They are also more abundant than they used to be and that's a valid tradeoff to consider. Would it be worth it to only have access to seasonal produce local to your region for that produce testing better? Make do with pickles and potatoes instead of fresh fruit and vegetables in late fall through early spring? If not, shelf life, productivity and greenhouse feasibility are relevant metrics in addition to taste and vitamins. Old ways of gardening are still available, but most people will end up using these as a supplement rather than replacement to supermarket food that is at least always there in sufficient amounts.
If my food isn't nutritious I either wither away or am forced to eat more food, which comes with more calories. So, no: it seems like it is better to make do with seasonal foods than to live in a world where I can technically experience a tomato but... is it really a tomato if it just tastes like a tomato but otherwise confers none of the value of a tomato? (If you are saying the alternative is NO food, then sure; but I think the problem is that it is difficult to even get reasonable fruits and vegetables that are in season even if you live in a place where they can be grown as no one bothers to grow them anymore.)
I believe the argument they are making is that if the vegetable contains less magnesium, then you have to eat more of it to satisfy that dietary requirement (or your body's craving for it). So the vegetable still has a lot of the other macronutrients but now you have to eat "too many" of the macronutrients to satisfy your micronutrient needs.
In much of the world, "seasonal produce" in winter means essentially nothing fresh: everything had to be preserved from the earlier harvest, and the available methods of preservation were far more destructive (dry, pickle, etc) than today's frozen or canned options, never mind a cool chain than can effortlessly bring you a tropical banana for Christmas in Canada.
> Why not work towards abundant food that is as nutritious as possible?
Because we don't have a silver bullet. We have suggestions. But the world is increasing separating into cheap, low-nutrition food and expensive, nutritious food.
This comment is perfectly alienated from nature. Yes, significant seasonal and regional variation in diet is a worthwhile tradeoff for eating much more nutritious, tastier, cheaper, and more environmentally sustainable food than we have now. No, it does not mean we would have to eat like feudal peasants.
