Saying Chinese Herbs Cause Cancer Equals Bad Science

Recently the article Alternative Medicine Warning:Confounding variables
Some Chinese Herbs May Increase Cancer Risk cameIn stastical analysis, a confounding variable is
to my attention. The Fox News report reviews ansomething that relates to both the dependent and
academic article published by the Journal of theindependent variable. Study methodologies need to
National Cancer Institute. Having more than a passingcontrol for confounding variables in order to avoid
interest in Chinese herbal medicine, I chased downmaking invalid inferences about the relationship of the
the original article, Population-Based Case-Controlvariables being studied.
Study of Chinese Herbal Products ContainingFor example, suppose a study wants to determine if
Aristolochic Acid and Urinary Tract Cancer Risk (Lai,performing regular weight-bearing exercise is an
Wang, et. all). The authors conclude, "Consumption ofeffective way to prevent osteoporosis in
aristolochic acid-containing Chinese herbal productspost-menopausal women. Women are selected for
[mu tong] is associated with an increased risk ofthe study and categorized as either doing the
cancer of the urinary tract in a dose-dependentexercise or not. But suppose also that the women in
manner that is independent of arsenic exposure."the weight-bearing exercise also regularly take a
A long time student of mathematics and a morecalcium supplement, which is known to prevent
recent student of public health and biostatistics, I setosteoporosis. Without taking this fact into
about critically analyzing this paper. I have twoconsideration and making appropriate statistical
observations that cause me to personally call toadjustments, analysis might incorrectly conclude that
question the validity of the authors' conclusion.the weight-bearing exercise had a greater role in
Which herb are they talking about?preventing osteoporosis than it actually did.
In traditional Chinese herbal medicine, there are twoIn the study concerning mu tong, the authors
different herbs that are colloquially referred to as muconsidered and accommodated for the presence of
tong. Guan mu tong, or aristolochia, containssignificant levels of arsenic in the subjects' drinking
aristolochic acid, a known nephrotoxin. In modernwater (arsenic is known to cause urinary tract
practice, this herb is rarely used and is banned fromcancer). However, the authors site in their limitations
importation to the United States by the Food &section that smoking status was not considered
Drug Administration (FDA). Chuan mu tong, or caulisduring analysis. Personally, I have reviewed many
mutong, on the other hand is not known to containarticles regarding cancer and possible causative
aristolochic acid. Chuan mu tong is effectively used toagents and I cannot think of one that was
treat urinary tract infections and promote lactation inconsidered authoritative in which smoking tobacco
cases of blocked milk ducts.products, a well established carcinogenic habit, was
The authors of the study make no distinction in theirnot considered and controlled for.
report if they are reviewing cases of people usingPersonally, I am appalled to think that a combination
chuan mu tong or guan mu tong, though consideringof poorly designed scientific research and irresponsible
their interest in aristolochic acid, I would guess theyjournalism could lead people to the conclusion that
are studying the potentially carcinogenic effects ofChinese herbs cause cancer. Herbs, like all things we
guan mu tong. Considering that guan mu tong isingest, need to be scrutinized for their quality and
neither legal nor widely available for use, I questioneffects, but to shut the door on all Chinese herbs is
why Fox news took such an interest in thisa terrible mistake.
publication initially.