A lot of people who eat this produce and don't take any supplements are healthy and doing fine. If the nutrient levels have really fallen so much, then, how come malnutrition isn't an epidemic?
* The general population does have a bunch of nutrient deficiencies in their diet - https://www.healthline.com/nutrition/7-common-nutrient-defic... as an introduction to the problem
* The article is making claims about a 100 year timespan and I doubt we have comparable data on nutrient deficiencies which is that old
* Daily calorie intake has probably doubled in that time period, so in theory you'd hope daily intake of all essential nutrients would double as well, but here we are with almost half of women and children having iron deficiency, with widespread deficiency in vitamins D and B12, half of the population not getting the recommended calcium intake etc.
So I think as an example to start throwing some numbers out there. About 40% of Americans don't get the recommended amount of calcium. First chart in the article shows calcium in vegetables at retail declining by 90% in the last century.
I think we have evidence establishing that nutrient deficiency leads to cravings - maybe declining nutrient density is a factor encouraging overeating and obesity?
Pretty interesting topic
Malnutrition isn't as visible as obesity though, you can be a fat fuck and still malnourished in some aspects, but if you're already fighting high blood pressure and diabetes these issues are way down your list of problems. It can be very subtle like micro gut health, teeth health, long term bone health, children not growing as tall as they could, &c.
Virtually no metrics are going in the right direction in the US when it comes to nutrition: https://globalnutritionreport.org/resources/nutrition-profil...
https://www.theguardian.com/lifeandstyle/2015/feb/10/nutriti...
Maybe there are other health effects like people subconsciously eating more because the body is craving certain micronutrients, leading to getting fat from too many macronutrients.
You could create several cohort with different co-controlled fixes for each: more calories, more protein, more fiber, more nutrients.
Then evaluate the percentage of successfully treated patients in each cohort.
It's of course a difficult study, since someone with a bad diet will lack practically everything, so more things will work than not. I'd also be curious to see how you would design a real food diet high in micronutrients without accidentally adding a bunch of fiber in the process
Then in phase 2 we split into a control group that still buys from any store, a second group that only has access to foods with high nutrition content, and a third group that only has access to foods with low nutrition content. The same types of food should be offered just high and low nutrition options (e.g. zuchinnis, brocolli, tomatoes, apples, ...)
We then check if there's any significant effect on caloric intake (given a certain time for them to adjust).