> The Centers for Disease Control and Prevention found that nearly 10% of all Americans have a nutritional deficiency.
And what about very low, but non-deficient levels?
It very much depends how the study is designed: in this case they do not measure quality of life or disease progression, but clinical outcome. That is what OP was alluding to: if you are going to only look at clinical outcome and completely tar "effectiveness" with that, then that is a very one-sided view of health and well-being.
Osteoporose patients are at increased risk of vitamin K deficiency. Just because multivitamins are not effective at taking us to Mars, are you really going to recommend patients to spend their vitamin money on fresh fruits?