I think the point is that any diet related comment should probably be prefaced with: speak to a doctor, dietician; have a blood test done to test levels. From what I recall, zinc, magnesium and vitamin D could all reach sufficient levels just from diet, and, having too much of any of these can have bad results. Therefore someone who simply follows every and any diet suggestion on forums could possibly be at risk - despite a goodhearted, scientifically founded suggestion.