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 All Thumbs Book Reviews
The China Study: Startling Implications for Diet, Weight Loss, and
Long-Term Health
By T. Colin Campbell
BenBella Books
Review By Chris Masterjohn
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.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.
REFERENCES
1. Campbell, T. Colin, PhD, with Thomas M. Campbell II, The China
Study: Startling Implications for Diet, Weight Loss, and Long-Term Health,
Dallas: BenBella Books, 2004, p. 4.
2. http://www.pcrm.org/about
3. http://www.pcrm.org
4. http://www.activistcash.com/organization_overview.cfm/oid/23
5. Campbell, p. 132.
6. Ibid, p. 36.
7. Ibid, pp. 36-37.
8. Ibid, p. 48.
9. Ibid, p. 50.
10. Ibid, p. 56.
11. Ibid, p. 59.
12. Ibid, p. 62.
13. Ibid, p. 63.
14. Ibid, p. 60.
15. Ibid, p. 66.
16. Ibid, p. 104.
17. Ibid, p. 183-201.
18. Hakkak, et al., "Dietary Whey Protein Protects against Azoxymethane-induced
Colon Tumors in Male Rats," Cancer Epidemiology Biomarkers
& Prevention, Vol. 10, 555-558, May 2001.
19. Campbell, p 7.
20. Campbell, p. 73.
21. Ibid, p. 355.
22. Junshi, Chen, T. Colin Campbell, Li Junyao, and Richard Peto, Diet,
Life-style and Mortality in China: A Study of the Characteristics of
65 Chinese Counties, Oxford: Oxford University Press, 1990, p.
6.
23. Ibid, p 1.
24. Ibid, p. 16.
25. Ibid, p. 850.
26. Campbell, p. 7.
27. Ibid, p. 88.
28. Junshi, p. 106.
29. Campbell, p. 89.
30. Ibid, p. 376.
31. Ness, et al., "Plasma Vitamin C: What Does it Measure?"
Public Health Nutr., 1999 March 2 (1):51-4.
32. Junshi, p. 572.
33. Ibid, p. 106.
34. Campbell, 125-130.
35. Diamond, Jared, Guns, Germs, and Steel: The Fate of Human Societies,
New York: W. W. Norton & Company, 1999, p 149.
36. Campbell, p 151.
37. Ibid, p. 146.
38. Braly, James, M.D., and Ron Hoggan, M.A., Dangerous Grains,
New York: Penguin Putnam, 2002, p. 124.
39. Mayes, Peter A., "Intermediary Metabolism of Fructose,"
Am J Clin Nutr 1993;58(suppl):754S-65S.
40. Hollenbeck, Clarie B., "Dietary Fructose Effects on Lipoprotein
Metabolism and Risk for Coronary Artery Disease," Am J Clin
Nutr 1993;58(suppl):800S-9S.
41. Campbell, p. 177-182.
42. McCormick, et al., "Chemoprevention of rat prostate carcinogenesis
by 9-cis-retinoic acid," Cancer Res. 1999 Feb 1;59(3):521-4.
43. Campbell, pp. 183-201.
44. Braly, 117-133.
45. Campbell, p 220.
46. Calon, et. al., "Dohosahexaenoic Acid Protects from Dendritic
Pathology in an Alzheimer’s Disease Mouse Model," Neuron,
Vol 43, 633-645, 2 September 2004
47. Campbell, p 220.
48. USDA National Nutrient Database for Standard Reference, Release
17.
Figure 1: Associations of Selected Variables
with Mortality for All Cancers
| Total Protein |
+12% |
|
Carbohydrates |
+23% |
| Animal Protein |
+ 3% |
|
Total Calories |
+16% |
| Fish Protein |
+ 7% |
|
Fat % Calories |
- 17% |
| Plant Protein |
+12% |
|
Fiber |
+21% |
| Total Lipids |
- 6% |
|
Fat (questionnaire) |
- 29%* |
| * statistically significant |
** highly significant |
*** very highly significant |
About the Author
 Chris
Masterjohn is the author of several Wise Traditions articles
and the creator and maintainer of Cholesterol-And-Health.Com,
a website dedicated to extolling the virtues of cholesterol and cholesterol-rich
foods. He has authored two items accepted for publication in peer-reviewed journals:
a letter in an upcoming issue of the Journal of the American College of
Cardiology criticizing the conclusions of a recent study on saturated fat
and a full-length feature in an upcoming issue of Medical Hypotheses
proposing a molecular mechanism of vitamin D toxicity. Masterjohn holds a Bachelor's
degree in History and is preparing to pursue a PhD in Molecular and Cellular
Biology. He is also a Weston A. Price Foundation Local
Chapter Leader in West Brookfield, Massachusetts.
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