What Determines the Safety of Nutritional Supplements?

The factors that determine the potential for harm resulting from use of a nutritional supplement fall into two categories:

• Excessive Intake
   - acute toxicity due to a massive intake (very rare)
   - chronic toxicity due to a moderately excessive intake from supplements, food or water
      which causes no adverse effects in the short term
  
• Predisposing Factors
   - increased  risk due to the individual’s consumption of alcohol, cigarettes and drugs
   - underlying disease especially liver or renal problems which limit the excretion of any
      excess
   - increasing age of the person altering the balance between benefit and risk
   - genetic factors that alter the metabolism of the nutrient
   - specific interactions with prescription or over-the-counter drugs
      the consumption of prescription drugs was identified as a risk factor for adverse
      reactions to nutritional supplements in a large telephone survey of US citizens
   - sensitivity to the nutrient resulting in an allergic reaction (very rare)

The majority of serious adverse reactions to nutritional supplements can be avoided if a little common sense and caution are used.

Adverse reactions to nutritional supplements that involve chronic toxicity can pass through a number of stages from adequacy to, rarely, death in a similar manner to the evolution of nutritional deficiencies.  Stages of increased intake, increase in tissue stores and then organ dysfunction are the corollary of the stages in the development of a nutritional deficiency [internal link]