I'm glad this is something that's being looked at, but it's too soon to say what the actual effects are. As the article points out, we simply don't know what kind of actual effects this will actually have for human health. For example, how much of it is offset by the fact that we actually have access to a variety of foods that was unthinkable before refrigeration? A lot of foods have vitamins added to them as well. One thing that it does suggest is that all those concerns about a Malthusian Trap may not be behind us.
The greater concern, I think, is the impact on other species of a change in the nutrient content of their food. Ecosystems can be quite fragile and such a shift could have ramifications we can't foresee. Food chains may break down. And all this takes place in ecosystems that are already stressed due to temperature change, atmospheric change, the effects of agriculture, ocean acidification, ocean deoxygenization, etc. We're applying so much stress across the whole planet that it's unpredictable where breakages are going to take place. The nutrient issue is one more source of stress, and one more reminder that these systems are so complex that our actions have unpredictable effects.
Vitamins added to food are often not in a form that the human body can make use of. Heck, vitamins not added to food are often not in a form that the human body can make use of. Also, vitamins added are vitamins discovered. There are all sorts of nutritional aspects of food that known vitamins don't address.