If you want to claim that coloring or preservatives are bad, then just make that claim instead of the more vague "processed foods".

The NOVA system covers this.

> Group 1 - Unprocessed or minimally processed foods (fruit, vegetables, eggs, meat, milk, etc.) Group 2 - Foods processed in the kitchen with the aim of extending their shelf life. In practice, these are ingredients to be used in the kitchen such as fats, aromatic herbs, etc. to be kept in jars or in the refrigerator to be able to use them later. Group 3 - Processed foods. These are the foods obtained by combining foods of groups 1 and 2 to obtain the many food products for domestic use (bread, jams, etc.) made up of a few ingredients Group 4 - Ultra-processed foods. They are the ones that use many ingredients including food additives that improve palatability, processed raw materials (hydrogenated fats, modified starches, etc.) and ingredients that are rarely used in home cooking such as soy protein or mechanically separated meat. These foods are mainly of industrial origin and are characterized by a good pleasantness and the fact that they can be stored for a long time.

Nobody really knows for certain what things do to the body even in isolation. For one example, see Yellow #5 [1]. It's associated with all sorts of nasty stuff, but actually proving a causal relationship is not really possible. So some countries ban it, some require special scary labeling for products with it, and in other countries it's A-OK.

And processed foods aren't in isolation. You're mixing up all sorts of stuff which can viably result in chemical and other changes which will vary by product, producer, and even time. Trying to pin all of that down is not really possible.

[1] - https://en.wikipedia.org/wiki/Tartrazine#Potential_health_ef...

It's meant as a rule of thumb. That level of precision is unnecessary.

Generally speaking, industrially-processed foods are going to be overall less healthy than less-processed alternatives. There are a multitude of reasons this may be so, and between them there's enormous variance in both the size of and our confidence in those effects, not to mention between specific products.

Being overly specific just invites pointless quibbling over those details. Of course, not being specific just started this pointless quibble, so damned if you do damned if you don't.

I'm specifically not making that claim. (I also don't disagree with that claim) I'm making the claim that those activities are indicative of a constellation of activities that as a whole are categorically unhealthy.

Because doing that is an invite to the field of weak/conflicting evidence because food science just don't have this level of granularity yet. Though I believe to be undeniably that the replacement of ultra-processed cheap foods with real food is beneficial. I'm too lazy to research it for the sake of an argument but I can support it at least on a personal/anecdotal level. It's not scientific but as a rule of thumb if you don't know how it was made better to not eat it.

Which particular part of this process is unhealthy, though? And how unhealthy is it?

If the problem is the food coloring, then we need to go out and say so. If the problem is the high fat content, we shouldn't pretend that home cooking with lots of oils (which oils?) isn't any healthier than processed food. Is the spoon of sugar I add to my home-made stir-fry sauce the problem, or is it the fact that I am frying it, or the fact that I serve it next to a plate full of rice?

Avoiding processed foods is more about avoiding the unknown than avoiding something specific. I would say more analogous to rolling your own tobacco vs buying a pre-packaged cigarette. At least you know what's in there for the most part.

Can you prove there isn't a teapot floating around saturn?

I don't view there to be a burden of proof that I should eat something unless someone can present data that that specific thing is unhealthy

I can use inference to decide there is a reasonable probability that something is unhealthy without some arbitrary burden of specific proof

Certainly more specificity would be useful and I hope we get there someday. But that doesn't mean we should ignore the imperfect information we have in the meantime.

In this case, the link between processed foods (Nova groups 3 and especially 4) seems strong enough to warrant minimizing them in my diet even though the evidence for the specific ingredients or mechanisms is weaker.

My understanding is that it is the absorption which is the problem.

The example I was given was eating raw sweetcorn. Infamously, you can be sure a certain amount will pass through you undigested.

If you grind it up first and make bread out of the flour you will absorb far more.

Secondly breaking things down robs them of flavour and texture.

To compensate manufacturers add a load of now easily absorbed salt, sugar and fat.

None of that is good depending on what your goals are.