-goodness-classifier paradigm would at least contain an answer to obesity, somewhere. Today, I think it’s failed, and will never succeed, at obesity too.
My search space for nutrition insights is: Everything except the food-goodness-classifier paradigm.
And so I find myself with strong opinions about the time dynamics of digestion. A few alternate stories about the environment of evolutionary adaptation, where food is hazardous rather than scarce, or scarce in unusually specific ways. A map of the body’s multiple energy-storage mechanisms, where the central mystery is why there rather than why so much. Beliefs about how, if you found yourself in an alien biome with randomly rewired taste buds, you would figure out a healthy diet from scratch. More methodological objections to major studies than you can shake a stick at.
This does sometimes cash out into food-goodness-classifier opinions, and I did have to get through a lot of those opinions to get there. Sometimes, these are weird reversals of standard advice, with deep models behind them; eg, I am generally pro-salt and pro-fat, for reasons I’ll get into in a later post. Other times I just agree with what everyone else thinks, and don’t really bring it up, because “yo, don’t get scurvy” isn’t insightful, and I’m not trying to be exhaustive in that way.
I’m not trying to create an optimal diet. These posts are not leading up to a meal plan, and if you’re just trying to figure out what to eat, you are not my intended audience. Instead, my goal is to break nutrition science out of its rut, and lay groundwork for progress.
these interactions may vary across wide swathes of conceptual space, and we have little to no visibility into which species are present where.
Through gene sequencing we have the technology to assess which species are present in which people. It’s a nascent scientific field but that doesn’t mean that it doesn’t exist.
One difficult thing that keeps coming up, in nutrition modeling, is the gut microbiome. People present hypotheses like: soluble fiber is good, because gut bacteria eat it, and then do other good things. Or: fermented foods are good, because they contain bacteria that will displace and diversify the preexisting bacteria, which might be bad. Or, obesity is caused by a bad gut microbiome, so fecal matter transplants might help. But there’s a really unfortunate issue with these theories. The problem with gut microbiome-based explanations, is that the gut microbiome can explain almost anything.
I don’t mean this in the usual pejorative sense, where an overly-vague theory can be twisted by epicycles into fitting any data. I mean it in a more literal sense: different people have different species of microorganisms in their guts, these species can react to things we eat in important ways, these interactions may vary across wide swathes of conceptual space, and we have little to no visibility into which species are present where. There’s nothing keeping them consistent between people, or within one person across long spans of time, or within one person across changes in dietary pattern.
Phrased slightly differently: the main effect of the gut microbiome is to drive interpersonal variation.
I bring this up not because I have something especially insightful to say about gut microbiomes, but because this makes a good lens for a meta-level issue. I’ve been studying nutrition, at varying levels of seriousness, for a long time; now that I’ve accumulated a lot of unusual beliefs, and gotten into a writing groove, I think it’s worth explaining the generator behind my thinking.
The dominant paradigm of nutrition science is to try to make a food-goodness classifiers: define some reference class of foods and say “these ones are good”, and some other reference class of foods and say “these ones are bad”. People want a direct answer to the question of what they should eat, rather than gears-level models with which they might discover what they should eat.
The food-goodness-classifier paradigm cannot, and will not ever, figure out how people should relate to their gut microbiomes. Nor will this paradigm yield insights into how to handle genetic variation, or medical conditions that interact with metabolism like T1DM. I used to think the food-goodness-classifier paradigm would at least contain an answer to obesity, somewhere. Today, I think it’s failed, and will never succeed, at obesity too.
My search space for nutrition insights is: Everything except the food-goodness-classifier paradigm.
And so I find myself with strong opinions about the time dynamics of digestion. A few alternate stories about the environment of evolutionary adaptation, where food is hazardous rather than scarce, or scarce in unusually specific ways. A map of the body’s multiple energy-storage mechanisms, where the central mystery is why there rather than why so much. Beliefs about how, if you found yourself in an alien biome with randomly rewired taste buds, you would figure out a healthy diet from scratch. More methodological objections to major studies than you can shake a stick at.
This does sometimes cash out into food-goodness-classifier opinions, and I did have to get through a lot of those opinions to get there. Sometimes, these are weird reversals of standard advice, with deep models behind them; eg, I am generally pro-salt and pro-fat, for reasons I’ll get into in a later post. Other times I just agree with what everyone else thinks, and don’t really bring it up, because “yo, don’t get scurvy” isn’t insightful, and I’m not trying to be exhaustive in that way.
I’m not trying to create an optimal diet. These posts are not leading up to a meal plan, and if you’re just trying to figure out what to eat, you are not my intended audience. Instead, my goal is to break nutrition science out of its rut, and lay groundwork for progress.
(Crossposted with Facebook)
Through gene sequencing we have the technology to assess which species are present in which people. It’s a nascent scientific field but that doesn’t mean that it doesn’t exist.