Eating as dialogue, food as technology
Food is being reconceived as a currency of communication
abstract / full text
BY HANNAH LANDECKER
Eating is paradoxically completely normal and pretty weird at the same time, once you start to think about it. We eat other beings constantly, in order to remain ourselves. In modern Western logic, the potential oddity of this situation has been dealt with for the most part by assuming that the things we eat stop being themselves after ingestion, that they become fuel or building blocks for us.
However, deep in the detailed pages of journals such as Cell Host & Microbe and Nature Reviews Endocrinology, a profound transformation is occurring in scientific ideas about food and eating that promises to undo assumptions about the relationships between eaters and what is eaten. This transformation, which we might characterize as a shift from a “machinic” to a rather hallucinogenic model of food and its incorporation, endows foodstuffs with much more agency and potency than they ever had in the standard “fuel + building blocks” model, where they were just burned and redeployed.
Rather than mere nosh, provender or raw material, food and its components are now being investigated for communicative and informational properties and for roles in gene regulation, environment sensing, maintaining physiological boundaries and adjusting cellular metabolic programs. Food speaks, cues and signals. Bodies sense and respond in complicated processes of inner conversation only dimly intuited by conscious thought.
Eating as interlocution is a conceptual development that carries with it potentially disorienting new representations of human interiority and autonomy. It is at the same time an immensely practical development, with implications for nutrition and metabolism as sites of potential technological interventions in health and longevity
Thus, we treat food as being without agency, as something that can be acted upon — controlled, produced, cooked, manipulated — but not something that acts in its own right with anything like its own intentionality. Even the famous saying, “you are what you eat,” originated in the chemical imagination of the 19th century: being short of a nutrient such as phosphate was seen to undermine one’s capacity for critical thinking, because the brain was rich in phosphate. The power of substrates lay only in their role as a limiting ingredient for the body.
Of course, dominant discourses always have their alternative undersides, from fresh milk advocacy to macrobiotic diets, but even the form of these minority protests — food is alive! — reveals the dominant logic of food as a blank slate only animated by its eater. Psychedelic mushrooms and this week’s trendy superfood aside, food is almost always the object, not the subject. Humans eat food. Food does not consume humans.
Hundred-year-old ideas about food, eating and health are beginning to change. From the burgeoning science of the human microbiome to a sophisticated understanding of the human intestinal tract as a dense site of information exchange and sensory complexity, researchers are beginning to understand the complex conversation among foodstuffs, microbes and human cells and organs. Some scientists are beginning to ask if key actors in metabolic pathways might be targeted to control aging processes.
Others are watching interchanges happening between food and body cells and asking if biotechnology can mimic the body’s molecular techniques to ferry drugs across membranes. Researchers are testing components of food, and the biochemical products that our metabolisms generate from food, as signals that could potentially be harnessed to tweak cellular energy use or tissue repair.
This presents us with a novel set of answers for the question: What is food? When we eat plants, animals and fungi, we are eating more than calories or carbohydrates, proteins, fats and vitamins. All organisms have their own cells and their own genomes. Therefore, we are eating DNA and RNA all the time. It has long been assumed that these materials are completely broken down and used as building blocks for the eater’s needs.
While this is certainly the case for most consumed molecules, there are other stories unfolding at the microscopic scale of cellular interaction in the intestinal tract. Most foodstuffs — fruit and milk, for example — contain tiny extracellular vesicles, some of which are called exosomes, made originally in the cells of, say, a grapefruit or cow. These nano-sized, fat-wrapped envelopes are particularly good at exiting and entering cells because they can cross lipid membranes and deliver their contents to the other side.
The vesicles’ lipid envelopes are also protective of the transported contents through the potentially harsh territory between cells, such as in the intestinal tract. And the envelope itself can carry information about the target, a kind of address in the form of proteins on the surface that can help gain entry into certain kinds of cells but not others.
“Humans shape their own food worlds — but more attention must be given to how those food worlds shape humans.”
This might seem head-spinning, and indeed the molecular biology behind demonstrating this set of relationships between plants, the gut microbiome and the animal host is amazingly sophisticated. No doubt there is much more to find out as this research is continued. But we can translate its implications fairly bluntly: some genetic material that is ingested is not just broken down for parts. It participates in the work of turning on and off genes in gut bacteria, whose products are relevant to the physiology of the body that eats ginger and hosts a microbiome.
There is a complex interaction, mediated by molecules that we have come to understand as carrying information among the ingested food, the microbiome and the eating body itself. Such findings are of great practical interest because gut integrity is fundamental to digestive and immune health. Having a so-called “leaky gut” allows things into the tissues that can be inflammatory or allergenic. Although the direction of the causal arrows is a little uncertain, the breakdown of the integrity of the gut wall could be both a sign and a probable promoter of autoimmune disorders and chronic inflammation.
As with internal bodily barriers of all kinds — the blood-brain barrier or the placental barrier between mother and child — the ability to keep things out and yet actively and selectively transport needed substances across is fundamental to health. Quite profound philosophical issues also arise from these findings. As with much of the new research around the human microbiome, this story raises an intriguing paradox. We need to eat other entities from outside the body in order to maintain a healthy boundary around the body.
Having a detailed map of the intensive way in which apparently independent entities engage one another — through macrovesicles with tiny RNA cargo — adds another level of appreciation for what these forms of living together entail. As the recent focus on food chains as sources of novel viruses crossing from animals into humans make abundantly clear, humans shape their own food worlds — but more attention must be given to how those food worlds shape humans.
Most people are used to thinking about their senses as residing at the surface of the body — eyes, ears, skin, tongue. Yet it is becoming clear that the viscera are shot through with sophisticated sensory abilities as well. Cued by what we eat, what our microbes further digest and signals from microbes, enteroendocrine cells make over 20 different hormones, most of which possess inscrutable names such as cholecystokinin, glucagon-like peptide-1.
These hormones in turn act as signals to nearby cells, nerves, distant tissue and organs — and to the brain, describing what is happening in the gut and what to do about it.
Enteroendocrine hormones that most people have never heard of drive bodily sensations that everyone is familiar with. From hunger, satiety, sleepiness and nausea to more dimly felt states such as stomach acidity or intestinal motility, the drivers and responses shaping ingestion arise within an ongoing, complex chatter of sensing, signaling and calibrating.
How do enteroendocrine cells “know” and “report” the contents of the alimentary tract? They are specially equipped with receptors that are exquisitely sensitive and highly specific. Receptors are three-dimensional protein structures with high specificity for particular ligands — substances that fit into these receptors and no others, like a key into a lock, unleashing a suite of knock-on effects such as hormone production. Thus, receptors on enteroendocrine cells are “tasting” the substances descending past them and in response, are generating hormones with which to forward that information.
If our food is telling us something, what is it? Some of this conversation is about content or volume, but there may be even more interesting functions to the body’s constant interpretation of the chemistry of its food. Some plant metabolites, for example, are only produced when the plant experiences environmental stressors, like water shortage. If eaten, these plant metabolites can act as signals to cells to favor some metabolic pathways over others.
Is it possible that we have evolved to sense the larger state of the environment through the biology of the organisms we eat and to tune our metabolisms accordingly? On the practical front, is it possible to harness these signals to intentionally foster pathways conducive to metabolic health and longevity? As an aging population faces an unprecedented amount of metabolic disorder, these are pressing questions for individuals and societies.
Gaining a new respect for foods and metabolic processes does not mean rushing out to buy the latest probiotic celery juice or deciding to go on a keto diet. Well over a hundred years of pushing food down the status hierarchy, and demoting the viscera while elevating the brain, means that the kind of science described above is only the beginning of a revolution in resetting the relationships between food and health.
“It is time to recognize the biological potency and agency of food as a metabolic partner rather than a dumb substrate.”
These new worlds — food-body crosstalk and metabolism as a domain of signals and sensing — present many conceptual and technical opportunities. Under the new model of eating as interlocution, food is being reconceived as a currency of communication between the different cells — bacterial and human — that make up the body of the eater.
This chemical chatter between food, microbes, intestines, brains and nerves constitutes a different picture of what it is to know what you are eating. It also raises the question of who is involved in the conversation, since, whether we like it or not, these exquisitely complicated evolutionarily honed systems of cross-kingdom communication are now embedded in the industrialized food worlds.
It is time to recognize the biological potency and agency of food as a metabolic partner rather than a dumb substrate. It is time to push further into the still unclear but vital relationships between metabolism, aging, sleep and immunity. In doing so, we will expand our understanding of what it means to feed humanity.
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