Livestock are very sensitive to changes in the nutrient density of their food. I learned this in technical school (BCIT). Working with ranchers, selling feed and doing organic inspections, got me noticing what supplements they were using, like Zinc. If the soil could not produce enough zinc for livestock growth and development, was it good for human food? Decades of increasing amounts of chemical fertilizer on food producing land has dramatically lowered the nutrient density of supermarket food (see Davis 2009 study in Hort Science).
Low nutrient density food is not good for human health, as present trends indicate. What else, besides nutrient density, makes food healthy?