There have been changes in food over the last 50 years, and those changes have been driven by the food industry's requirement to make a profit. I may be wrong, and I'm happy to discuss this with people who know more (or less) than me, but I think the most important change has been that calories have gotten cheaper, but other nutrition has gotten more expensive.I wanted to explore what I meant by that.
Now I should make it clear that I have no special qualifications to write about nutrition, quite the lack of it in fact. I'd like to know more about the science of nutrition, what we think we know, what we think we don't know, and how we know what we think we know, but I don't. From what I've read there is pretty universal agreement about what out bodies need to fuel and rebuild themselves (calories, vitamin A, Protein etc.) and reasonable levels of agreement about which foods have which nutrients (with some disagreeements about how much of these nutrients we manage to absorb). There appears to be a huge amount of disagreement about what (if any) negative effects various foods might have* and for this post I'm going to leave that well alone for this post. I'd love it if anyone who knows more about nutrition science and history wanted to post in the comments, but these comments are based on what I know. I also want to say that I'm thinking about changes that have happened in the last 60 years, because nothing pisses me off more than people talking about some vague sort of olden days that never actually existed. I'm talking about the changes that have happened post-World War II.
The basic idea is obvious, most people know what calories are (but often think of them as something to avoid, rather than a measure of energy), and that the other things you need from food are vitamins, minerals, fat, protein and fibre.
The idea that calories has got cheaper has also been relatively widely covered. I'm unsure how much this part of changes in agriculture, and how much is about changes in post harvest food technology, but we can produce calories cheaper than we used to.
Now I want to go on the record and say that I think that cheap calories are a good thing. I believe every person on this planet should have enough food to fuel their body without even thinking about it. It makes me furious when people attack cheap calories as if fuel for our bodies was something that only rich people were entitled to.
To me the problem is that other nutrients have got more expensive. Now I'm not sure if this is true absolutely, it probably depends on which nutrients and where you live. I'd love to see the statistics about average income and price of different sorts of food.
Nutrients can get more expensive while food gets cheaper. Growers that make food for a profit, rather than for nutrients, might prioritise other things besides nutritional value when they select which varieties to grow (or the people who make their seeds might be the people who make the priorities).
It is true that other nutrients have got cheaper relative to calories, and it's even more true if you factor in the time it takes to make the food. One thing that has happened in the last 40 years is that the average number of hours each person works has increased. Mostly that's about increased participation by women in paid employment, it's also about the fact that our labour legislation used to be a lot better than it is now, and so fewer people had more than 1 job.
The market in food that doesn't take much time to prepare has increased. There's no reason that food that is quick to prepare can't have both calories and other nutrients. But when food is made for profit it's easier to make cheap food that is low in nutrients.
The politics of food are incredibly important, but the entire discourse around food is based around fudging the reality of how food is made. The so-called obesity epidemic and the focus on calories ignores what the actual problem is.
* It makes sense to me that possible damaging effects of different foods would be hard to understand for a number of reasons. The first is the individuality of it - some people (say me) can be allergic to dairy products, but it's hard to find someone who doesn't need Protein. The second is the difficulty of studying these sorts of things, since if you base your evidence on studying what people do eat then you run into all sorts of problems around controlling for other factors and cause and effect, and when you try and do it the way they do drug studies then you run into the problem that people won't necessarily eat what you tell them to.