Mostly because humans evolved to eat processed food. Cooking is an ancient art, from notably before our current species; food is often heavily processed to make it edible (don’t skip over what it takes to eat the fruit of the olive); and local populations do adapt to available food supply.
There’s a taxonomy now for levels of processing (NOVA groups); most research only finds problems with the highest level of processing (NOVA 4), which includes processing methods you can’t do in an ordinary kitchen, or that were not possible ~100 years ago (extrusion, moulding, preprocessing by frying are some examples given).
Do you happen to have any recommended pointers for research on health impacts of processed food? It’s pretty easy to turn up a few recent meta reviews, which seems like a decent place to start, but I’d be interested if there were any other sources, particularly influential individual experiments, etc. (It seems like there’s a whole lot of observational studies, but many fewer RCTs, for reasons that I guess are pretty understandable.) It seems like some important work here might never use the word “processing”.
UPP is terribly written and I imagine mostly useful for its bibliography (I skimmed it in an hour or so). Metabolical is better (although far too difficult a read to be a successful popsci book), although it isn’t specifically focused on processing techniques (it in particular discusses stripping out fibre, adding sugars, reducing water, as some major processing techniques with big issues). You might find something helpful looking in the refs section of either book.
Also as a brief pointer at another cool thing in Metabolical, Lustig claims that exercise is useful for weight loss mostly because of its beneficial impact on cell repair/metabolic system repair (something specific about mitochondria?) and not for the calorie deficit it may or may not create.
I consider Lustig’s science to be quite thorough, I like him a lot. The main point against him is that he personally doesn’t look very metabolically healthy, which I would expect of someone who had spent his life investigating and theorising about what influences metabolic health.
Thanks for the reference! I’m definitely confused about the inclusion of “pre-prepared (packaged) meat, fish and vegetables” on the last list, though. Does cooking meat or vegetables before freezing it (rather than after? I presume most people aren’t eating meat raw) actually change its processed status significantly?
I suspect the word ‘pre-prepared’ is doing a lot of the heavy lifting here—when I see that item on the list I think things like pre-fried chicken, frozen burger patties, veggie pakora, veggies in a sauce for a stir-fry, stuff like that (like you’d find in a ready-made frozen meal). Not like, frozen peas.
Yeah, it’d be helpful to know what heavy lifting is going on there, because I feel like there’s a pretty strong distinction between ‘frozen burger patties that are otherwise indistinguishable from unfrozen burger patties’ and ‘TV dinner’.
A cooked food could technically be called a processed food but I don’t think that adds much meaningful confusion. I would say the same about soaking something in water.
Olives can be made edible by soaking them in water. If they’re made edible by soaking in a salty brine (an isolated component that can be found in whole foods in more suitable quantities) then they’re generally less healthy.
Local populations might adapt by finding things that can be heavily processed into edible foods which can allow them to survive, but these foods aren’t necessarily ones which would be considered healthy in a wider context.
Aside from the rare naturally edible-when-ripe cultivar, olives are (mostly) made edible by fermenting and curing them. With salt, yes. And lye, often. Even olives fermented in water are then cured in brine. What saltless olives are you interacting with?
Edit: Also, cooking is very much processing food. It has all the mechanisms to change things and generate relevant pollutants. It changes substances drastically, and different substances differently drastically. Cooking with fire will create smoke, etc. Cooking with overheated teflon cookware will kill your birds. Mechanisms are important.
And, yes, soaking food in water, particularly for the specific purpose of cultivating micro-organisms to destroy the bad stuff in the food and generate good stuff instead, is some intense, microscopic-level processing.
I had just searched on google about ways to make olives edible and got some mixed results. The point I was trying to make was that the way that olives are typically processed to make them edible results in a product that isn’t particularly healthy at least relatively speaking, due to having isolated chemical(s) added to it in its processing.
The main thing I’m trying to say is that eating an isolated component of something we’re best adapted to eat, and/or adding isolated/refined components to that food, will generally make that food less healthy than it would be were we eating all of the components of the food rather than isolated parts.
I think that process, and more complex variations of that process, are essentially what’s being referred to when referring to the process behind processed foods. I think it’s a generally reasonable term with a solid basis.
Hmm, while I don’t think olives in general are unhealthy in the slightest (you can overload on salt if you focus on them too much because they are brined, but that’s reasonable to expect), there is definitely a meaningful distinction between the two types of processing we’re referencing. Nixtamalization isn’t isolating a part of something, it’s rendering nutrients already in the corn more available. Fermenting olives isn’t isolating anything, (though extracting olive oil is), it’s removing substances that make the olive inedible. Same for removing tannins from acorns. Cooking is in main part rendering substances more digestible.
We often combine foods to make nutrients more accessible, like adding oil to greens with fat-soluble vitamins. I do think there’s a useful intuition that leaving out part of an edible food is less advantageous than just eating the whole thing, because we definitely do want to get sufficient nutrients, and if we’re being sated without enough of the ones we can’t generate we’ll have problems.
This intuition doesn’t happen to capture my specific known difficulty with an industrially processed additive, though, which is a mild allergy to a contaminant on a particular preservative that’s commonly industrially produced via a specific strain of mold. (Being citric acid, there’s no plausible mechanism by which I could be allergic to the substance itself, especially considering I have no issues whatsoever with citrus fruits.) In this case there’s rarely a ‘whole food’ to replace—it’s just a preservative.
I would consider adding salt to something to be making that thing less healthy. If adding salt is essential to making something edible, I think it would be healthier to opt for something that doesn’t require added salt. That’s speaking generally though, someone might not be getting enough sodium, but typically there is adequate sodium in a diet of whole foods.
We often combine foods to make nutrients more accessible, like adding oil to greens with fat-soluble vitamins.
I would disagree that adding refined oil to greens would be healthy overall.
Not sure how much oil we’re talking, but a tablespoon of oil has more calories than an entire pound of greens. Even if the oil increases the availability of vitamins, I am very sceptical that it would be healthier than greens or other whole plants with an equivalent caloric content to the added oil. I believe it’s also the case that fats from whole foods can offer similar bioavailability effects.
At the same time, as far as I’m aware some kinds of vinegar might sometimes be a healthy addition to a meal, despite it’s processing being undoubtedly contrary to the general guidelines I’m defending, so even if I don’t agree about the oil I think the point still stands.
I do think you’re offering some valid points that confound my idea of simple guidelines somewhat, but I still don’t think they’re very significant exceptions to my main point.
I would consider adding salt to something to be making that thing less healthy. If adding salt is essential to making something edible, I think it would be healthier to opt for something that doesn’t require added salt. That’s speaking generally though, someone might not be getting enough sodium, but typically there is adequate sodium in a diet of whole foods.
I’d say it’s too strong a claim that adding salt makes things less healthy. Remember that humans, eating generally mostly plants but some meat as well, developed rather strong craving for sodium salt, just like most herbivorous mammals. If you eat enough meat (not boiled) you don’t need more sodium, if you eat a little meat or a lot but boiled, it’s probably better to add some. If you eat only potatoes, you’ll die without added salt (just kidding, who eats only potatoes).
If you only eat potatoes you wouldn’t die from lack of sodium, the average person would probably become healthier only eating potatoes, it’s been done, though I’m not endorsing that. Potatoes and water already have sodium in them, maybe not quite at the ideal ratio per average calorie but it’s pretty close or maybe in that range depending on the person.
We certainly need some sodium/salt but I think the extent to which most people crave salt is a result of miscalibration due to overexposure and adaptations which aren’t aligned with our current environment.
I minimize added sodium and I don’t really have any cravings for salt anymore, unless you count the cravings I have generally for the food/nutrition I need to sustain myself, which contains roughly enough sodium naturally.
If someone is eating a varied diet of whole foods with no added salt it’s possible that adding a very marginal amount of extra salt would be healthier in some cases, but that’s very far from what is typical.
But then why do medicine portals advise us to be wary of risks associated with too low sodium? It’s claimed to cause insulin resistance, a higher risk of heart disease, hyponatremia, and whatnot. People with any-cause hyponatremia can cure their symptoms with more salt. These people here[1] claim that it’s probably not good for healthy people to artificially (i.e. against their natural desire) restrict their sodium. After reading these claims, what’s the main good side of reducing sodium intake to pretty low?
Generally the hypothesis is that most people will get more sodium in their diet than they crave with their natural desire, if they just eat the food of least resistance (cheapest or easiest, most shelf stable, whatnot). A lot of the sodium that gets into your diet is not so richly activating your taste buds as table salt applied to taste.
What we want overall with salinity is to preserve it at a level that’s correct for us, because we take it in through our diet and excrete it through various processes like sweat. Excessive salt consumption doesn’t directly affect your overall salt and water balance that much, because the body has hormonal regulation of various mechanisms to keep it stable—it’s presumably the overworking of these mechanisms that causes health issues, which is much preferable than it causing issues directly if you’ve seen the effects of the wrong salinity on cells in a petri dish under a microscope.
(The effects on whatever cells I was looking at, which started at a neutral salinity: Raising the salinity (saltier) caused them to shrivel up and dessicate like raisins; lowering the salinity (less salty) caused them to explode.)
It’s my understanding that the controversy is mostly manufactured by industries with large financial interests in selling foods with added sodium. They pay for misleading/inaccurate studies to be done in order to introduce uncertainty and doubt. Whereas it’s my understanding there is a near consensus towards low sodium amongst scientists without direct/indirect industry ties.
I do think there are probably some cases where increasing salt beyond natural levels can be the healthier thing to do given specific health concerns.
We’re talking about a tablespoon of (olive, traditionally) oil and vinegar mixed for a serving of simple sharp vinaigrette salad dressing, yeah. From a flavor perspective, generally it’s hard for the vinegar to stick to the leaves without the oil.
If you aren’t comfortable with adding a refined oil, adding unrefined fats like nuts and seeds, eggs or meat, should have some similar benefits in making the vitamins more nutritionally available, and also have the benefit of the nutrients of the nuts, seeds, eggs or meat, yes. Often these are added to salad anyway.
You probably don’t want to add additional greens with the caloric content of oil to a salad; the difference in caloric density means that 1 tablespoon of oil translates to 2 pounds of lettuce (more than 2 heads), and you’re already eating probably as many greens as you can stomach!
Edit: I should also acknowledge that less processed (cold pressed, extra virgin, and so forth) olive oil has had fewer nutrients destroyed; and may be the best choice for salad dressing. But we do need to be careful about thinking processing only destroys nutrients—cooking, again for example, often destroys some nutrients and opens others up to accessibility.
I typically consume my greens with ground flax seeds in a smoothie.
I feel very confident that adding refined oil to vegetables shouldn’t be considered healthy, in the sense that the opportunity cost of 1 Tablespoon of olive oil is 120 calories, which is over a pound of spinach for example. Certainly it’s difficult to eat that much spinach and it’s probably unwise, but I just say that to illustrate that you can get a lot more nutrition from 120 calories than the oil will be adding, even if it makes the greens more bioavailable.
That said “healthy” is a complicated concept. If adding some oil to greens helps something eat greens they otherwise wouldn’t eat for example, that’s great.
Raw spinach in particular also has high levels of oxalic acid, which can interfere with the absorption of other nutrients, and cause kidney stones when binding with calcium. Processing it by cooking can reduce its concentration and impact significantly without reducing other nutrients in the spinach as much.
Grinding and blending foods is itself processing. I don’t know what impact it has on nutrition, but mechanically speaking, you can imagine digestion proceeding differently depending on how much of it has already been done.
You do need a certain amount of macronutrients each day, and some from fat. You also don’t necessarily want to overindulge on every micronutrient. If we’re putting a number of olives in our salad equivalent to the amount of olive oil we’d otherwise use, we’ll say 100 4g olives, that we’ve lowered the sodium from by some means to keep that reasonable … that’s 72% of recommended daily value of our iron and 32% of our calcium. We just mentioned that spinach + calcium can be a problem; and the pound of spinach itself contains 67% of iron and 45% of our calcium.
… That’s also 460 calories worth of olives. I’m not sure if we’ve balanced our salad optimally here. Admittedly, if I’m throwing this many olives in with this much spinach in the first place, I’m probably going to cook the spinach, throw in some pesto and grains or grain products, and then I’ve just added more olive oil back in again … ;)
And yeah, greens with oil might taste better or be easier to eat than greens just with fatty additions like nuts, seeds, meat, or eggs.
An example where a lack of processing has caused visible nutritional issues is nixtamalization; adopting maize as a staple without also processing it causes clear nutritional deficiencies.
Mostly because humans evolved to eat processed food. Cooking is an ancient art, from notably before our current species; food is often heavily processed to make it edible (don’t skip over what it takes to eat the fruit of the olive); and local populations do adapt to available food supply.
There’s a taxonomy now for levels of processing (NOVA groups); most research only finds problems with the highest level of processing (NOVA 4), which includes processing methods you can’t do in an ordinary kitchen, or that were not possible ~100 years ago (extrusion, moulding, preprocessing by frying are some examples given).
https://ecuphysicians.ecu.edu/wp-content/pv-uploads/sites/78/2021/07/NOVA-Classification-Reference-Sheet.pdf
Do you happen to have any recommended pointers for research on health impacts of processed food? It’s pretty easy to turn up a few recent meta reviews, which seems like a decent place to start, but I’d be interested if there were any other sources, particularly influential individual experiments, etc. (It seems like there’s a whole lot of observational studies, but many fewer RCTs, for reasons that I guess are pretty understandable.) It seems like some important work here might never use the word “processing”.
I don’t remember individual studies but two books that might be helpful:
Ultra-Processed People by Chris van Tulleken
Metabolical by Robert Lustig
UPP is terribly written and I imagine mostly useful for its bibliography (I skimmed it in an hour or so). Metabolical is better (although far too difficult a read to be a successful popsci book), although it isn’t specifically focused on processing techniques (it in particular discusses stripping out fibre, adding sugars, reducing water, as some major processing techniques with big issues). You might find something helpful looking in the refs section of either book.
Also as a brief pointer at another cool thing in Metabolical, Lustig claims that exercise is useful for weight loss mostly because of its beneficial impact on cell repair/metabolic system repair (something specific about mitochondria?) and not for the calorie deficit it may or may not create.
I consider Lustig’s science to be quite thorough, I like him a lot. The main point against him is that he personally doesn’t look very metabolically healthy, which I would expect of someone who had spent his life investigating and theorising about what influences metabolic health.
Thanks for the reference! I’m definitely confused about the inclusion of “pre-prepared (packaged) meat, fish and vegetables” on the last list, though. Does cooking meat or vegetables before freezing it (rather than after? I presume most people aren’t eating meat raw) actually change its processed status significantly?
I suspect the word ‘pre-prepared’ is doing a lot of the heavy lifting here—when I see that item on the list I think things like pre-fried chicken, frozen burger patties, veggie pakora, veggies in a sauce for a stir-fry, stuff like that (like you’d find in a ready-made frozen meal). Not like, frozen peas.
Yeah, it’d be helpful to know what heavy lifting is going on there, because I feel like there’s a pretty strong distinction between ‘frozen burger patties that are otherwise indistinguishable from unfrozen burger patties’ and ‘TV dinner’.
A cooked food could technically be called a processed food but I don’t think that adds much meaningful confusion. I would say the same about soaking something in water.
Olives can be made edible by soaking them in water. If they’re made edible by soaking in a salty brine (an isolated component that can be found in whole foods in more suitable quantities) then they’re generally less healthy.
Local populations might adapt by finding things that can be heavily processed into edible foods which can allow them to survive, but these foods aren’t necessarily ones which would be considered healthy in a wider context.
Aside from the rare naturally edible-when-ripe cultivar, olives are (mostly) made edible by fermenting and curing them. With salt, yes. And lye, often. Even olives fermented in water are then cured in brine. What saltless olives are you interacting with?
Edit: Also, cooking is very much processing food. It has all the mechanisms to change things and generate relevant pollutants. It changes substances drastically, and different substances differently drastically. Cooking with fire will create smoke, etc. Cooking with overheated teflon cookware will kill your birds. Mechanisms are important.
And, yes, soaking food in water, particularly for the specific purpose of cultivating micro-organisms to destroy the bad stuff in the food and generate good stuff instead, is some intense, microscopic-level processing.
I had just searched on google about ways to make olives edible and got some mixed results. The point I was trying to make was that the way that olives are typically processed to make them edible results in a product that isn’t particularly healthy at least relatively speaking, due to having isolated chemical(s) added to it in its processing.
The main thing I’m trying to say is that eating an isolated component of something we’re best adapted to eat, and/or adding isolated/refined components to that food, will generally make that food less healthy than it would be were we eating all of the components of the food rather than isolated parts.
I think that process, and more complex variations of that process, are essentially what’s being referred to when referring to the process behind processed foods. I think it’s a generally reasonable term with a solid basis.
Hmm, while I don’t think olives in general are unhealthy in the slightest (you can overload on salt if you focus on them too much because they are brined, but that’s reasonable to expect), there is definitely a meaningful distinction between the two types of processing we’re referencing. Nixtamalization isn’t isolating a part of something, it’s rendering nutrients already in the corn more available. Fermenting olives isn’t isolating anything, (though extracting olive oil is), it’s removing substances that make the olive inedible. Same for removing tannins from acorns. Cooking is in main part rendering substances more digestible.
We often combine foods to make nutrients more accessible, like adding oil to greens with fat-soluble vitamins. I do think there’s a useful intuition that leaving out part of an edible food is less advantageous than just eating the whole thing, because we definitely do want to get sufficient nutrients, and if we’re being sated without enough of the ones we can’t generate we’ll have problems.
This intuition doesn’t happen to capture my specific known difficulty with an industrially processed additive, though, which is a mild allergy to a contaminant on a particular preservative that’s commonly industrially produced via a specific strain of mold. (Being citric acid, there’s no plausible mechanism by which I could be allergic to the substance itself, especially considering I have no issues whatsoever with citrus fruits.) In this case there’s rarely a ‘whole food’ to replace—it’s just a preservative.
I would consider adding salt to something to be making that thing less healthy. If adding salt is essential to making something edible, I think it would be healthier to opt for something that doesn’t require added salt. That’s speaking generally though, someone might not be getting enough sodium, but typically there is adequate sodium in a diet of whole foods.
I would disagree that adding refined oil to greens would be healthy overall.
Not sure how much oil we’re talking, but a tablespoon of oil has more calories than an entire pound of greens. Even if the oil increases the availability of vitamins, I am very sceptical that it would be healthier than greens or other whole plants with an equivalent caloric content to the added oil. I believe it’s also the case that fats from whole foods can offer similar bioavailability effects.
At the same time, as far as I’m aware some kinds of vinegar might sometimes be a healthy addition to a meal, despite it’s processing being undoubtedly contrary to the general guidelines I’m defending, so even if I don’t agree about the oil I think the point still stands.
I do think you’re offering some valid points that confound my idea of simple guidelines somewhat, but I still don’t think they’re very significant exceptions to my main point.
Appreciate the dialogue:)
I’d say it’s too strong a claim that adding salt makes things less healthy. Remember that humans, eating generally mostly plants but some meat as well, developed rather strong craving for sodium salt, just like most herbivorous mammals. If you eat enough meat (not boiled) you don’t need more sodium, if you eat a little meat or a lot but boiled, it’s probably better to add some. If you eat only potatoes, you’ll die without added salt (just kidding, who eats only potatoes).
If you only eat potatoes you wouldn’t die from lack of sodium, the average person would probably become healthier only eating potatoes, it’s been done, though I’m not endorsing that. Potatoes and water already have sodium in them, maybe not quite at the ideal ratio per average calorie but it’s pretty close or maybe in that range depending on the person.
We certainly need some sodium/salt but I think the extent to which most people crave salt is a result of miscalibration due to overexposure and adaptations which aren’t aligned with our current environment.
I minimize added sodium and I don’t really have any cravings for salt anymore, unless you count the cravings I have generally for the food/nutrition I need to sustain myself, which contains roughly enough sodium naturally.
If someone is eating a varied diet of whole foods with no added salt it’s possible that adding a very marginal amount of extra salt would be healthier in some cases, but that’s very far from what is typical.
But then why do medicine portals advise us to be wary of risks associated with too low sodium? It’s claimed to cause insulin resistance, a higher risk of heart disease, hyponatremia, and whatnot. People with any-cause hyponatremia can cure their symptoms with more salt. These people here[1] claim that it’s probably not good for healthy people to artificially (i.e. against their natural desire) restrict their sodium. After reading these claims, what’s the main good side of reducing sodium intake to pretty low?
https://doi.org/10.1093/qjmed/hcr124
Generally the hypothesis is that most people will get more sodium in their diet than they crave with their natural desire, if they just eat the food of least resistance (cheapest or easiest, most shelf stable, whatnot). A lot of the sodium that gets into your diet is not so richly activating your taste buds as table salt applied to taste.
What we want overall with salinity is to preserve it at a level that’s correct for us, because we take it in through our diet and excrete it through various processes like sweat. Excessive salt consumption doesn’t directly affect your overall salt and water balance that much, because the body has hormonal regulation of various mechanisms to keep it stable—it’s presumably the overworking of these mechanisms that causes health issues, which is much preferable than it causing issues directly if you’ve seen the effects of the wrong salinity on cells in a petri dish under a microscope.
(The effects on whatever cells I was looking at, which started at a neutral salinity: Raising the salinity (saltier) caused them to shrivel up and dessicate like raisins; lowering the salinity (less salty) caused them to explode.)
It’s my understanding that the controversy is mostly manufactured by industries with large financial interests in selling foods with added sodium. They pay for misleading/inaccurate studies to be done in order to introduce uncertainty and doubt. Whereas it’s my understanding there is a near consensus towards low sodium amongst scientists without direct/indirect industry ties.
I do think there are probably some cases where increasing salt beyond natural levels can be the healthier thing to do given specific health concerns.
We’re talking about a tablespoon of (olive, traditionally) oil and vinegar mixed for a serving of simple sharp vinaigrette salad dressing, yeah. From a flavor perspective, generally it’s hard for the vinegar to stick to the leaves without the oil.
If you aren’t comfortable with adding a refined oil, adding unrefined fats like nuts and seeds, eggs or meat, should have some similar benefits in making the vitamins more nutritionally available, and also have the benefit of the nutrients of the nuts, seeds, eggs or meat, yes. Often these are added to salad anyway.
You probably don’t want to add additional greens with the caloric content of oil to a salad; the difference in caloric density means that 1 tablespoon of oil translates to 2 pounds of lettuce (more than 2 heads), and you’re already eating probably as many greens as you can stomach!
Edit: I should also acknowledge that less processed (cold pressed, extra virgin, and so forth) olive oil has had fewer nutrients destroyed; and may be the best choice for salad dressing. But we do need to be careful about thinking processing only destroys nutrients—cooking, again for example, often destroys some nutrients and opens others up to accessibility.
I typically consume my greens with ground flax seeds in a smoothie.
I feel very confident that adding refined oil to vegetables shouldn’t be considered healthy, in the sense that the opportunity cost of 1 Tablespoon of olive oil is 120 calories, which is over a pound of spinach for example. Certainly it’s difficult to eat that much spinach and it’s probably unwise, but I just say that to illustrate that you can get a lot more nutrition from 120 calories than the oil will be adding, even if it makes the greens more bioavailable.
That said “healthy” is a complicated concept. If adding some oil to greens helps something eat greens they otherwise wouldn’t eat for example, that’s great.
Raw spinach in particular also has high levels of oxalic acid, which can interfere with the absorption of other nutrients, and cause kidney stones when binding with calcium. Processing it by cooking can reduce its concentration and impact significantly without reducing other nutrients in the spinach as much.
Grinding and blending foods is itself processing. I don’t know what impact it has on nutrition, but mechanically speaking, you can imagine digestion proceeding differently depending on how much of it has already been done.
You do need a certain amount of macronutrients each day, and some from fat. You also don’t necessarily want to overindulge on every micronutrient. If we’re putting a number of olives in our salad equivalent to the amount of olive oil we’d otherwise use, we’ll say 100 4g olives, that we’ve lowered the sodium from by some means to keep that reasonable … that’s 72% of recommended daily value of our iron and 32% of our calcium. We just mentioned that spinach + calcium can be a problem; and the pound of spinach itself contains 67% of iron and 45% of our calcium.
… That’s also 460 calories worth of olives. I’m not sure if we’ve balanced our salad optimally here. Admittedly, if I’m throwing this many olives in with this much spinach in the first place, I’m probably going to cook the spinach, throw in some pesto and grains or grain products, and then I’ve just added more olive oil back in again … ;)
And yeah, greens with oil might taste better or be easier to eat than greens just with fatty additions like nuts, seeds, meat, or eggs.
An example where a lack of processing has caused visible nutritional issues is nixtamalization; adopting maize as a staple without also processing it causes clear nutritional deficiencies.