Last Updated: 12/2/2007

The information in this column is intended for informational purposes only, and does not constitute medical advice or recommendations by the author.  Please consult with your physician before making any lifestyle or medication changes, or if you have any other concerns regarding your health.

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OBESITY & RISK OF CANCER

There is growing evidence that the risk of at least some cancers is increased by obesity.  At a time when more than two-thirds of Americans are considered overweight or obese, this is an area of obvious public health concern.  An interesting large-scale public health study from England, just published in the British Medical Journal, adds further evidence of a link between obesity and an increased risk of developing cancer.

The United Kingdom (UK) Million Women Study enrolled 1.2 million women, ages 50 to 64, into the study between 1996 and 2001.  This very large study population of women has, on average, been closely observed for more than 5 years now.  The incidence of 17 different cancers was tracked in this large group of women, and the relationship between BMI (body mass index) and the incidence of these 17 cancers was carefully studied.  Potential confounding factors, other than body weight, were also included in the analysis of the data, including age, region of residence, socioeconomic status, age at the delivery of each woman’s first child and number of pregnancies (known risk factors for breast cancer), smoking history, alcohol intake, level of physical activity, and menopausal status and hormone replacement therapy history (additional known risk factors for breast cancer). 

During the study period, there were 45,037 cancers diagnosed among these 1.2 million women, and 17,203 deaths due to cancer.  Significantly, the study found that 10 of the 17 cancers evaluated were increasingly more common as body weight increased.  Specifically, cancers of the uterus, esophagus, kidney, pancreas, ovaries, breast, colon, and rectum occurred more commonly as body weight increased, as well as leukemia, multiple myeloma, and lymphoma.  Based upon the results obtained in this very large study, the authors estimate that as many as 5% of all cancers diagnosed in the UK can be attributed to being overweight or obese, alone. 

This is a very compelling study, as it reinforces data from previous studies that have shown a linkage between obesity and the risk of certain cancers.  Studies such as this one are also extremely important, because obesity is a risk factor that is largely preventable through lifestyle changes.  Much as 95% of new lung cancer cases (the #1 cancer killer in the developed world) could be prevented if smoking was eliminated overnight, this particular study suggests that 5% of all cancers observed in British women could have been prevented if excessive body weight had been eliminated from this population. 

Certainly, not all risk factors for cancer can be eliminated altogether.  However, readily modifiable risk factors, including obesity, decreased physical activity, smoking, and excessive alcohol intake, are risk factors that we all have control over.  Eat healthy, exercise frequently (even relatively moderate exercise, 4 to 5 times per week, has been shown to significantly cut down on the risk of cardiovascular disease and cancer), don’t smoke, and don’t drink more than 1 or 2 alcoholic beverages per day.  There is ample research data to suggest that you can significantly reduce your risk of developing the diseases that account for the majority of preventable deaths in our society by adopting these lifestyle modifications.

A second study, from Sweden, looks at dietary fat content and the risk of breast cancer in a population of over 49,000 premenopausal women who volunteered to participate in this lifestyle and health study.  This study, recently published in the British Journal of Cancer, specifically evaluated not only total fat intake, but also the type of dietary fats consumed by the study participants, and assessed the risk of developing breast cancer based upon this dietary information.

Interestingly, overall dietary fat intake did not seem to be associated with breast cancer risk.  However, the women who consumed the largest amounts of the so-called “healthy fats” (monounsaturated and polyunsaturated vegetable-based fats) had a significantly lower incidence of breast cancer when compared to women who consumed the least amount of these healthier fats and oils.  Indeed, there was a 50% reduction in the risk of developing breast cancer observed among the group of women with the highest dietary intake of monounsaturated and polyunsaturated fats.  A diet low in saturated fats (i.e., animal-based fats) is known to improve cardiovascular health, and according to the findings of this public health study, may also lower one’s risk of developing breast cancer.


TESTOSTERONE LEVELS & MORTALITY RISK

A new study from the UK, just published in the journal Circulation, prospectively studied approximately 2,300 men (ages 40 to 79) who had participated in a much larger study that involved almost 12,000 men.  All of the men in this study had testosterone levels measured in their blood when they first enrolled in this research study.  In this study, unlike reports from some other clinical studies, higher levels of testosterone were actually associated with a lower risk of death from all causes, and specifically for death due to cardiovascular disease and cancer.

Despite all of the favorable attributes of testosterone, there have been a number of studies that have linked high levels of testosterone, in men, with an increased risk of death due to cardiovascular disease and certain cancers.  At the same time, other studies have suggested that high testosterone levels may actually protect men from certain causes of premature death.

Before any readers run to their physicians to try and arrange for testosterone injections, it must be said that this study’s finding of an inverse correlation between serum testosterone levels and risk of death due to heart disease and cancer does not actually prove that a higher level of testosterone is, by itself, directly responsible for the decreased death rates observed in this study.  There are many factors that affect testosterone levels in men, including age, weight status, smoking, diabetes, alcohol intake, and level of physical activity.   While the authors of this study attempted to correct for observed differences in these factors among the men participating in this clinical study, their data still does not prove that one can actually reduce one’s risk of death by taking testosterone supplements (and testosterone supplements are not without known potential side effects, either).  Testosterone may indeed be responsible for the favorable health findings identified in this study of men, or serum testosterone may simply be a surrogate for some other health factor (or factors) that may, instead, be responsible.

RESEARCHER FINANCIAL TIES & RESEARCH FINDINGS

In recent years, there has been growing concern among medical ethicists and medical journal editors about the rising influence of drug companies who finance clinical research directed at their pharmaceutical products.  Increasingly, as government-sponsored research grants become smaller and more competitive, clinical researchers are finding that many drug companies are all too happy to step into this growing research funding void and provide support to research scientists and clinicians.  Likewise, there have been multiple studies that have shown, conclusively, that clinical lectures, dinners, parties and even token gifts, when sponsored by drug companies, result in significant shifts in physician prescribing habits in favor of the sponsoring drug companies’ products.

A new study in the British Medical Journal analyzed 124 previously published studies that evaluated medications used to treat high blood pressure.  All of these 124 studies were, themselves, research studies that collectively analyzed large numbers of previously published research to try and determine which high blood pressure drugs were likely to be the most effective (these types of studies are referred to as meta-analyses, and they have their own potential weaknesses and biases as well).  Of these 124 meta-analysis studies, a whopping 40% were supported by the drug company that manufactured and sold the medication being studied.

Interestingly, the actual data presented in these 124 studies did not appear to be more favorable among those studies that were supported by the manufacturers of the medications being evaluated.  However, tellingly, those studies that were financially supported by drug companies were more than 5 times more likely to draw favorable conclusions and recommendations, by the studies’ authors, about the medications being studied. 

The results of this study are not terribly surprising, but they are quite sobering in light of the enormous costs of prescription medications in most countries, and particularly those medications that are still covered by their manufacturers’ patents, and are often no more effective than much cheaper generic medications used to treat the same medical conditions. 

SMOKING & THE RISK OF COLON & RECTAL CANCER

There is some research data to suggest that smoking increases the risk of developing colorectal cancer, but there is also other data suggesting little, if any, increased association between tobacco and cancers of the colon and rectum.  A new study in the Journal of the National Cancer Institute strongly suggests that smoking may indeed increase the risk of rectal cancer after all.  The data for these conclusions actually comes from the landmark Women’s Health Initiative (WHI) study, which showed, conclusively, 5 years ago, that prolonged hormone replacement therapy increased women’s risk of developing breast cancer and heart disease.  Indeed, this huge prospective study may actually have contributed to the unprecedented recent decline in the annual incidence of breast cancer observed in the United States, as a result of the marked decrease in the number of prescriptions written for hormone replacement therapy medications since the WHI study was published (and the subject of a forthcoming book that I am currently writing I might add).

The nearly 147,000 women participating in the WHI study were assessed for a history of active or passive smoking, and for the incidence of colon and rectal cancer, during nearly 8 years of follow-up.  The resulting and very robust data indicated that women who were actively smoking while enrolled in the study had nearly twice the risk of developing rectal cancer when compared to non-smokers, even after other risk factors for rectal cancer were controlled for in the analysis of the data.  Quite unexpectedly, active smoking did not appear to be associated with an increased risk of colon cancer, however (why this is so remains unclear and unexplained, thus far).  

Finally, chronic exposure to secondhand smoke, which is a known risk factor for lung cancer, emphysema, and cardiovascular disease, was not associated with an increased risk of cancers of the colon or rectum.  Needless to say, there is more than 50 years of data confirming the serious, life-threatening effects of smoking, and abundant clinical research is quite clear that there is really no safe level of exposure to tobacco smoke, whether you are actively smoking or you happen to be passively exposed to someone else’s tobacco smoke.

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Disclaimer:  As always, my advice to readers is to seek the advice of your physician before making any significant changes 
in medications, diet, or level of physical activity.

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Dr. Robert Wascher is an oncologic surgeon, professor of surgery, and a widely published author. 

Dr. Wascher is the Director of the Division of Surgical Oncology at Newark Beth Israel Medical Center. 

Send your feedback to Dr. Wascher at rwascher@doctorwascher.net
 

http://www.sbhcs.com/hospitals/newark_beth_israel/mservices/oncology/surgical.html