Safety and balance are two reasons that people should choose a professionally formulated, broad-spectrum nutritonal supplement, rather than ordering a la carte. While the chance of accidental overdose is small, some combinations of nutrients can inhibit or heighten a stand-alone supplement, can upset the metabolism of other minerals in the body. High levels of vitamin C and citric acid can dramatically increase the uptake of iron, a mineral well known for its cumulative toxicity. Taking a high-dose iron supplement in combination with high levels of vitamins C could pose a significant health risk for the unsuspecting consumer.
To be frank about it, the average consumer has limited ability to select the individual nutrients in their most bioavailable forms and dispense them in appropriate and balanced amounts. It is far better to purchase a professionally designed broad-spectrum nutritional supplement in which the questions of completeness, potency, balance and synergy have been factored into the formulation.