casein and attempts to demonize milk and animal source foods

http://www.westonaprice.org/bookreviews/chinastudy.html

The China Study:
Startling Implications for Diet, Weight Loss, and Long-Term Health
by T. Colin Campbell
BenBella Books
It was growing up on one of the many dairy farms of the rural American
landscape that the young T. Colin Campbell formed the views that would
shape the early portion of his career. Cow's milk, "Nature's most
perfect food," was central to the existence of his family and
community. Most of the food that Campbell's family ate they produced
themselves. Campbell milked cows from the age of five through his
college years. He studied animal nutrition at Cornell, and did his PhD
research on ways to make cows and sheep grow faster so the American
food supply could be pumped up with more and more protein.1

Fast forward to the present. Campbell is now on the advisory board of
the Physicians' Committee for Responsible Medicine,2 which describes
itself as "a nonprofit organization that promotes preventive
medicine, conducts clinical research, and encourages higher standards
for ethics and effectiveness in research,"3 but whose pro-vegan
agenda reflects its ties to People for the Ethical Treatment of Animals
(PETA) and other animal rights groups, including, according to
Newsweek, Stop Hunting and Animal Cruelty, which the Department of
Justice calls a "domestic terrorist threat."4

Campbell's new book The China Study: Startling Implications for Diet,
Weight Loss, and Long-Term Health hit the bookstores in January 2005
and details the turning points in his post-graduate research that led
Campbell to become a famed opponent of animal foods and an advocate of
the vegan diet. It takes the reader on a tour through Campbell's
early animal experiments, which he interpreted to implicate animal
protein as a primary cause of cancer, through the massive
epidemiological study after which the book was named. Only 39 of 350
pages are actually devoted to the China Study. The bold statement on
page 132 that "eating foods that contain any cholesterol above 0 mg
is unhealthy,"5 is drawn from a broad-and highly selective-pool
of research. Yet chapter after chapter reveals a heavy bias and
selectivity with which Campbell conducted, interpreted, and presents
his research.


Protein and Cancer
The first strike against the pro-protein mantra Campbell had inherited
from his nutritional forbears came while he was studying the
relationship between aflatoxin (AF), a mold-related contaminant often
found in peanut butter, and cancer in the Philippines. Campbell was
informed by a colleague that, although the areas with the highest
consumption of peanut butter had the highest incidence of liver cancer,
it was the children of the "best-fed families," who consumed the
most protein, who were getting liver cancer. Whether the best-fed
Philippino families ate the many staples of modern affluent diets like
refined breads and sugars isn't mentioned.6

This observation was corroborated by a study published in "an obscure
medical journal," that fed AF to two groups of rats, one consuming a
5 percent protein diet, one consuming a 20 percent protein diet, in
which every rat in the latter group got liver cancer or its precursor
lesions, and none in the former group got liver cancer or precursor
lesions.7

Campbell went on to investigate the possible relationship between
nutritional factors, including protein, and cancer, a study that
proceeded for 19 years with NIH funding.8 His conclusion was
revolutionary and provocative: while chemical carcinogens may initiate
the cancer process, dietary promoters and anti-promoters control the
promotion of cancer foci,9 and it is nutritional factors, not chemical
carcinogens, that are the ultimate deciding factors in the development
of cancer.10 Yet the 19 years of research into this project leave us
with more questions than answers, and have left T. Colin Campbell with
a foundation of unsupported conclusions upon which he has built his
tower of vegan propaganda.

Campbell began his studies using AF as an initiator of cancer foci and
the milk protein casein as the promoter protein of study. His results
corroborated the earlier results of other researchers: a dose-response
curve existed for AF and cancer on a 20 percent casein diet, but
disappeared on a 5 percent protein diet.11 He found that adjusting the
protein intake of the same rats could turn cancer promotion on and off
as if with a switch,12 and found casein to have the same effect when
other cancer initiators, such as the hepatitis B virus, were used.13

Rather than throwing a blanket accusation at all protein, Campbell
acknowledged that the study of other proteins would be required before
generalizing, just as the study of other cancer initiators would be
required before generalizing to them. Wheat and soy protein were both
studied in lieu of casein, and both were found not to have the
cancer-promoting effect of casein.14 Amazingly, Campbell's reluctance
to make unwarranted generalizations ends here. After briefly describing
some research finding a protective effect of carotenoids against
cancer, Campbell concludes the chapter on his animal research by noting
the following overarching pattern: "nutrients from animal-based foods
increased tumor development while nutrients from plant-based foods
decreased tumor development."15 (His italics.)

The generalization from the milk protein casein to all "nutrients
from animal-based foods" is clearly unwarranted. If Campbell took
caution to study the issue further before generalizing from casein to
all proteins, why didn't he take the same caution before generalizing
from casein to all animal proteins or all animal nutrients? Indeed,
Campbell later acknowledges that he is making this generalization: ".
.. . casein, and very likely all animal proteins, may be the most
relevant cancer-causing substances that we consume."16 Why this
generalization is "very likely" to be true is left unexplained.

Campbell is aware that casein has been uniquely implicated in health
problems, and dedicates an entire chapter to casein's capacity to
generate autoimmune diseases.17 Whey protein appears to have a
protective effect against colon cancer that casein does not have.18 Any
effect of casein, then, cannot be generalized to other milk proteins,
let alone all animal proteins. Other questions, such as what effect
different types of processing have on casein's capacity to promote
tumor growth, remain unanswered. Pasteurization, low-temperature
dehydration, high-temperature spray-drying (which creates carcinogens),
and fermentation all affect the structure of casein differently and
thereby could affect its physiological behavior. What powdered,
isolated casein does to rats tells us little about what traditionally
consumed forms of milk will do to humans and tells us nothing that we
can generalize to all "animal nutrients." Furthermore, Campbell
fails to address the problems of vitamin A depletion from excess
isolated protein, unsupported by the nutrient-dense fats which
accompany protein foods in nature.

Lessons from China
In the early 1980s, along with Chen Junshi, Li Junyao, and Richard
Peto, T. Colin Campbell presided over the mammoth epidemiological study
referred to as the China Project, or China Study. The New York Times
called it "the Grand Prix of epidemiology," and it gathered data on
367 variables across sixty-five counties and 6,500 adults. Amazingly,
from over 8,000 statistically significant associations, Campbell was
able to draw a single unifying principle: "People who ate the most
animal-based foods got the most chronic disease. . . . People who ate
the most plant-based foods were the healthiest and tended to avoid
chronic disease."19

The study utilized recall questionnaires, direct observation and
measurement of intakes over a three-day period, and blood samples.20
The blood samples were combined into large pools for each village and
each sex.21 This had the drawback of dramatically decreasing the number
of data points relative to the enormous number of correlations being
generated, and the advantage of allowing the blood to be tested for
many, many more variables than would be testable using individual
samples.

One of the benefits of the China Study's design was that the genetic
stock of the study subjects had little variation, while there was wide
variation among cancer and other disease rates. While the dietary
surveys were conducted in the autumn of 1983,22 the mortality rates
were taken a decade earlier in 1973 through 1975.23 Rural areas were
thus deliberately selected to ensure that the people in the area had
for the most part lived in the area all their lives and had been eating
the same foods native and traditional to that area, so that the
mortality data would reliably match the dietary data.

One of the drawbacks of the study was that nutrient intakes were
determined from food composition tables, rather than measured directly
from foods.24 This disallowed any consideration of differences in
nutrient composition of foods within the area due to soil quality,
which was a primary theme of Weston Price's research. Another
drawback was that the questionnaire did not adequately account for the
diversity of animal foods in the Chinese diet. Questions about the
frequency of consumption of sea food, meat, eggs, and milk were
included, but questions about organ meats and insects were not included
on the questionnaire, nor was fish differentiated from shell fish,
despite the very different nutrient profiles of these foods.25
Additionally, the autumn dietary survey could not take into account
foods that were not in season at the time.

What is most shocking about the China Study is not what it found, but
the contrast between Campbell's representation of its findings in The
China Study, and the data contained within the original monograph.
Campbell summarizes the 8,000 statistically significant correlations
found in the China Study in the following statement: "people who ate
the most animal-based foods got the most chronic disease."26 He also
claims that, although it is "somewhat difficult" to "show that
animal-based food intake relates to overall cancer rates," that
nevertheless, "animal protein intake was convincingly associated in
the China Study with the prevalence of cancer in families."27

But the actual data from the original publication paints a different
picture. Figure 1 shows selected correlations between macronutrients
and cancer mortality. Most of them are not statistically significant,
which means that the probability the correlation is due to chance is
greater than five percent. It is interesting to see, however, the
general picture that emerges. Sugar, soluble carbohydrates, and fiber
all have correlations with cancer mortality about seven times the
magnitude of that of animal protein, and total fat and fat as a
percentage of calories were both negatively correlated with cancer
mortality. The only statistically significant association between
intake of a macronutrient and cancer mortality was a large protective
effect of total oil and fat intake as measured on the questionnaire. As
an interesting aside, there was a highly significant negative
correlation between cancer mortality and home-made cigarettes!28

Campbell's case for the association between animal foods and cancer
within the China Study is embedded within an endnote. Campbell states:
"Every single animal protein-related blood biomarker is significantly
associated with the amount of cancer in a family."29 Following the
associated endnote, these biomarkers were "plasma copper, urea
nitrogen, estradiol, prolactin, testosterone, and, inversely, sex
hormone binding globulin, each of which has been known to be associated
with animal protein intake from previous studies."30

Since Campbell does not cite these "previous studies," the reader
is left in the dark regarding the reliability of his assumptions. Blood
biomarkers are generally associated with food intake patterns, rather
than specific foods. Since food intake patterns differ in different
populations, an association found between a biomarker in one population
cannot be necessarily generalized to another.31 For example, people who
eat more whole grains might have higher levels of vitamin C, even
though whole grains do not contain vitamin C. This might be true in one
population where people who eat whole grains tend to eat more fruits
and vegetables, but untrue in another population. It isn't at all
clear why this roundabout way of measuring animal protein consumption
is superior to the direct methods of the study, such as the food
questionnaire and the dietary observations.

Additionally, of the biomarkers measured, estradiol only had a
statistically significant relationship with animal protein in women
under 45, as is true for sex hormone-binding globulin, both of which
had negative correlations in women aged 55-64. There was no
statistically significant relationship between animal protein and
testosterone in men of any age, which were negatively correlated in all
age groups, nor in females except those aged 55-64. Plasma prolactin
was only statistically significantly related to animal protein
consumption in the oldest group of females, and was negatively
correlated in other age groups.32 Only urea nitrogen and copper were
consistent and significant indicators of animal protein consumption,
and of these two only copper was significantly related to cancer
mortality.33

It is difficult to see how Campbell can so emphatically draw the
conclusion that animal foods are the cause of most diseases from this
data.

Only Half the Story?
By the title, one would expect The China Study to contain objective and
complete information derived from the China Study. Page one touts
"real science" above "junk science" and "fad diets." Yet
Campbell consistently presents only half the story at best through the
duration of the book. In Part II, Campbell presents the evidence
incriminating animal products as the cause of nearly every disease. He
cites several health care practitioners, including Dr. Caldwell
Esselstyn Jr. and Dr. Dean Ornish, who claim to have been able to
reverse heart disease with plant-based diets,34 and cites the Papua New
Guinea Highlanders as an example of a traditional society without the
occurrence of heart disease, but makes no mention of George Mann's
and other researcherS' extensive study of the Masai or the healthy
primitives of Weston Price. That the programs of Ornish and Esselstyn
involved more than abstention from animal foods-especially the
program of Ornish, of which diet is only a small part-is not seen as
a confounding factor that detracts from our ability to incriminate
animal foods in heart disease. Nor does he bother to mention the
cannibalism or the swollen bellies of children that accompanies the
protein-starved diet of the New Guinea Highlanders.35

In Campbell's discussion of diabetes, he concludes that
"high-fiber, whole, plant-based foods protect against diabetes, and
high-fat, high-protein, animal-based foods promote diabetes."36 He
discusses the possible role of cow's milk in causing Type 1 diabetes
via an autoimmune reaction,37 but makes no mention that wheat gluten
has been implicated in Type 1 diabetes by a similar process.38 He
similarly fails to mention the role of fructose consumption in causing
insulin resistance,39,40 and the increase in high fructose corn syrup
consumption that has paralleled the increase in diabetes.

Campbell discusses the role of animal foods in causing prostate
cancer,41 but makes no mention of the potent preventative role current
research is attributing to vitamin A, a nutrient found in animal
foods.42 He devotes 19 pages to discussing the role of cow's milk in
causing autoimmune diseases,43 but zero pages to the role of wheat
gluten in causing autoimmune diseases.44 Campbell suggests that dietary
fat and cholesterol contribute to Alzheimer's and discusses the
potential protective effects of plant foods,45 but makes no mention of
the protective effect of DHA, an animal-based nutrient, currently under
investigation.46

The China Study frequently ignores the contribution of animal foods to
certain classes of nutrients, such as B vitamins and carotenes. Both
classes of nutrients are assumed to come from plant foods, despite egg
yolks and milk from pastured animals being a good source of carotenes,
and the high B vitamin content of liver. But the most curious of such
statements is one found on page 220, where Campbell declares, "Folic
acid is a compound derived exclusively from plant-based foods such as
green and leafy vegetables."47 This is a fascinating statement,
considering that chicken liver contains 5.76 mcg/g of folate, compared
to 1.46 mcg/g for spinach!48 A cursory look through the USDA database
reveals that the most folate-dense foods are organ meats.

The China Study contains many excellent points in its criticism of the
health care system, the overemphasis on reductionism in nutritional
research, the influence of industry on research, and the necessity of
obtaining nutrients from foods. But its bias against animal products
and in favor of veganism permeates every chapter and every page. Less
than a page of comments are spent in total discussing the harms of
refined carbohydrate products. Campbell exercises caution when
generalizing from casein to plant proteins, but freely generalizes from
casein to animal protein. He entirely ignores the role of wheat gluten,
a plant product, in autoimmune diseases, so he can emphasize the role
of milk protein, an animal product. The book, while not entirely
without value, is not about the China Study, nor is it a comprehensive
look at the current state of health research. It would be more aptly
titled, A Comprehensive Case for the Vegan Diet, and the reader should
be cautioned that the evidence is selected, presented, and interpreted
with the goal of making that case in mind.

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TC

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