Dietary supplements and fortified foods are used to ensure adequate dietary intake of important vitamins and minerals.While dietary supplements and fortified foods can be helpful and even necessary, in many situations, they could lead to excessive vitamins intake and other negative side effects if consumed in excessive amounts. This is because there are differences between the synthetic vitamins found in supplements and fortified foods and the nutrients naturally contained within the foods you eat. This article explains the differences between natural and synthetic vitamins.