This is a problem with supplementation !! It would be a great world if we could get all we need from the food we eat! This is why I also believe that nutrient supplementation works much better with the full spectrum of amino acids or minerals! Supplementing with single elements does'nt help much at all, the same with amino acids! There is also a synergy at work here between amino acids and minerals!
If one must supplement as is the case in our modern world then supplement wisely!