characteristics may provide clues that fetuses or infants are particularly susceptible to other supplement ingredients as well. Given these concerns, unless a supplement has been specifically tested for risk during pregnancy or is required for medical reasons, use of dietary supplements during pregnancy cannot be supported.
In addition to life stages that may alter responses to ingested substances, the presence of disease may also result in enhanced susceptibility to adverse effects from particular ingredients. Disease or pre-existing conditions, such as hypertension, cardiac arrhythmias, or other early stages of cardiovascular disease, can be expected to exacerbate susceptibility to substances that specifically affect the organ exhibiting the disease or condition. In conditions such as hepatitis or renal disease, xenobiotic clearance and excretion is markedly altered, allowing compounds that are normally cleared rapidly to accumulate to toxic levels. Similarly, dietary supplement ingredients that affect insulin and glucose regulation are of concern to individuals with diabetes, unless data are available that mitigate this concern.
People who use prescribed medications on a chronic basis, many of which are critically important to their health, may also be at greater risk of harm from interactions of their drugs with various supplement ingredients. For example, people who have HIV/AIDS or other chronic diseases may be taking drug combinations that can interact with supplement ingredients, such as St. John’s wort, that alter cytochrome P450 activity (Ernst, 1999; Piscitelli et al., 2000). (See Chapter 8 for a more detailed discussion on interactions.) Interactions between drugs and dietary supplements may be of particular concern when both are taken for the same pathology and are thus potentially taken at the same time, and possibly without the knowledge of the prescribing physician. For example, vitamin E supplements, which are often recommended to patients with atherosclerotic vascular disease, may interact with statin drugs (Brown et al., 2001).
Certain segments of the population may be particularly susceptible to the effects of some dietary supplement ingredients for a variety of reasons. Factors such as age, disease, pre-existing conditions, ethnicity, sex, or history of specific xenobiotic exposure (such as to drugs or other chemicals,