On this website they discuss how the labeling requirements on supplements are misleading. A label might be able to say that it only contains vitamin D and in other ingredients list only gelatin capsules but in fact have added fillers. This is because manufacturers only have to list on the label what they themselves have put in, not what products were in what they purchased from others. In the example above, the vitamin D could have been pure or be a 0.1%dilution in a base of dicalcium phosphate, lactose, acacia, BHT, sodium benzoate, and sorbic acid. If you are taking a multivitamin every ingredient could contain just as many fillers. I don’t have to explain how dangerous this is for people with sensitivities and allergies.
I currently take several supplements. I did research them and the companies have good reputations, however it’s always a risk. For the most part I choose to buy my supplements in bulk and stuff my own pills but it’s been worth the risk for me during nursing to increase my nutrition with prenatal vitamins and a B supplement because I have difficulty consuming enough nutrition via food alone. Some people really don’t have that luxury and I feel that no matter how difficult it would be for manufacturers, that all ingredients should be required by law to be listed on the label.