Soy (Isoflavones), Osteoporosis, and the Symptoms of Menopause


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A new placebo-controlled, double-blinded research study showed no benefit from soy supplements in reducing osteoporosis or the symptoms of menopause.



SOY (ISOFLAVONES), OSTEOPOROSIS, AND THE SYMPTOMS OF MENOPAUSE

As I discuss in detail in my recent book, A Cancer Prevention Guide for the Human Race, combination hormone replacement therapy (HRT) for the symptoms of menopause have been clearly linked to an increased risk of breast cancer.  (This important topic is also the subject of my next book, which will be published in 2012.)  Since the preliminary findings of the landmark Women’s Health Initiative study were released in 2002, proving the link between HRT and breast cancer, many women and their physicians have been searching for safer alternatives to HRT in an effort to relieve the symptoms of menopause, and to reduce the risk of thinning of the bones (osteoporosis).

There have been several public health research studies that have suggested a role for soy foods in the prevention of both osteoporosis (“thin bones”) and menopausal symptoms. Indeed, the findings of these studies make scientific sense, as soy isoflavones, which are present in many soy food products (and especially in tofu), act as a weak form of estrogen. (It is the loss of estrogen production in the ovaries, after menopause, that leads to both osteoporosis and the unpleasant symptoms of menopause in postmenopausal women.) However, as with the vast majority of disease prevention research in general, the available research data linking soy isoflavones to improvements in bone density and menopausal symptoms has been in the form of survey-based studies, and other relatively unreliable types of research studies. Now, a newly published prospective, randomized, placebo-controlled, doubled-blinded clinical research study takes a closer (and more accurate) look at the impact of soy isoflavone supplements on osteoporosis and menopausal symptoms. This clinical research study appears in the current issue of the Archives of Internal Medicine.

In this study, 122 postmenopausal women were randomized to receive a daily soy isoflavone supplement pill (200 mg), while 126 postmenopausal women were randomized to receive a placebo (sugar) pill that was identical in appearance to the soy isoflavone pills. Neither the research study volunteers nor the research staff knew which patient volunteers received the soy isoflavone tablets and which volunteers received the placebo pills until the research study was completed. These patient volunteers were all followed for an average of 2 years. Bone density measurements were performed at the beginning of the study, and then again 2 years later. Common menopausal symptoms were also tracked throughout the duration of this study.

After 2 years of observation, there was no significant difference in bone density measurements between the two groups of women who participated in this clinical research study (in both groups of women, there was an average bone density loss of about 2 percent over the 2-year period of this study). Moreover, the women in the soy isoflavone group actually reported ahigher incidence of hot flashes and constipation than the women in the placebo group.

In this well-controlled prospective, randomized, doubled-blinded, placebo-controlled clinical research study, a daily supplement of 200 mg of soy isoflavones neither improved postmenopausal bone density loss nor improved the most troublesome symptoms of menopause.  (Whether or not higher doses of soy isoflavones, or natural soy foods instead of soy isoflavone supplements, might have shown some beneficial effect on bone density loss or menopausal symptoms in postmenopausal women cannot be answered by this study.)  Therefore, this study convincingly shows that even relatively large daily doses of purified soy isoflavones have no beneficial effect on either bone density loss or menopausal symptoms in postmenopausal women.  Based upon the results of this study, if you are currently taking soy isoflavone supplements in an effort to reduce your risk of osteoporosis, or the symptoms of menopause, this high-level clinical research study indicates that you are probably wasting your time and money on such supplements.  (However, as I discuss in A Cancer Prevention Guide for the Human Race, soy foods may actually reduce a woman’s lifetime risk of developing breast cancer, particularly if consumed during early adolescence and early adulthood, and soy products may also decrease a man’s lifetime risk of developing prostate cancer.)

 

For a comprehensive guide to living an evidence-based cancer prevention lifestyle, order your copy of my new book, A Cancer Prevention Guide for the Human Race.  For the price of a cheeseburger, fries, and a shake, you can purchase this landmark new book, in both paperback and e-book formats, and begin living an evidence-based cancer prevention lifestyle today!

For a groundbreaking overview of cancer risks, and evidence-based strategies to reduce your risk of developing cancer, order your copy of my new book, A Cancer Prevention Guide for the Human Race,” from Amazon, Barnes & Noble, Books-A-Million,Vroman’s Bookstore, and other fine bookstores!

On Thanksgiving Day, 2010, A Cancer Prevention Guide for the Human Race was ranked #6 among all cancer-related books on the Amazon.com “Top 100 Bestseller’s List” for Kindle e-books! On Christmas Day, 2010, A Cancer Prevention Guide for the Human Race was the #1 book on the Amazon.comTop 100 New Book Releases in Cancer” list!


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



Dr. Wascher is an oncologic surgeon, professor of surgery, cancer researcher, oncology consultant, and a widely published author



For a different perspective on Dr. Wascher, please click on the following YouTube link:

Texas Blues Jam



I and the staff of Weekly Health Update would again like to take this opportunity to thank the more than 100,000 health-conscious people, from around the world, who visit this premier global health information website every month. (More than 1.2 million health-conscious people visited Weekly Health Update in 2010!) As always, we enjoy receiving your stimulating feedback and questions, and I will continue to try and personally answer as many of your inquiries as I possibly can.





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Soy, Curcumin & Prostate Cancer Risk

 

Welcome to Weekly Health Update


“A critical weekly review of important new research findings for health-conscious readers”



SOY, CURCUMIN & PROSTATE CANCER RISK

Because chronic inflammation within the prostate gland is through to be an important risk factor for prostate cancer, anti-inflammatory dietary supplements and medications may be able to reduce the risk of prostate cancer by reducing inflammation.

Isoflavones from soy-based foods are known to act as a weak form of estrogen (the dominant female sex hormone).  Based upon this estrogen-like behavior, as well as potential anti-inflammatory properties, soy isoflavones are being studied as possible prevention and treatment agents for prostate cancer, and other types of cancer. 

Curcumin, which is present in the Indian curry spice turmeric, is also known to have potent anti-inflammatory properties, and has also been the subject of considerable cancer prevention and cancer treatment research.

A newly published prospective, randomized, blinded, placebo-controlled research study, published in the current issue of the journal Prostate, suggests that the combination of soy isoflavones and curcumin may have important potential prostate cancer prevention properties.

In the first part of this study, human prostate cancer cells were treated with a combination of soy isoflavones and curcumin.  Treatment of these human cancer cells with soy isoflavones and curcumin resulted in a significant reduction of prostate-specific antigen (PSA) production by these malignant cells (PSA is a marker of both prostate gland inflammation and prostate gland cancer).

As regular readers of this column are already aware, treatments performed in the laboratory that have beneficial effects on cancer cells, or on mice or rats, do not always have the same positive effects on living, breathing human beings.  Therefore, the findings of the second part of this study are of particular interest.  A total of 85 men with elevated PSA levels, but without prostate cancer (as confirmed by prostate biopsy), were enrolled in the second phase of this intriguing small study.  These 85 men were divided into two groups, and one group received daily supplements containing both soy isoflavones and curcumin, while the second (control) group of men received placebo (sugar) pills that were identical in appearance to the supplement pills (neither the 85 men, nor the nurses who dispensed the supplement pills and placebo pills, were aware of which pills each study volunteer was receiving until after the research study had been completed).

PSA blood levels were tested at the beginning of the clinical portion of this study, and once again 6 months later.  As was observed in the prostate cancer cells during the first part of this study, men with a PSA level of 10, or higher, experienced a significant reduction in their blood PSA levels 6 months after starting daily supplementation with soy isoflavones and curcumin.

Although this brief study cannot definitively confirm that soy isoflavone and curcumin supplements reduce the risk of prostate cancer, their ability to reduce elevated PSA levels in men with chronic prostate inflammation, but without evidence of prostate cancer, at least suggests a potential role in the prevention of prostate cancer (presumably through a reduction in prostate gland inflammation).

While there are multiple human research studies underway that are evaluating the effectiveness of soy isoflavones as cancer prevention agents, currently, there are no major human studies looking at the effects of curcumin on prostate cancer risk.  Based upon the findings of this small, interesting study of soy isoflavones and curcumin, which suggest a potential additive effect on PSA reduction when both of these dietary supplements are taken together, human research trials should be developed to look at the long-term impact, if any, of combined soy isoflavone and curcumin supplementation on prostate cancer risk.

 

For additional research information on soy isoflavones and curcumin in cancer prevention and cancer treatment, please review the following previous columns:

Soy Foods & Stomach Cancer Risk

Cruciferous Vegetables, Soy & Breast Cancer Risk

Soy Isoflavones & Recurrent Prostate Cancer

Soy Isoflavones Decrease Breast Cancer Recurrence Risk

Genistein (Soy Isoflavone) & Prostate Cancer

Diet, Soy & Breast Cancer Risk

Viagra & Sexual Function in Women; Patient-Reported Adverse Hospital Events; Curcumin & Pancreatic Cancer



To learn more about the role of soy isoflavones and curcumin in the prevention of cancer, look for the publication of my new landmark book, “A Cancer Prevention Guide for the Human Race,” in the summer of this year.  


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


Dr. Wascher is an oncologic surgeon, a professor of surgery, a cancer researcher, an oncology consultant, and a widely published author  


For a different perspective on Dr. Wascher, please click on the following YouTube link: 


http://www.youtube.com/watch?v=7-Tdv7XW0qg



I and the staff of Weekly Health Update would like to take this opportunity to thank the more than 100,000 new and returning readers who visit our premier global health information website every month.  As always, we enjoy receiving your stimulating feedback and questions, and I will continue to try and personally answer as many of your inquiries as I possibly can.



 

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Soy & Curcumin Reduce Prostate-Specific Antigen (PSA)

May 23, 2010 by Robert Wascher  
Filed under Weekly Health Update

 

Welcome to Weekly Health Update



“A critical weekly review of important new research findings for health-conscious readers” 

SOY & CURCUMIN REDUCE PROSTATE-SPECIFIC ANTIGEN (PSA)

Regular readers of this column are already aware that the regular consumption of foods containing soy isoflavones may be associated with a reduced risk of developing prostate cancer, and other types of cancer as well.  Curcumin, as curry lovers know, is contained within the spice known as turmeric.  Curcumin has been extensively studied, and it too may possess anti-cancer properties as well.  Both of these dietary compounds are thought to have potent anti-inflammatory effects on the prostate gland, and on other organs of the body.  Additionally, soy isoflavones also act weak estrogens (“phytoestrogens”), and may suppress prostate gland activity on this basis too.

Prostate cancers, as well as the normal prostate gland cells that give rise to prostate cancer, produce PSA (prostate-specific antigen), which allows doctors to detect new or recurrent prostate cancers by measuring the level of PSA in the blood.  A newly published research study, which appears in the current issue of the journal The Prostate, adds further evidence that soy isoflavones and curcumin may have an important role to play in prostate cancer prevention and, possibly, prostate cancer treatment.

This study consisted of both a laboratory experiment and a small clinical research trial with human volunteers.  In the laboratory portion of this study, human prostate cancer cells were treated with soy isoflavones and curcumin.  When these prostate cancer cells were treated with soy isoflavones and curcumin, the production of PSA by these cells was dramatically decreased.  Moreover, a receptor for male sex hormones, which prostate cancers use to fuel their growth, was significantly suppressed following treatment of these cells with soy isoflavones and curcumin.

In the clinical portion of this research study, men who had undergone prostate gland biopsies due to an elevated PSA blood level, but who were subsequently found not to have prostate cancer, were also evaluated.  In this prospective, randomized, placebo-controlled trial, 85 men without prostate cancer, but with elevated blood PSA levels, were divided into two groups.  The “experimental group” of men received curcumin and soy isoflavones once per day.  The “control group” of men received a placebo (“sugar pill”) once per day.  Neither group of male volunteers, nor the research assistants who dispensed these pills, knew which men received the placebo pills and which received the soy isoflavone and curcumin pills.

PSA levels were tested in all of these male volunteers at the beginning of the study, and 6 months later.  Among the men randomized to receive daily supplements of soy isoflavones and curcumin, the level of PSA in their blood dramatically declined following 6 months of supplementation with soy isoflavones and curcumin. 

While the results of this small and elegant research study do not prove that soy isoflavones and curcumin can actually prevent prostate cancer in humans, these results do suggest, at least, a biological mechanism whereby these dietary compounds might reduce the risk of developing prostate cancer, and might also have anti-cancer effects in patients with prostate cancer.  However, only large-sale prospective, randomized, blinded, placebo-controlled human clinical trials will be able to prove that these dietary compounds can actually prevent or effectively treat prostate cancer.

At this time, there are multiple ongoing and recently completed prostate cancer prevention and treatment clinical research trials using soy isoflavone supplements.  The results of several of these studies will, hopefully, become available within the next 3 to 5 years. 

While there are multiple cancer prevention and cancer treatment research trials underway that are evaluating curcumin, none of these ongoing curcumin clinical trials are focused on prostate cancer, unfortunately. 

Based upon the findings of this small and innovative research study of soy isoflavones and curcumin, the next logical step would be a large prospective, randomized, placebo-controlled, blinded study that randomizes patient volunteers to placebo, versus soy isoflavones only, versus curcumin only, versus a combination of soy isoflavones and curcumin.  A cancer prevention study could look at prostate cancer incidence in men who are already at high risk of developing this common form of cancer.  A prostate cancer treatment study, using the same methods, could assess the clinical impact of soy isoflavones and curcumin on the progression or recurrence of prostate cancer in men who have already been diagnosed with this form of cancer.

 

To learn more about the role of soy isoflavones and curcumin as potential cancer prevention nutrients, look for the publication of my new landmark evidence-based book, “A Cancer Prevention Guide for the Human Race,” in the summer of this year.



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


Dr. Wascher is an oncologic surgeon, a professor of surgery, a cancer researcher, an oncology consultant, and a widely published author



For a different perspective on Dr. Wascher, please click on the following YouTube link: 

http://www.youtube.com/watch?v=7-Tdv7XW0qg



I and the staff of Weekly Health Update would like to take this opportunity to thank the nearly 120,000 new and returning readers who visited our premier global health information website last month.  As always, we enjoy receiving your stimulating feedback and questions, and I will continue to try and personally answer as many of your inquiries as I possibly can. 


 

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Soy Foods & Stomach Cancer Risk

May 9, 2010 by Robert Wascher  
Filed under Weekly Health Update

 

Welcome to Weekly Health Update



“A critical weekly review of important new research findings for health-conscious readers” 

SOY FOODS & STOMACH CANCER RISK

There is a great deal of interest regarding the potential effects of soy-based foods (like tofu and soy beverages) on cancer risk.  As discussed in my forthcoming book (“A Cancer Prevention Guide for the Human Race”), there is a growing body of laboratory and human research data suggesting that dietary soy isoflavones might be able to reduce the risk of prostate and breast cancer.

Now, a newly published clinical research study from Korea suggests that high levels of soy isoflavones in the blood may also be linked to a reduced risk of stomach cancer, as well.  (Korea has one of the highest incidences of stomach cancer in the world.)  This study appears in the current issue of the journal Cancer Epidemiology, Biomarkers & Prevention.

As most of the published research in the area of cancer prevention is based upon the subjective recall of patient volunteers regarding their diet (and other habits), the authors of this study chose, instead, to directly measure the levels of soy isoflavones in the blood of patient volunteers.  This study included 131 patients with recently diagnosed stomach cancer, and 393 “control” patients who did not have stomach (gastric) cancer.  Blood levels of the two major dietary soy isoflavones (genistein and daidzein) were directly measured in all 524 of these research volunteers, and these results were compared between the patients with stomach cancer and the “control” patients without gastric cancer.

Study volunteers with the highest levels of genistein in their blood, when compared with those with the lowest levels, were found to be 46 percent less likely to be diagnosed with stomach cancer.  Even more impressive was the finding that study volunteers with the highest daidzein blood levels were 79 percent less likely to be diagnosed with stomach cancer when compared to the volunteers with the lowest levels of daidzen in their blood

While there may be other health-related factors at work among the study volunteers with high levels of soy isoflavones in their blood that could explain the much lower stomach cancer risk observed in these same patients, this study’s results are nonetheless intriguing enough to justify a large scale, prospective, randomized, placebo-controlled soy isoflavone clinical research study to confirm the findings of this relatively small Korean public health study.

 

To learn more about the role of soy isoflavones as potential cancer prevention nutrients, look for the publication of my new landmark evidence-based book, “A Cancer Prevention Guide for the Human Race,” in the summer of this year.





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


Dr. Wascher is an oncologic surgeon, a professor of surgery, a cancer researcher, an oncology consultant, and a widely published author



For a different perspective on Dr. Wascher, please click on the following YouTube link: 

http://www.youtube.com/watch?v=7-Tdv7XW0qg



I and the staff of Weekly Health Update would like to take this opportunity to thank the nearly 120,000 new and returning readers who visited our premier global health information website last month.  As always, we enjoy receiving your stimulating feedback and questions, and I will continue to try and personally answer as many of your inquiries as I possibly can. 


 

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Soy Isoflavones & Recurrent Prostate Cancer

February 28, 2010 by Robert Wascher  
Filed under prostate cancer

 

Welcome to Weekly Health Update



“A critical weekly review of important new research findings for health-conscious readers” 


SOY ISOFLAVONES & RECURRENT PROSTATE CANCER

 

The interest level in natural and complementary treatments for cancer has never been higher in the medical and scientific communities than it is now.  For decades, now, this area of research was often relegated to the fringes of the clinical research community, while most mainstream academic research centers and Big Pharma companies focused on the design and testing of new biochemical therapies with improved therapeutic and safety profiles.  With the 5-year overall survival rate among all patients with cancer approaching a record 65 percent, we have, unquestionably, made enormous improvement in our ability to cure many of the cancers that, not too long ago, were associated with a very high risk of death.  Cancer physicians also have far more effective medications available now to control the noxious side effects of many of our “front-line” cancer therapies, which have had the beneficial effect of further reducing suffering and morbidity among thousands of cancer patients as they undergo their daily treatments. 

Despite the  admirable (and ongoing) progress that has been achieved over the past four decades in cancer care, however, nearly 600,000 cancer patients will still succumb to their disease this year in the United States, alone.  Thus, more effective cancer prevention strategies are necessary to reduce the number of new cases of cancer, and more effective (and less toxic) cancer therapies must be identified.  Moreover, with the annual cost of many new cancer therapies now running into the hundreds-of-thousands of dollars per patient, per year, our already unsustainable (and still rising) health care costs demand that the cancer care community rigorously evaluate less costly approaches to cancer prevention and treatment.

Because so-called “natural products” are relatively inexpensive, widely available, and generally non-toxic, there is a growing interest in studying these agents using the same high-level prospective, randomized clinical trials that are routinely used by pharmaceutical companies and academic medical centers to evaluate promising new drug therapies.  Because of their great complexity and high cost, however, randomized clinical trials are best reserved for studying novel therapies for which there is at least some laboratory (“preclinical”) or early-phase clinical data available that suggests some potential benefit to humans.  Until recently, however, and most likely due to inherent biases against natural products by the mainstream clinical research community in the past, very little high-level clinical research has been performed to definitively evaluate natural products as disease prevention and treatment agents.  Fortunately, and despite shrinking research funding over the past decade, there has been a recent surge in the number of large randomized, prospective, controlled clinical research trials reporting their findings of the effects of natural products on disease prevention and treatment.

As the vast majority of natural products and lifestyle-related research in the past has been based upon low-powered research methods, it should come as no surprise that recent high-level prospective clinical research studies have, more often than not, found little or no benefit associated with the use of many of these supplements and products.  (Moreover, in some cases, several very popular and highly recommended vitamins and dietary supplements have actually been found to be potentially harmful.)   However, a great deal of promising high-level clinical research has yet to be done in order to fully and accurately assess the, literally, hundreds of natural products for which there is at least some preclinical data supporting potentially beneficial health effects.  (In my forthcoming book, “A Cancer Prevention Guide for the Human Race,” I will be comprehensively reviewing and analyzing the available laboratory and clinical research data on natural products and lifestyle strategies as an integral approach to a cancer prevention lifestyle.  The publication of this groundbreaking and authoritative evidence-based cancer prevention guide is tentatively scheduled for May of this year.)

 

In many respects, prostate cancer is the male counterpart of breast cancer in women.  Analogous to breast cancer in women, prostate cancer is the most common cancer that occurs in men (excluding minor skin cancers), and the second most common cause of cancer death.  In 2009, an estimated 192,000 new cases of prostate cancer were diagnosed in the United States alone, and approximately 27,000 American men died of this disease in the same year.  In most industrialized nations, prostate cancer accounts for approximately 25 percent of all cancer diagnoses in men (similar to the percentage of breast cancer cases among all cancer cases diagnosed in women).

A newly published prospective, early-phase, clinical pilot study from Canada evaluated the effects of a soy beverage (“soy milk”) on the progression of recurrent prostate cancer in 29 men following radiation therapy for their cancers.  This study, which has just been published in the journal Nutrition and Cancer, was not a placebo-controlled randomized study, however, this small phase II clinical study prospectively followed these patient volunteers for 6 months, during which time serial measurements of the level of prostate-specific antigen (PSA) in their blood was performed (PSA is the primary prostate tumor marker that is measured both to detect early prostate cancer and to identify recurrences of this type of cancer.)

The time interval during which the level of PSA in the blood doubles is an important indicator of the rate of progression of recurrent prostate cancer.  In this small prospective clinical pilot study, the consumption of approximately 500 ml of soy beverage per day, for 6 months, was associated with an actual decline in PSA levels in 4 (14 percent) of these patient volunteers, while another 8 (28 percent) of these recurrent prostate cancer patients experienced a greater than 100 percent increase in their PSA doubling times.  However, another 5 patients (17 percent) experienced a 50 percent or greater decrease in their PSA doubling times during the 6 month duration of this study, which was an unfavorable development.  Thus, during the brief duration of this intriguing small pilot study, 42 percent of men with early recurrence of their prostate cancer experienced either a decrease in the biochemical extent of their recurrent cancers or a significant biochemical slowing of the progression of their recurrent disease.

Whether or not longer durations of soy intake will be able to sustain the impressive results of this study is not clear at this time.  More importantly, whether or not these observed favorable effects of daily soy intake on PSA levels and PSA doubling times will actually translate into prolonged survival (or not) is also unknown at this time.  It will require several larger and longer-term randomized, placebo-controlled, blinded, prospective clinical trials of soy foods and soy isoflavone supplements to answer these critical questions (several of which are already underway).  Meanwhile, the overall safety profile for moderate amounts of soy intake in men appears to be quite favorable, and so many prostate cancer experts are cautiously recommending soy-derived foods for men with prostate cancer, and for men who are at an increased risk of developing prostate cancer, pending the completion of these larger prostate cancer research studies.

For a much more detailed and comprehensive evaluation of the role of soy foods, and other dietary supplements and lifestyle modifications, in the prevention of prostate cancer (and other cancers), look for the publication of “A Cancer Prevention Guide for the Human Race” in the spring of this year.


I and the staff of Weekly Health Update would like to take this opportunity to thank the more than 100,000 new and returning readers who have visited our premier global health information website this month, alone.  As always, we enjoy receiving your feedback and questions, and I continue to try to personally answer as many of your inquiries as I possibly can.


In view of the extreme devastation and human misery brought about in Haiti and Chile by the recent earthquakes, Weekly Health Update asks our tens of thousands of caring readers to give generously to established charities that are currently working in that country to assist the injured, the ill, and the homeless there.  There are many such legitimate charities, including the following two:

http://www.redcross.org/

http://www.imcworldwide.org/haiti


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

Dr. Wascher is an oncologic surgeon, a professor of surgery, a cancer researcher, an oncology consultant, and a widely published author

For a somewhat lighter perspective on Dr. Wascher, please click on the following YouTube link: 

http://www.youtube.com/watch?v=7-Tdv7XW0qg




 

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Soy Isoflavones Reduce Breast Cancer Recurrence Risk

Welcome to Weekly Health Update



 

“A critical weekly review of important new research findings for health-conscious readers”


SOY ISOFLAVONES REDUCE BREAST CANCER

RECURRENCE RISK

 

 

Regular readers of this column are already aware of the controversy surrounding soy isoflavone intake and breast cancer risk.  As happens frequently in clinical research (unfortunately), contradictory research findings have made it difficult to understand the true relationship between dietary soy intake and breast cancer risk (if one exists).  There is, for example, both laboratory and clinical data suggesting that a diet rich in soybean-derived products may be associated with a lower risk of developing breast cancer.  At the same time, because genistein and other dietary isoflavones are known to weakly mimic the effects of estrogen, there has been some concern that a diet rich in isoflavone “phytoestrogens” may increase both the risk of developing a new breast cancer and the risk of developing a recurrence of a previous breast cancer.  (In fact, there is data from laboratory research studies showing that genistein can indeed fuel the growth of human breast cancer cells growing in culture dishes, when exposed to high concentrations of this soy-derived isoflavone.)

 

A growing body of public health research, primarily from Asian countries where tofu and other soy-based foods are frequently consumed, appears to link increased soy consumption with a decreased lifetime breast cancer risk, particularly when soy-based foods are consumed during adolescence, during the time when development of the female breast is most active (Soy & Breast Cancer Risk).  (Interestingly, there is also recent research suggesting that soy products might also reduce the risk of prostate cancer, which is another hormonally driven cancer:   Genistein & Prostate Cancer Cells, Dietary Soy & Prostate Cancer Risk.)

 

Although epidemiological research is, increasingly, suggesting that a diet rich in soybean-derived foods might lower a woman’s lifetime risk of developing breast cancer, many breast cancer experts have remained apprehensive regarding dietary isoflavone intake in women with a prior history of breast cancer, in view of the estrogen-like effects of these “phytoestrogens.”  As I have already noted, there is considerable research data available to suggest that soy-derived isoflavones can, at least under certain laboratory conditions, stimulate estrogen-sensitive breast cancer cells to grow and divide.  These research findings have left many oncologists feeling uncomfortable in recommending soy-based foods to their breast cancer patients.  Now, a newly publish public health study in the Journal of the American Medical Association suggests that soy-based foods may actually reduce the risk of breast cancer recurrence, and death due to any cause, in women who have previously been diagnosed with this very common form of cancer.

 

In this study, which was performed in Shanghai, China, 5,042 female breast cancer survivors (ages 20 to 75 years) were followed for an average of almost 4 years.  All of these patient volunteers underwent detailed surveys regarding their lifestyle habits, including their diets.  These patients, who were originally diagnosed with breast cancer between 2002 and 2006, were surveyed at 6, 18, 36 and 60 months following their original diagnosis with breast cancer.  

 

The results of this study indicate that the breast cancer survivors who consumed the greatest amount of soy-based foods in their daily diets were 32 percent less likely to experience a recurrence of their breast cancer when compared to the women who consumed the least amount of soy-based isoflavones.  Moreover, the women who consumed the greatest amount of soy were also 29 percent less likely to die, from any cause, when compared to the women who consumed the least amount of soy-derived foods.

 

A particularly interesting and unexpected finding of this study was that both women with estrogen sensitive breast cancers and women with tumors that were not sensitive to estrogen appeared to experience a significantly decreased risk of breast cancer recurrence if they frequently consumed soy products.  Another important finding of this study was that women who were taking the estrogen-blocking cancer treatment drug tamoxifen also appeared to enjoy a reduced risk of breast cancer recurrence with higher levels of dietary soy intake.  Additionally, the researchers noted that high levels of soy intake appeared to be about as effective in reducing the risk of breast cancer recurrence as the breast cancer prevention drug tamoxifen, alone.

 

The results of this very important study mirror the findings of the only other prospective clinical study that has looked at the impact of soy-based foods on breast cancer recurrence (the “Life After Cancer Epidemiology,” or “LACE,” study).  The LACE study, which was performed in the United States, followed nearly 2,000 breast cancer survivors for, on average, more than 6 years.  In the LACE study, women who were taking tamoxifen, and who also consumed the highest amount of soy-based dietary isoflavones, were 50 percent less likely to develop a recurrence of their breast cancer when compared to women who reported the lowest consumption of soy-derived foods.

 

As I have pointed out previously, epidemiological research studies based upon dietary surveys are susceptible to several types of bias which, in turn, can cause researchers to draw the wrong conclusions.  In this case, however, there are now two large prospective cohort studies that have reached essentially the same conclusions (albeit with a rather limited duration of patient follow-up).  Both studies strongly suggest that high levels of soy-based isoflavones in the diet may be able to significantly reduce the risk of breast cancer recurrence.  Based upon the findings of this large Chinese study, the apparent cancer risk reduction effect associated with high levels of soy intake also appears to benefit premenopausal and postmenopausal women, as well as women who are taking the estrogen-blocking drug tamoxifen, women with estrogen-sensitive tumors, and women with (counter-intuitively) estrogen-resistant tumors.

 

In view of the limited duration of patient follow-up in both of these clinical breast cancer studies, as well as the limitations of survey-based epidemiological research in general, I would like to see updated data from both of these studies after at least 10 years of patient observation before I would be willing to tell my breast cancer patients that they should significantly increase their dietary soy intake.  On the other hand, the rather compelling data presented by both of these clinical research studies will also make me less anxious when any of my breast cancer patients decide, of their own accord, to increase their intake of soy-derived isoflavones.

 

 

Note:  Weekly Health Update is currently undergoing an extensive upgrade to better serve its tens of thousands of health-conscious readers around the world.  Beginning in January 2010, newly archived columns will be available by selecting the “Archives” tab on the right side of your screen (all archived columns prior to January 2010 will continue to be available by selecting the “Archives 2007-2009” tab at the top of the screen.)


 


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


Dr. Wascher is an oncologic surgeon, a professor of surgery, a cancer researcher, an oncology consultant, and a widely published author

 

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