most commonly associated with the sublime experience of the European
spa. Visitors have been masked, soaked, and basted with this touted
curative since the Romans ruled. But go back further still and you’ll
find that clay has had a role in human health as ancient as man.
The first proof of the
therapeutic use of clays was incised on clay tablets in Mesopotamia
around 2500 B.C. However, some scholars believe that prehistoric
ancestors such as Homo erectus and Homo neanderthalensis
used ochres to cure wounds as well as paint caves. Ochres are a
mixture of clay and iron hydroxides.
In Egypt, Cleopatra
used clays to preserve her complexion. But the Pharaohs’ physicians
used the material as anti-inflammatory agents and antiseptics. It was
also an ingredient used for making mummies.
Despite a long
history of use, some very fundamental questions remain about the
benefits of clay.
Can clays cure? At
Arizona State University, geochemist Lynda Williams and microbiologist
Shelley Haydel have teamed up to find out. If their research into the
antibacterial properties of clays realizes its full potential,
smectite clay might one day rise above purely cosmetic use. It might
take its place comfortably with antibacterial behemoths like
interested in natural cures and I think that there is a lot of nature
that we don’t understand yet,” Williams says. “What if we unearth a
mechanism for controlling microbes that had never been discovered
before? It is these avenues, at the boundaries of scientific
discovery, at the edges of my field and knowledge (and Shelley’s),
where such discoveries are made.”
Williams and Haydel’s
research is an unusual pairing. Both work in the College of Liberal
Arts and Sciences. But both are pursuing different lines of scientific
Williams is an
associate research professor in the School of Earth and Space
Exploration. She studies clay geochemistry. Haydel is an assistant
professor in the School of Life Sciences and with the Center for
Infectious Disease and Vaccinology in the Biodesign Institute. She
This disparate duo is
attempting to tease apart the mechanisms that allow two clays mined in
France to heal Buruli ulcer. The flesh-eating bacterial disease is
found primarily in central and western Africa.
Buruli ulcer has been
declared to be “an emerging public health threat” by the World Health
Organization (WHO). Mycobacterium ulcerans is the bacterium
that causes Buruli ulcer. It is related to the microorganisms that
cause leprosy and tuberculosis. The bacterium produces a potent toxin
that causes necrotic lesions. It destroys the fatty tissues under the
“The toxin is
immunosuppressant. Patients feel no pain and the body mounts no
response to infection. It leads to disfigurement and isolation, not
unlike that seen in leprosy,” Haydel explains. “Traditional
antibiotics can only make a difference at the very earliest stages of
the disease. As a result, past treatments have been largely confined
to amputations or surgical excision of the infected sites.”
If the clays being
studied actually are antibacterial in nature, and the reason for that
activity can be isolated, the ASU scientists say they may represent a
new form of topical treatment. It would be a treatment that goes
beyond the capacity of existing antibiotics.
“They could be
produced and distributed cheaply and easily stored,” Williams says.
That would make them ideal for use in developing countries.
So how did a clay
specialist with a background in low temperature geochemistry become
involved with a health care project centered in the Ivory Coast? It
was the result of the scientific equivalent of an online dating
“I answered a posting
on the Clay Minerals Society list serve placed by Thierry Brunet de
Courssou. He was asking to have someone take high resolution scanning
electron micrographs of the clays,” Williams explains. “I confess that
we all ignored him initially.”
According to the
Brunet de Courssou Web site, the family operates health clinics on the
Ivory Coast and in New Guinea. For a decade, Madame Line Brunet de
Courssou, Thierry’s mother, had been importing two French clays to
treat people with Buruli ulcer. She was getting startling results,
while her use of native clays had no effect.
Williams reviewed the
mother’s work and says that “Line Brunet de Courssou was a careful
However, she was not
a scientist. The mother is now deceased. But in 2002, she approached
the WHO during its fifth advisory group meeting on Buruli ulcer. She
had documented more than 50 cases of successful healing with the clay
treatments. WHO documents indicate that the organization was
receptive. They called her results “impressive.” But Williams says
that funding was denied for lack of scientific study.
Williams is from a
family of physicians. She says that it was really the second message
that finally drew her to the project.
“Brunet de Courssou
wrote, ‘I guess that no American scientists are interested in helping
poor people in Africa.’”
He guessed wrong.
Williams got 100 grams of the clay in green powder form. She took the
requested micrographs of the minerals. She also went a step further
and examined their crystal structure and chemical compositions.
contacted and recruited Haydel to the project before the
microbiologist actually arrived at ASU in 2005. Haydel brought more
than 13 years of experience working with pathogenic bacteria, in
particular tuberculosis, to the project.
“I approached this
work from the viewpoint of a clinical microbiologist,” Haydel says. “I
ordered bacterial strains that pharmaceutical companies use to test
Haydel tested both of
the French clays that Brunet de Courssou had been importing. One
completely inhibited pathogenic
Escherichia coli, Salmonella typhimurium and Pseudomonas
aeruginosa, often a problem as an opportunistic infection in burn
wards. It stopped Mycobacterium marinum (related to
Mycobacterium ulcerans) as well.
The clay also
partially inhibited the growth of pathogenic Staphylococcus aureus,
including a multi-drug resistant variety.
“The other clay
actually helps the bacteria to grow,” Haydel adds.
What makes one clay kill bacteria, and the other promote growth? And
why do most clays tested have no effect? Williams and Haydel hope that
their research will answer these and other questions.
“Clay can be as
variable as the bacteria we are studying. There is a lot to be learned
yet,” Williams says,
fascination with clay started when she was a mineral exploration
geologist looking for ore deposits. She worked at Dartmouth College
with Bob Reynolds, “the father of clay mineralogy.” She later worked
as a research associate at Louisiana State University. A colleague
there was studying geophasia – eating clay. The behavior has been seen
in animals and people since the time of the aborigines.
“In the South
Appalachian Mountains, poor women would eat the local clay to help
soothe nausea and stomach ailments, particularly during pregnancy,”
Williams explains. “The clay was rich in kaolinite. (Kaolinite is the
major ingredient in the over the counter remedy Kaopectate). But one
day, they ran out of clay and moved over to another mountain and
people began dying. We wanted to know why.”
Not all clays are
alike. The key to clay’s variable nature seems to be its physical
“Clay is a mineral.
It has a crystalline structure that is both flexible and fluid,”
Williams says. She likens them to very thin, two-nanometer-thick
slices of bread in a peanut butter and jelly sandwich.
The “bread” is
composed of three regions. Two silicate layers with tetrahedral rings
surround an octahedral core. The “peanut butter” is the charged
cations. For example, potassium ions stick to the negatively charged
tetrahedral ring surface.
And the “jelly”?
Organic compounds or other species of any or no charge are possible.
In a clay sandwich, the peanut butter and jelly are called the
interlayer. The interlayer can vary in width and composition depending
on the kinds of water and elements present when it was formed.
The ASU scientists
say that it is this interlayer where much of the elemental variability
between clays can be found. And the interlayer surface area is huge.
Each gram of clay contains hundreds of square meters of surface area.
As a result, surface chemical reactions from these sites have an
enormous impact on the geochemistry of the local environment.
passionate about her subject. “Clays are as individual in character as
people are in personality,” she says. “They can be as old as
Precambrian times—anywhere from 700 million to 4.6 billion years ago.
They are probably older, since meteorites contain clay minerals from
other celestial bodies. Or they can be as young as the clays I made in
my lab few hours.”
Clays form when the
chemistry, temperature, and pressure conditions are right, Williams
continues. “In the case of the two French clays we are testing, their
bulk chemical structures are almost identical. But the different trace
element chemistry of the interlayer records differences in the
depositional environment where the antimicrobial property was likely
the interlayer, the way other materials, metals, or ions bind to
clays, the absorptive characteristics of clays; all are important. All
could potentially play a role in the antibacterial activity the
scientists find in the one French clay.
suggest that the antibacterial activity is associated with the
interlayer. But Williams says that crystal size and surface properties
may also play a role. It is a mystery that engages both research
Haydel says. “Here we are bridging geology, microbiology, cell
biology—transdisciplinary sciences. A year ago, I’d look at the clay
and say, ‘well that’s dirt.’ Now I know a little something about clay
structure and Lynda knows a little bit about microbiology. Alone, we
each would have had to study for years. Together we are partnering
these disciplines with synergy that really works.”
Williams and Haydel
both expect to find the key to the mystery of what makes this French
green clay heal.
Haydel adds: “I had a
professor in graduate school say, ‘Maybe perhaps once in your life, in
your scientific career, you’ll come across something that can change
the world.’ Sometimes I think: This is it!”
the healing properties of clay is supported by the National Center for
Complementary and Alternative Medicine at National Institutes of
Health (NCCAM). NCCAM was established in 1998 to fund scientific
research and technologies that fall outside conventional medicines.
For more information, contact Lynda Williams, Ph.D., School of Earth
Science & Space Exploration, 480.965.0829. Or Shelley Haydel, Ph.D.,
Biodesign Institute, 480.727.7234. Send e-mail to
Lynda.Williams@asu.edu or to