As the soil grows healthier, the food supported by that soil contains more minerals and nutrients, which also helps animals grow and be healthy. Likewise, the health benefits of grassfed products have also been documented.
Grass fed beef contains more vitamins, minerals and antioxidants than grain fed beef. Research has shown grass fed beef has increased levels of beta-carotene, which is a precursor to vitamin A. Higher levels of cancer fighting antioxidants (vitamin E, glutathione and superoxide dismutase) have also been attributed to grass fed beef. Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2846864/