This is a good article: https://news.ycombinator.com/item?id=15253127

This is a fascinating article in terms of the effect of CO2 on plants... but I have a tremendously hard time believing it's affected diets in the first world.

The level of carbs and nutrients in your diet would seem to determined by your dietary choices by an overwhelmingly larger degree. Are you eating french fries or kale?

Does it really matter if my zucchini is slightly less nutritious when I could just eat broccoli rabe instead? Or that my green beans have a trace of carbs when I'm eating a potato on the side? In supermarkets today we've never had greater choice or variety, especially in winter, at least if you're willing to pay for it -- but even in terms of paying for it, food today is the cheapest it's ever been.

I'd be interested in knowing how much the decrease in food nutrients can be offset by taking supplements.

Per the article, increasing CO2 levels in the atmosphere are causing plants to produce more sugars in favor of the (micro)nutrients they'd otherwise have, causing a relative drop in those nutrients. Okay. That makes sense. However, plants being living organisms, they can be rather complex things, and the change in CO2 concentration is not the only changed input to our food supply. There's has been selective breeding and other bio-engineering to select for traits like hardiness to pests, crop yield, appearance, etcetera. There's been changes to how crops are fertilized and harvested. I don't think it's unreasonable to think that any one of these could have interacted with the CO2 concentrations or any other factor to play with nutrient levels, or could be completely overshadowing CO2's effects.

I think this research is a good first step. What I think would be good to study next is to try to find how the CO2 levels can interact with other factors like the ones I listed above, as well as other ones agriculture researchers likely know about that I don't. Perhaps nothing will come of it. Perhaps something cool would come of it. Wouldn't it be awesome if researchers discovered a way to bioengineer food plants, such that by pulling extra CO2 out of the atmosphere, they grow in an extra-nutritious manner?

To the all people who are dismissing the important of the issues being presented in this article, I'd like to invite you to reconsider. I'm reading two main critiques here:

First, that breeding is more important than CO2. That's easy to address as it was discussed in the article. Researchers compared a weed that has had no human cultivation and also compared the genetics of samples from the 1850s, only to find that their protein concentration has declined by 33% since the industrial revolution. Additionally, the main scientist in the article published a meta study that had enough data to account for noise and it isolated CO2 as having an impact on our nutritional density.

Second, another prominent critique I'm reading here is that the conclusions are not important because other factors have so much more importance. I think this criticism is misguided and it's treating the problem as if this were big O or something. Like, "sure, this may be happening but then people could just eat spinach instead of broccoli, problem solved." There's so much that's wrong with this I don't even know where to start, actually.

TL;DR; increased amount of CO2 in the atmosphere reduces amount of nutrients in most plants.

"... calcium, potassium, zinc and iron ... drop by 8 percent ..."

This article seems like much Ado about nothing. My guess is that human selective breeding of plants has far more impact than the effect the article discusses.