The following HTML text is provided to enhance online
readability. Many aspects of typography translate only awkwardly to HTML.
Please use the page image
as the authoritative form to ensure accuracy.
Dietary Supplements: A Framework for Evaluating Safety
graph and in Chapters 4 and 6, the similarity of a product form greatly impacts the chemical constituents consumed, and apparent safety associated with one form should not be extrapolated to another form. Specifically, in the case of chaparral, NDGA concentrations are likely to be higher in chaparral products that are not water-extracted teas. Only one of the human adverse events appeared to be associated with chaparral tea use. Thus the integrative evaluation distinguished between safety problems associated with chaparral consumption as a tea and safety problems associated with other chaparral products likely to contain more NDGA.
Animal data included studies about NDGA. They suggested that chaparral and NDGA administration result in anti-implantation activity or inhibition of ovulation and increase resorption of fetuses, respectively. As indicated in Chapter 5, the animal reproductive toxicity effects were deemed particularly important to consider because it is unlikely they would be detected by human use, even with long-term traditional use (see Chapter 4 discussion of “Considering the Relevance of Historical Use” ). Also important to the consideration of liver toxicity was the information uncovered about kidney damage, which in addition to indicating a potential risk for renal toxicity might also suggest harm at other sites of NDGA metabolism, such as the liver.
In vitro data relevant to the safety of chaparral were also considered. In vitro studies on NDGA provided mechanistic information, such as lipoxygenase and cyclooxygenase inhibition and inhibition of prostaglandin synthesis.
Information about the safety of related substances and the chemical structure of chaparral constituents raised two possible concerns. First, NDGA is functionally related (see Chapter 8) to prostanoid pathway inhibitors, which are contraindicated during the first and third trimesters of pregnancy. Second, the chemical structure of NDGA indicates that it is likely to be a substrate for cytochrome P450-dependent quinone formation. Finally, in vitro data suggest NDGA is functionally related to 5-α-reductase inhibitors, which are contraindicated in pregnancy due to effects on male development in utero.
Finally, the totality of information summarized above is considered according to the scientific principles for evaluating and integrating data, as described in Chapter 10. As stated in Chapter 10, “In the absence of scientific studies designed specifically to test safety of a dietary supplement, concern for public safety may be raised by the presence of even a few reports of possible safety concerns, when viewed together and constituting the weight of available evidence.” No scientific studies designed specifically and adequately to test the safety of chaparral were found. The information suggesting safety is limited to the possible historical use of chaparral without documented adverse effects. The information suggesting risk of NDGA-