The Breast Cancer Prevention Diet by Dr. Bob Arnot: Unscientific and Deceptive A Disservice to American Women

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A Position Paper from the American Council on Science and Health prepared by John Morgan, DrPH1,2, Shalu Sharma, BS1 and Alicia Lukachko, M.P.H.3 And the Staff of the American Council on Science and Health

1Loma Linda University, School of Public Health
2Region 5 of the California Cancer Registry
3American Council on Science and Health

Position Statement

This report presents a critical review of The Breast Cancer Prevention Diet, a new book by NBC s chief health correspondent, Dr. Bob Arnot. In this review the scientists of the American Council on Science and Health (ACSH) express their profound concern about the misleading, unscientific, and speculative advice that Dr. Arnot offers to women who wish to reduce their risk of breast cancer, and to women who wish to maximize their chances of survival once they have been diagnosed with the disease: i.e., to all women.

ACSH believes, first, that in the absence of sound, peer reviewed evidence supporting such advice, there is harm in recommending lifestyle modifications for the purpose of preventing breast cancer. ACSH also believes that a physician and particularly one in a position of public trust, such as a professional media health expert should refrain from selling advice based on the twin philosophies that you can t afford to wait for the evidence, and that you can only improve your health with this diet. Indeed, unproven interventions such as those put forth in this book can have negative effects on both physical and psychological health.

The American Council on Science and Health contacted many of the scientists quoted or cited in Dr. Arnot s book. Some expressed concerns regarding the book s message, and/or the misrepresentation of their work. None of the physicians or scientists contacted by ACSH, however, would comment for the record. Memorial Sloan Kettering Cancer Center in New York, as a result of complaints from its physicians that they were misquoted and their research misrepresented, communicated its concerns to the book s publisher Little Brown. Dr. Arnot then agreed to omit all references to Memorial Sloan in future editions of the book.

The MSKCC public relations office acknowledged that the Center had serious concerns about the Arnot book and that these concerns had been conveyed to the publisher, Little, Brown and Co., and to Dr. Arnot. The MSKCC representative noted that Dr. Arnot had graciously agreed to delete all references to Memorial Sloan Kettering Cancer Center from future editions.

The American Council on Science and Health:

  • respectfully requests that the producers of NBC s Today and other major television programs that have promoted Dr. Arnot s book offer airtime to scientific and medical authorities who are qualified to critique Dr. Arnot s unproven recommendations; and
  • calls upon medical and health professionals in the fields of nutrition, cancer treatment and prevention, and public health to join with ACSH in communicating their concerns about Dr. Arnot s book. They can do this by contacting Andrew Lack, President of NBC News, and Little, Brown, and Co., publisher of The Breast Cancer Prevention Diet.

Summary of ACSH s Critique

ACSH concludes that Dr. Arnot s book The Breast Cancer Prevention Diet represents a disservice to women in the following ways:

  • it exploits women s deep seated fears of breast cancer;
  • it promises more than it can deliver;
  • following the book s advice could result in substantial disruption of eating patterns, both of women themselves and of their families (for example, Dr. Arnot recommends that women avoid rice, potatoes, and many forms of pasta);
  • not adhering to Dr. Arnot s dietary program could instill feelings of guilt;
  • it could discourage high risk women from seeking intensive medical monitoring (frequent mammograms, for example) and from accepting drug regimens (such as the recently approved tamoxifen) that have proven efficacious in reducing the toll of breast cancer, in favor of unproven dietary interventions;
  • it betrays the trust women have in physicians.

There are those who may object to ACSH s harsh criticism of Dr. Arnot s recommendations for preventing breast cancer by arguing:

  1. that it wouldn t hurt to give his diet a try;
  2. that it is unduly cautious not to act on preliminary, speculative data, and that it is imprudent to demand that all the scientific evidence be in before recommending that women take action to protect their health; and
  3. that giving women the hope of reducing their risk of breast cancer through following some dietary regimen (as opposed to not offering them any advice over and above the accepted screening guidelines) empowers women by allowing them to seize control of their health and their lives.

ACSH asserts, however, that all these arguments are specious. If, in this case, we were to tolerate these arguments by silent acquiescence such tacit acceptance would open the floodgates to a deluge of other unproven prevention strategies.

Regarding the first argument that it wouldn t hurt to give this diet a try as noted above, Dr. Arnot s diet could put a woman s health in jeopardy by encouraging her to confuse her health priorities.

With respect to the second argument that it is unduly cautious not to act on preliminary data and imprudent to demand that all the evidence be in ACSH notes that most of the breast cancer prevention strategies mentioned in Dr. Arnot s book do not approach the level of credible, documented scientific evidence. Were we in the public health profession to accept Dr. Arnot s mode of thinking that even hypotheses or the most preliminary animal data can form a legitimate basis on which to recommend interventions for the purpose of human disease prevention we would be condoning practitioners of all sorts peddling similarly unproven remedies to American consumers.

Finally, with regard to the third argument that giving women such a dietary regimen to follow somehow empowers them any argument that an unproven strategy without documented benefits could empower women is ultimately insulting and demeaning to women s intelligence.


NBC health correspondent Dr. Bob Arnot s book The Breast Cancer Prevention Diet: The Powerful Foods, Supplements, and Drugs That Can Save Your Life was published in October 1998(1). Dr. Arnot has publicized his book on television, most notably on Today and the Oprah Winfrey show. Information on the book has also been posted on the MSNBC website(2,3). Taking its cue from the 12 step programs used by Alcoholics Anonymous and other organizations, the book offers 12 steps and an array of diet plans designed both for women who wish to prevent breast cancer and for women already diagnosed with the disease.

Dr. Arnot has brought out his book at a time when American women s consciousness of and concern about breast cancer may be at an all time high. He taps into women s fears of the disease by mislabeling breast cancer an epidemic, and then goes on to appeal to his readers notions of feminism by asserting that by following his diet, women can grasp that sense of control and hope that this disease can be prevented and its intensity diminished.

Dr. Bob, as he is called, is a familiar and trusted friend to millions of television viewers. His position as chief medical correspondent for NBC News and the Today show gives him the sort of credibility and exposure that allow him to exert a powerful influence on the public. A 1997 study by the National Health Council found that 40% of American adults consider TV, more than any other outlet, their principal source of health information. The same study found that Americans trust the health information on TV news shows almost as much as the messages they get from their doctors.

The basic premise of Dr. Arnot s book is that certain foods inhibit or stimulate the development of breast cancer. Dr. Arnot does not blatantly state that his diet can cure breast cancer, but his argument strongly suggests that such a diet can treat and decrease the size of existing tumors. Adapting the sort of 12 step program first popularized by Alcoholics Anonymous, Dr. Arnot outlines 12 steps to prevent breast cancer. He goes on to offer prevention plans for women with high estrogen (before menopause), women with low estrogen (after menopause), survivors of breast cancer, and the daughters of survivors.

Dr. Arnot claims that by eating the right combination of foods, women can dramatically decrease their risk of breast cancer. Among his other prescriptions, Dr. Arnot recommends that women eat large doses of soy products and flaxseed for their estrogen blocking effects effects supposedly similar to those of tamoxifen and raloxifene, two drugs that currently are undergoing rigorous study for safety and efficacy for use in the prevention of breast cancer. According to The Breast Cancer Prevention Diet, the ultimate benefit of his diet is that foods can act as drugs and so can be used as a form of chemoprevention but without any of the drugs adverse side effects.

Although Dr. Arnot acknowledges several key organizations in the field of breast cancer early in his book, thereby subtly implying those organizations support for his conclusions, ACSH is unaware of any such endorsement. Indeed, in interviews with ACSH, some of the experts Dr. Arnot cites in his book (although none would comment on the record) have criticized The Breast Cancer Prevention Diet for misrepresenting their work.

The American Council on Science and Health (ACSH), a nonprofit consumer education and advocacy group, objects to The Breast Cancer Prevention Diet s imprudent and misleading claims. In this presentation, ACSH will refute many of the book s assertions and also offers women balanced and sound advice on understanding and reducing breast cancer risk.

Claims of The Breast Cancer Prevention Diet Versus Reality

1. Claim: There is an epidemic of breast cancer among American women.

Dr. Arnot s premise is that American women are in the midst of a breast cancer epidemic, and it may only get worse. To market Dr. Arnot s book, the MSNBC website plays on the fears of American women, using statements such as, This year, one in eight American women will be diagnosed with breast cancer.(2) In a later posting, the MSNBC site modifies this estimate to one in eight by age 85.(3) Dr. Arnot attempts to justify his claim by dismissing data from population cancer registries and leading cancer scientists. In place of the dismissed data he improvises his own definition of what constitutes an epidemic: . . . unacceptably high levels [of disease] by current world standards.


Breast cancer is the most common cancer in women in the United States, and reducing breast cancer rates is an important public health goal. While it is crucial that women be aware of their risk factors and recommendations for early detection, mislabeling the disease as an epidemic will not achieve this end. (An epidemic is a sudden, increased frequency of disease.) In contrast to the uncontrolled epidemic conditions portrayed by Dr. Arnot, among American women neither the age adjusted incidence nor the mortality rate for breast cancer has changed substantially in the past five years (see Figure 1).

Indeed, much of the increase in breast cancer incidence reported during the 1980s is attributable to the increased use of mammographic screening screening that detects the sort of early stage breast malignancies that previously were missed.(4) This progress in the war on cancer is reflected in the substantial increase in risk of early breast cancer cancer diagnosed in situ or in Stage I from 1983 to 1995, and in declines seen in mortality of late stage disease (see Figure 2).

The same advances in early detection that drove reported breast cancer incidence up during the 1980s are largely responsible for the declines in breast cancer mortality that have continued throughout the 90s.(4)

Dr. Arnot asserts that one in eight women will be diagnosed with breast cancer, yet he fails to provide the appropriate context. In actuality, this statistic refers to a woman s lifetime risk of breast cancer, and does not account for differences in other factors that affect breast cancer risk. The annual age adjusted risk of breast cancer in 1995 (the most recent year for which hard data are available) was 111.3 new cases per 100,000 American women, or approximately 1.1 new cases per 1,000 women.(5)

Throughout his book Dr. Arnot promotes the view that breast cancer is out of control. He uses such statements as, . . . despite the decades long, terrifying increase in new breast cancer cases, women have stood virtually powerless to prevent the disease. Such provocative language may serve to stir up interest in his book, but it does so at the cost of cultivating misunderstanding and unnecessary anxiety about breast cancer.

2. Claim: Differences in breast cancer rates between Asian and American women can be explained by diet.

According to Dr. Arnot, When Asian women move to the United States, they and their daughters suffer an increased risk of breast cancer close to that of American women. He goes on to attribute the low breast cancer risk measured for Asian women to their high intake of soy products.


A recent review of risk factors for breast cancer concluded that Differences in childhood nutrition patterns and energy balance seem to be reasonable explanations for much of the international differences in breast cancer risk, but require further exploration.(6)

Data from the California Cancer Registry show that in California, during 1995 and for each year since 1988, the age adjusted incidence of breast cancer among Asian and Pacific Islander women was approximately half that measured for all California women.(7) Some of the Asian women in California are immigrants from Asia, but many are women born in the United States who are the daughters, granddaughters, or great granddaughters of immigrants.

In truth, Asian women differ from their American counterparts not only in their dietary intake of soy but also in a number of important characteristics that predict risk of breast cancer. The leaner body mass, smaller size, and older age at menarche (8) measured for Asian women predict lower risk of breast cancer regardless of soy protein intake. To attribute differences in breast cancer rates between Asian and American women solely to the intake of dietary soy products is overly simplistic.

3. Claim: Foods can prevent breast cancer.

Dr. Arnot claims that the recent flood of medical studies confirms that what a woman eats can have a dramatic impact on whether or not she contracts [breast cancer].


The theory that nutrition plays an important role in breast cancer prevention is not new and has received extensive investigation in both animals and humans. Studies have identified protective relationships for a number of dietary factors when fed to rodents that had been chemically and genetically induced to develop breast cancer. Still, the relevance of such studies to humans remains unclear.

Higher intake of total calories and fat were once believed to be directly related to higher rates of breast cancer in humans. Recent investigations have shown, however, that these findings are more closely related to the presence of obesity. Obesity in post menopausal women is a known risk factor for breast cancer. In human studies, when the effects of obesity have been eliminated, most investigations have found little if any independent relationship between dietary factors and breast cancer risk. (9)

4. Claim: Soy and flaxseed are safer natural alternatives to chemoprevention, and they work by competing with estrogen for receptors on breast cells.

Dr. Arnot compares this preventive process to chemoprevention and proposes that women can block estrogen . . . with the right kinds of foods. He states, Flaxseed is...considered by the National Cancer Institute to be a designer food, that is, a food that has so many cancer fighting qualities it s as if it were tailor made as a medicine, not just a food.(p.60).


Some human studies of breast cancer have suggested that diets rich in phytoestrogens might have a protective effect, but this hypothesis is far from proven. Phytoestrogen rich foods include soybeans and soybean curd (tofu). Lignins are found in a number of foods, including soybeans, strawberries(10), and flaxseed.(10,11) Dr. Arnot s statement that intake of phytoestrogen rich foods can save your life represents a gross overstatement of current scientific evidence.

Several naturally occurring substances found in foods exhibit some weak estrogen like activity. Among these substances are isoflavone constituents of soybean products (diadzein and genistein) or other plant compounds (lignins), all of which bind to estrogen receptors in breast tissue and exhibit some estrogen activity. The weak estrogenic effects of these compounds collectively called phytoestrogens(12) together with their ability to bind with estrogen receptors in breast tissue, may allow them to block more active estrogen species from binding with the receptors.(13) The estrogen blocking effects proposed for phytoestrogens have been supported in some animal studies and in several investigations using human breast tissue grown in cell cultures. (14,15) The cancer reducing effects of phytoestrogens have received limited study in women, however.

As for the designer food claim, no such category exists at the N.C.I., nor was such a statement ever made, according to Dr. Caroline Clifford, Chief of Diet and Cancer (personal communication to Dr. Gilbert Ross).

5. Claim: Consumption of omega 3 fatty acids (found in fish oils) reduces risk of breast cancer.

In Dr. Arnot s words, The one quick step you can take to cut your risk of breast cancer is to consume omega 3 fatty acids every day. He recommends 10 grams of fish oil his preferred source of omega 3 fatty acids per day.


While certain attributes of omega 3 fatty acids may have important implications in human health, the benefits of omega 3 fatty acids in preventing breast cancer in humans has not been adequately studied.

In Part Two of his book, Dr. Arnot describes bleeding as an adverse affect of omega 3 fatty acid intake at very high doses. He recommends a dose of 10 grams per day more than two teaspoons for women at high risk of developing breast cancer. Aside from the difficulty of assessing one s personal risk for breast cancer without the aid of a health professional, 10 grams of fish oil per day seems excessive and may represent a dose sufficient to produce adverse effects in some women. This possibility is reinforced by Arnot s own statements that The British Nutrition Foundation recommends 1.25 grams per day as part of a healthy diet, and that it is difficult to get much more than 2 grams a day of fish oils in a normal diet.

The real hazards of ingesting so much fish oil may outweigh the speculative benefits, making this a particularly poor recommendation.

6. Claim: Women with high insulin levels are at higher risk for breast cancer.

Dr. Arnot argues that insulin acts as a growth factor for cancer development.


The relationship between insulin levels (or diabetes mellitus) and risk of breast cancer has received limited investigation in humans. In his book, Dr. Arnot attempts to link insulin levels with breast cancer risk. He makes the following assertion: Insulin is like half strength estrogen, stimulating cells to divide just like estrogen. However, the existence of a link between blood insulin levels and breast cancer is purely speculative. Until human studies are conducted and the findings evaluated, it is imprudent to presume that any association exists between either blood insulin levels or diabetes mellitus and breast cancer. In contrast to Dr. Arnot s assertion, diabetics have neither an elevated nor reduced incidence of breast cancer.

7. Claim: Low glucose intake protects against breast cancer by promoting weight loss.

Specifically, Dr. Arnot asserts, a low glucose load decreases insulin levels, hunger, and upper body fat. He goes on to suggest that a woman can lose weight by keeping her insulin levels low. Furthermore, he argues that by eating only foods with a low glycemic index, a person is more likely to lose weight.


People have high insulin levels typically because they are insulin resistant that is, their body cells are not normally responsive to insulin. This is, indeed, the case with many individuals with Type 2 diabetes. But this condition is not caused by the food one eats. It is usually caused by obesity, which in turn causes insulin resistance. Dr. Arnot s theory puts the cart before the horse, and ignores the basic truth that in order to lose body fat, one must consume fewer calories than one uses up whether those calories come from fat, from carbohydrate, or from protein.

Glycemic index per se has nothing to do with weight loss. Energy balance calories in versus calories out is the real key to weight loss. Furthermore, following Dr. Arnot s dietary prescription would involve omitting many healthful, nutrient rich foods from the diet foods such as orange juice, carrots, potatoes, yams, kiwi fruit, and green peas (to name just a few). Thus, Dr. Arnot s dietary prescription would decrease dietary variety and dietary variety is one of the hallmarks of a healthful diet.

8. Claim: Chemical estrogens such as pesticides in the environment act as super estrogens and increase risk of breast cancer.

Dr. Arnot suggests that synthetic chemicals called xenoestrogens a class that includes DDT, PCBs, and other organochlorines are possible risk factors for breast cancer. He describes xenoestrogens as super estrogens, chemicals in the environment [that] act just like an estrogen when they attach to the estrogen receptor on breast cells, but provide a signal that is many times more powerful. Although Dr. Arnot admits that scientific evidence does not support the argument that PCBs and DDT cause cancer, he introduces the theory that a mixture of pesticides creates a combination far more powerful than any estrogen. According to Dr. Arnot it is this synergistic effect an effect he claims is similar to that involved in Gulf War Syndrome that causes breast cancer.


Dr. Arnot s claim that xenoestrogens act as super estrogens is unsupported(16) and represents a major distortion of the far more important role played by the body s own estrogens. The estrogenic activity of DDT is minuscule in comparison to the activity of a woman s natural ovarian estrogens (estradiol, for example); and PCBs exhibit no estrogenic activity.(16) A recent assessment of cumulative exposure to xenoestrogens concluded that when compared to the effects of a woman s naturally occurring estrogens, the estrogenic effect of the xenoestrogens was minimal(16). Moreover, the original paper that showed a synergistic effect between compounds was withdrawn because its findings could not be replicated.(17,18)

Regarding the role pesticides might play in cancer, in 1990 the National Cancer Institute (NCI) issued a statement declaring that the NCI was unaware of evidence that suggests that regulated and approved pesticide residues in food contribute to the toll of human cancer in the U.S. (personal communication, NCI s Dr. Richard Adamson to ACSH President Dr. Elizabeth Whelan).

9. Claim: Alcohol is a risk factor for breast cancer.

Dr. Arnot states that Alcohol consumption is the most solidly established dietary factor related to cancer of the breast and one of the most powerful. He recommends abstaining from alcohol completely but also advises, if you do drink, organic products, such as champagne, wine, beer, tequila, and vodka are clearly the safest, since they have the least risk of contamination or carcinogens.


In spite of numerous investigations, the role played by alcohol intake in the development of breast cancer remains uncertain. While Dr. Arnot s position that alcohol use elevates risk of breast cancer is supported in some studies (19 23), no association is found in others (24 28).

If Dr. Arnot s statement were, in fact, true, women would be well advised to abstain from alcohol altogether. Until the reasons behind the discrepancies in the studies findings are resolved, however, it is not possible to arrive at definitive conclusions as to whether or not alcohol use plays a role in the development of breast cancer. Additionally, there are known health benefits to the consumption of moderate amounts of alcohol.

Dr. Arnot s advice to drink organic alcohol products to reduce the risk of contamination or carcinogens is completely unfounded. Organic products do not protect against microbial contamination; on the contrary, they may increase one s risk of food borne illness. Furthermore, his suggestion that pesticide residues from non organic products are carcinogenic is scientifically unsupported. Dr. Arnot is perpetuating misconceptions.

10. Claim: Increased vitamin D intake decreases the risk of breast cancer.

Dr. Arnot writes, Vitamin D is a potent inhibitor of a cell s ability to divide and grow. Vitamin D also helps breast cells to become more mature so they are less vulnerable to cancer causing toxins.


Studies have not shown Vitamin D to have a preventive effect on breast cancer. In fact, Dr. Arnot makes this point himself: There is no evidence that a vitamin D supplement has any effect on breast cancer rates. Despite the lack of any proof, however, Arnot goes on to recommend eating a minimum of 200 IU of vitamin D a day for breast cancer prevention. The latest Recommended Daily Allowance (RDA) for vitamin D for women over age 50 is 400 IU, while for those over 70, the RDA is 600 IU. Women in these age groups who follow Dr. Arnot s diet may not receive sufficient amounts of vitamin D. Furthermore, Dr. Arnot fails to note that excess vitamin D is toxic.

11. Claim: Foods are drugs without the side effects.

Dr. Arnot writes, Drugs strongly interfere at one very specific point in the sequence that causes cancer, and can therefore develop prominent side effects. By changing your diet, you can interrupt many places in the sequence without the toxicity of drugs.


The pharmaceuticals tamoxifen and raloxifene have anti estrogen functions similar to those described for phytoestrogens. A clinical trial designed to assess the safety and effectiveness of tamoxifen at reducing risk of breast cancer among high risk women identified a 49 percent reduction in incidence among women using the medication, when compared to a group receiving a placebo.(29)

In contrast with the breast cancer benefits, however, risk of endometrial cancer was more than doubled among the women receiving tamoxifen, when compared to the women assigned the placebo. Additionally, the incidence of stroke, pulmonary embolism, and deep vein thrombosis was elevated among the women receiving tamoxifen, relative to the same outcomes in the placebo group.

Raloxifene may prove to be as protective as tamoxifen against breast cancer, but with fewer side effects. These drugs are still being studied in large scale clinical trials, however. There is a great potential benefit for tamoxifen and raloxifene, but this benefit must be balanced against the increased risk of other serious problems.

Similar consideration of risks and benefits would be advisable for phytoestrogens. Dr. Arnot s characterization of the potential benefits of soy protein as similar to those of tamoxifen without the side effects has not been established and should not be assumed until soy protein undergoes the scrutiny of analytic study in humans, by means of tests similar to those conducted for tamoxifen. The fact that soy protein is a food does not dismiss the possibility of adverse effects resulting from its indiscriminate use.

If Dr. Arnot believes that the anti estrogenic activity of soy protein is similar to that exhibited for tamoxifen, it seems imprudent of him to recommend unchecked use of phytoestrogen rich foods without considering the possibility of adverse outcomes comparable to those identified for tamoxifen. Similar arguments can be made for raloxifene and for high dose intake of omega 3 fatty acids.

Furthermore, Dr. Arnot s suggestion that these food substances as contrasted with pharmaceuticals, which are subject to the most stringent government efficacy and safety testing have the same level of beneficial effects is misguided.

The You Cannot Err With The Breast Cancer Prevention Diet Philosophy

When counseling health practitioners about the dangers of using dubious remedies, medical sages down the ages have warned, primum non nocere: first, do no harm. Dr. Arnot maintains that you cannot err with a healthy diet. But by making unfounded life saving claims, The Breast Cancer Prevention Diet, is offering something other than a healthy diet. Trusting Dr. Arnot s version of science and adhering to his diet could cause real harm.

  • Dr. Arnot s message that his diet allows women to take control of their breast cancer risk, and his claim that his diet offers effects comparable to those of drugs without the side effects, may confuse women and cause them to neglect well established recommendations such as the standard recommendations for routine physician evaluations and mammography for early, potentially life saving breast cancer detection.
  • Dr. Arnot s suggestion that following his diet may shrink breast tumors may influence women who feel a lump to attempt to treat themselves with this diet rather than seeking reliable medical evaluation. There is no evidence in the medical literature that following this diet will shrink human breast tumors.
  • Dr. Arnot s message may lead women suffering from breast cancer to feel personally responsible for their condition to feel guilty because they did not follow Arnot s diet (If only I had eaten the right foods, I wouldn t be ill.). Arnot downplays the role of genetics and unknown factors in the development of breast cancer. (Indeed, most breast cancers are sporadic and not secondary to known risk factors.)
  • The diet plans Dr. Arnot recommends with little or no scientific foundation require major lifestyle changes changes that could disrupt already healthy eating habits for the entire family, especially children.
  • Dr. Arnot s book is alarmist. It promotes exaggerated perceptions of risk, and undermines confidence in well established scientific methods for breast cancer prevention and study. These methods include: regular mammography screening for women over age 40, regular Breast Self Examination, avoidance of obesity, regular exercise and regular medical check ups.

Known Risk Factors for Breast Cancer

A number of risk factors for breast cancer have been scientifically established. They include:

  • age over 50;
  • genetic factors/family history (first degree relatives mother, sisters, daughters);
  • prior history of breast cancer;
  • history of benign breast disease;
  • early menarche (before age 12);
  • late menopause (after age 50);
  • later age at first full term pregnancy (after age 35);
  • postmenopausal estrogen replacement therapy;
  • postmenopausal obesity;
  • low physical activity;
  • high dose exposure to ionizing radiation early in life.

Executive Summary and Conclusion

The scientists of the American Council on Science and Health and other leading health professionals many of them scientists whose work is referred to in Dr. Bob Arnot s The Breast Cancer Prevention Diet are gravely disturbed by the irresponsible and unfounded claims propagated in this book. In an effort to offer a sounder and more balanced viewpoint, ACSH has issued this peer reviewed report refuting the arguments set forth in Dr. Arnot s book.

One advertisement for Dr. Arnot s book describes it as a runaway best seller and urges women: Don t wait to save your life. That urgent plea may sound extreme just another example of advertising hyperbole but, in fact, Dr. Arnot does claim that his diet offers a life saving effect to women at risk for breast cancer (meaning, of course, all women).

Dr. Arnot bases his diet on laboratory work done with animals and on preliminary human studies. In so doing, Dr. Arnot endorses imprudent approaches to preliminary findings and advocates abandoning the time tested methods of scientific inquiry. He also undermines women s trust in established, well founded methods for breast cancer screening and risk reduction. Regardless of the potential of diet as a preventive measure against breast cancer, the benefits suggested so far cannot be extrapolated to humans without further research.

Many of the dietary interventions for breast cancer prescribed by Dr. Arnot do, indeed, represent scientific hypotheses that are worthy of further study. Potential benefits for some of the nutritional recommendations made in The Breast Cancer Prevention Diet appear promising, although none have undergone the scrutiny and testing required to conclude that their use can save your life.

A significant body of health and medical experts join with ACSH in criticizing The Breast Cancer Prevention Diet. Many of these scientists have expressed concern and outrage, both at Dr. Arnot s misrepresentation of scientific data, and at the potential effect that that misrepresentation could have on women s trust in established preventive measures, and confidence in the scientific legitimacy of physicians advice in general. While there is indeed much misinformation on health to be found in bookstores, the internet, and TV, this book is particularly disturbing because Dr. Arnot, as NBC s chief medical correspondent, is family doctor to millions of viewers.


Misrepresenting Science
Selected Examples from The Breast Cancer Prevention Diet
Dropping Names

The Breast Cancer Prevention Diet opens with a section acknowledging numerous recognized research institutions, scientists and medical experts. Through his acknowledgments, Dr. Arnot implies that the individuals and institutions named are endorsing his recommendations. As a means of legitimizing the book by these associations, the text is riddled with the names of respected scientists and physicians. Yet, when the American Council on Science and Health contacted many of the scientists cited, most were unaware of The Breast Cancer Prevention Diet, and not one endorsed the book. He appropriated the aura of the National Cancer Institute with an outlandish statement: he claimed that the N.C.I. called flaxseed a designer food, a category he apparently contrived for his book.

Quoting Out of Context

In another attempt to justify some of the book s assertions, Dr. Arnot often juxtaposes his claims with unrelated quotes from medical professionals or scientists. In Part Two of the book, the chapter on increasing fiber begins with: Fiber may be the most underrated of all breast cancer preventive nutrients. Yet at major cancer centers such as Memorial Sloan Kettering, it is finally getting its due. Moishe Shike, director of clinical nutrition, says Absolutely, I think fiber is so important (p. 113). Dr. Arnot leads the reader to believe that Dr. Shike is stressing the importance of fiber in preventing breast cancer. Yet Dr. Shike is quite possibly referring to fiber only as an important component to a healthy diet.

Citing Statistics Without Reference

Throughout the text, Dr. Arnot often gives specific statistics without providing a reference. A few prime examples are: The great good news is that researchers have observed a 40 percent decrease in breast cancer for women who eat a diet rich in vegetables, even before fruit is added to the diet (p. 123 41; Cruciferous vegetables decreased the risk by 40 percent in a Wisconsin study (p.92); Four drinks a day and your risk increases by 44 percent (p.36); In humans omega 6 fats account for a stunning 69 percent increased risk of breast cancer (p.42). Without specific references, readers are encouraged to blindly accept some incredible claims Dr. Arnot offers in his book.

Mis reporting Research

Many of the components of The Breast Cancer Prevention Diet are premature adaptations from animal laboratory studies or preliminary human studies. In his book, Dr. Arnot routinely misleads readers by implying that the studies cited have included humans (specifically women) as their subject pool, and breast cancer risk as their final outcome measure. Some of Dr. Arnot s interpretations of scientific studies are distorted to support his diet. He confuses readers who may not have the scientific background nor resources available to objectively evaluate his conclusions.

For example, in the same chapter referenced above on increasing fiber, Dr. Arnot states that there is little wonder why fiber is such a powerful preventive agent. Fiber interrupts most steps of the estrogen pathway to decrease the blood level of an estrogen called estrone sulfate by a powerful 36 percent. That translates into a 54 percent decrease in cancer risk for women on a high fiber diet (p.113).

Dr. Arnot then refers to a June 1997 study in Nutrition that examined the effects of wheat bran supplementation on the major serum estrogens during the phases of the menstrual cycle. While the study did find significant decreases in some estrogen types, a clear dose response effect was not established. More importantly, risk of breast cancer was not used an outcome measure. Therefore, the conclusion that women on a high fiber diet have a decreased risk of breast cancer cannot be drawn from this study. It is also unclear how Dr. Arnot arrived at the percentage decrease noted of 54% in cancer risk for women on a high fiber diet.

An especially dangerous example of reporting research out of context is found in the book s reference to the work of Dr. Lilian Thompson. Dr. Arnot writes: what she has found is that breast cancer size actually decreased with a daily course of flaxseed (p. 7; similar reference on p. 42, and p. 60 61). At least two studies of Dr. Thompson have found flaxseed supplementation to reduce the size of mammary tumors, yet these studies were performed on rats, not on women (Nutr Cancer 1996;26(2):159 65 and Carcinogenesis, 1996 Jun;17(6):1373 6). Dr. Thompson told us she is only now beginning to evaluate human subjects.

This distinction is most important. In rodent studies, cancer is commonly induced by the injection or smearing of a carcinogen. Humans do not develop cancer in this manner; human physiology is not equivalent to that of rodents. While animal studies provide valuable information and a basis for further research, one must recognize their limitations and not simply extrapolate their results to man. Women who learn of these rodent studies, unaware of their preliminary nature, may well be tempted to treat a breast lump with flaxseed, rather than seek earlier, possibly life saving medical intervention.


1. Arnot, RA. The Breast Cancer Prevention Diet: The Powerful Foods, Supplements, and Drugs That Can Save Your Life. New York: Little, Brown, and Company, 1998.

2. Arnot, RA. MSNBC web site 10/1/98

3. Arnot, RA. MSNBC web site 10/5/98

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