Soy And Breast Cancer Survivors

Written by Dr. Steve Chaney on . Posted in Soy and Breast Cancer, Soy and Cancer

Do Soy & Cruciferous Vegetables Reduce Breast Cancer Treatment-Related Symptoms?

Author: Dr. Stephen Chaney

 

soy and breast cancer survivorsThe topic of soy and breast cancer has been a controversial subject for years. If you read Dr. Strangelove’s nutrition blogs, you would be led to believe that soy causes breast cancer and shortens the lifespan of breast cancer survivors.

This is one of the many myths I have debunked in my book “Slaying The Supplement Myths.” Multiple clinical studies have proven that soy reduces the likelihood of developing breast cancer. Several clinical studies have shown it also decreases recurrence of breast cancer and enhances survival following breast cancer treatment. Other clinical studies have found no effect of soy on recurrence or longevity in breast cancer survivors. Zero studies have found any detrimental effects of soy in breast cancer survivors.

So, is there a true relationship between soy and breast cancer survivors?  These studies have all shown that soy is part of a healthy diet and should not be feared by women who have survived breast cancer.

Breast cancer survivors suffer from several treatment-related side effects. These include menopausal symptoms, fatigue, joint problems, hair thinning, and memory loss.

The most recent headlines claim that soy and cruciferous vegetables (broccoli, cauliflower, cabbage, Brussels sprouts, kale and related vegetables) decrease menopause and other treatment-related symptoms in breast cancer survivors. If you have seen those headlines, you are probably wondering:

  • Are they true?
  • Should I increase soy consumption following breast cancer treatment?

How Was The Study Designed?

soy and breast cancer survivors studyThis study (SJO Nomura et al, Breast Cancer Research and Treatment, 168: 467-479) enrolled 192 Chinese-American and 173 non-Hispanic White women in the San Francisco Bay area between 2006 and 2012. The average age of the women was 57. They were all breast cancer survivors who had been treated 1-5 years previously. Most had been treated at least 2 years previously.

The participants were recruited by mail and filled out questionnaires which provided demographic data, health information, and information on treatment-related symptoms. They also filled out a food frequency questionnaire designed to estimate intake of soy foods and cruciferous vegetables.

In terms of food consumption, the range was:

  • 0 to 24 gram/day for soy.
  • <33 grams/day to >71 grams/day for cruciferous vegetables. For reference, one serving (1/2 cup) of cooked broccoli weighs 78 grams.

 

Soy And Breast Cancer Survivors?

 

soy and breast cancer survivors dietIn looking at the effect of soy and cruciferous vegetables on treatment-related symptoms, it is important to understand that the two groups of women had different baseline characteristics.

  • The Chinese-American women had a higher average intake of both soy and cruciferous vegetables.
  • The Non-Hispanic White women were more likely to experience treatment-related worsening of menopausal symptoms.
  • The Chinese-American women were more likely to experience fatigue, joint problems, hair thinning, and memory loss.

With that in mind, here are the results of the study:

Soy intake:

  • soy and breast cancer survivors cruciferous vegetablesWhen all women in the study were grouped together, high (>24 grams/day) versus low (0 grams/day) soy intake was associated with a 57% reduction in fatigue.
  • For Non-Hispanic White women high versus low soy intake was associated with a 71% reduction in menopause symptoms and a 75% reduction in fatigue.
  • The effect of soy on treatment-related symptoms was non-significant for Chinese-American women, perhaps because the baseline intake of soy was greater for this group.

Cruciferous vegetable intake:

  • When all women in the study were grouped together, high (>71 grams/day) versus low (<33 grams/day) cruciferous vegetable intake was associated with a 50% reduction in menopause symptoms.
  • For Chinese-American women, high versus low intake of cruciferous vegetables was associated with a 39% reduction in memory loss.
  • The effect of cruciferous vegetables on treatment-related symptoms was non-significant for Non-Hispanic White women.

The authors concluded: “In this population of breast cancer survivors, higher soy and cruciferous vegetable intake was associated with less treatment-related menopausal symptoms and fatigue. To confirm study findings, additional research is needed that explores the relationship between diet and breast cancer treatment-related symptoms…in a larger, diverse study population.”

What Does This Study Mean For You?

soy and breast cancer survivors meaning for youThis is a small, preliminary study that needs to be repeated before any definitive recommendations can be made. Here are my take-home points from this study.

  • Soy is an excellent source of high-quality plant protein. We already know there is no reason to avoid soy following breast cancer treatment. This study provides another reason to include soy as part of a healthy, plant-based diet following treatment. This study also provides a rationale for including cruciferous vegetables as part of a healthy, plant-based diet following treatment.
  • However, 24 grams of soy represents a single serving of many soy foods. This study does not provide a rationale to increase soy consumption beyond a single serving.
  • The danger after studies like this are publicized is that breast cancer survivors will just focus on soy and cruciferous vegetables in their diet. This study looked at the effects of soy and cruciferous vegetables based on their potential effects on menopausal symptoms. However, they are just two components of a healthy, plant-based diet, and we know that primarily plant-based diets are associated with a decreased risk of breast cancer.

In my opinion, we need to focus less on “magic bullet” approaches (single nutrients and single foods) and focus more on holistic approaches. We should be asking how holistic, healthy diets influence recovery from breast cancer and reduction of treatment-related symptoms. We should be encouraging breast cancer survivors to focus on all aspects of a healthy diet, not just soy and cruciferous vegetables.

 

The Bottom Line

 

The topic of soy and breast cancer has been a controversial subject for years. If you read Dr. Strangelove’s nutrition blogs, you would be led to believe that soy causes breast cancer and shortens the lifespan of breast cancer survivors.

This is one of the many myths I have debunked in my book “Slaying The Supplement Myths.” Multiple clinical studies have shown that soy is part of a healthy diet and should not be feared by women who have survived breast cancer.

The most recent headlines claim that soy and cruciferous vegetables (broccoli, cauliflower, cabbage, Brussels sprouts, kale and related vegetables) decrease menopause symptoms and fatigue in breast cancer survivors.

These headlines are based on a small, preliminary study that needs to be repeated before any definitive recommendations can be made. Here are my take-home points from this study.

  • Soy is an excellent source of high-quality plant protein. We already know there is no reason to avoid soy following breast cancer treatment. This study provides another reason to include soy as part of a healthy, plant-based diet following treatment. This study also provides a rationale for including cruciferous vegetables as part of a healthy, plant-based diet following treatment.
  • However, 24 grams of soy represents a single serving of many soy foods. This study does not provide a rationale for increasing soy consumption beyond a single serving.
  • This study focused on soy and cruciferous vegetables based on their potential effects on menopausal symptoms. However, they are just two components of a healthy, plant-based diet, and we know that primarily plant-based diets are associated with a decreased risk of breast cancer. In my opinion, we need to focus less on “magic bullet” approaches (single nutrients and single foods) and focus more on holistic approaches. We should be asking how healthy diets influence recovery from breast cancer and reduction of treatment-related symptoms.

For more details read the article above.

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

Does Soy Increase Breast Cancer Risk?

Written by Dr. Steve Chaney on . Posted in Soy and Breast Cancer

What Does the Latest Study Say?

Author: Dr. Stephen Chaney

does soy increase breast cancer riskDoes soy increase breast cancer risk?

“To soy or not to soy. That is the question.” If you are a woman, particularly a woman with breast cancer, it is an important question. Some experts say soy should be avoided at all costs. They say that soy will increase your risk of breast cancer. Other experts say soy is perfectly safe and may even reduce your risk of breast cancer.

If you are a breast cancer survivor, the question of whether soy increases or decreases your risk of disease recurrence is even more crucial. You have already endured surgery, chemotherapy, and/or radiation. You never want to go through that again.

 

Why Is There So Much Confusion About Soy?

soy confusionSoy isoflavones decrease estrogen production, strengthen the immune system, inhibit cell proliferation, and reduce the production of reactive oxygen species. These are all effects that might reduce breast cancer risk.

On the other hand, soy isoflavones also bind to estrogen receptors and exhibit weak estrogenic activity. This effect has the potential to increase breast cancer risk.

Cell culture and animal studies have only confused the issue. Soy isoflavones stimulate the growth of breast cancer cells in a petri dish. Soy isoflavones also stimulate breast cancer growth in a special strain of mice lacking an immune system. However, in studies in both mice and rats with a functioning immune system, soy isoflavones decreased breast cancer risk.

The confusion has been amplified by claims and counter-claims on the internet. There are bloggers who are more interested in the spectacular than they are in accuracy (Today we call this fake news). They have taken the very weak evidence that soy isoflavones could possibly increase breast cancer risk and have blown it all out of proportion.

Their blogs claimed that soy definitely increased breast cancer risk and should be avoided at all cost. Their claims were picked up by other web sites. Eventually, the claims were repeated so many times that people started to believe them. A “myth”was created.  I call it a myth, because it was never based on convincing scientific evidence.

In the meantime, scientists looked at the cell culture and animal studies and took a more responsible approach. They said “If this is true, it is an important public health issue. We need to do clinical trials in humans to test this hypothesis.”

It is easy to see why the general public still asks “Does soy increase breast cancer risk?”

 

breast cancer soyWhat Have Previous Clinical Studies Shown?

The question “Does soy increased breast cancer risk” was settled a long time ago. Some studies have shown no effect of soy consumption on breast cancer risk. Others have reported that soy consumption decreased breast cancer risk. A meta-analysis of 18 previous clinical studies found that soy slightly decreased the risk of developing breast cancer (J Natl Cancer Inst, 98: 459-471, 2006 Meta-Analysis-of-Soy-Intake-and-Breast-Cancer-Risk). None of those studies found any evidence that soy increased the risk of breast cancer.

What about recurrence of breast cancer in women who are breast cancer survivors? Between 2006 and 2013 there have been five major clinical studies (soy-and-breast-cancer-recurrence) looking at the effects of soy consumption on breast cancer recurrence in both Chinese and American populations. Once again, the studies have shown either no effect of soy on breast cancer recurrence or a protective effect. None of them have shown any detrimental effects of soy consumption for breast cancer survivors.

A meta-analysis of all 5 studies was published in 2013 (Chi et al, Asian Pac J Cancer Prev., 14: 2407-2412, 2013). This study combined the data from 11,206 breast cancer survivors in the US and China. Those with the highest soy consumption had a 23% decrease in recurrence and a 15% decrease in mortality from breast cancer.

 

breast cancer soy studyWhat Did The Latest Study Show?

In previous clinical studies the protective effect of soy has been greater in Asian populations than in North American populations. This could have been because Asians consume more soy. However, it could be due to other population differences as well. To better evaluate the effect of soy consumption on breast cancer survivors in the North America, this group of investigators correlated soy consumption with all-cause mortality in breast cancer survivors in the US and Canada (Zhang et al, Cancer, DOI: 10.1002/cncr.30615, March 2017).

The data was collected from The Breast Cancer Family Registry, an international research infrastructure established in 1995. The women enrolled in this registry either had been recently diagnosed with breast cancer or had a family history of breast cancer.

This study included 6235 breast cancer survivors from the registry who lived in the San Francisco Bay area and the province of Ontario in Canada. The women represented an ethnically diverse population and had a median age of 51.8 at enrollment.  Soy consumption was assessed either at the time of enrollment or immediately following breast cancer diagnosis. The women were followed for 9.4 years, during which time 1224 of them died.

The results were as follows:

  • There was a 21% decrease in all-cause mortality for women who had the highest soy consumption compared to those with the lowest soy consumption.
  • The protective effect of soy was strongest for those women who had receptor negative breast cancer. This is significant because receptor-negative breast cancer is associated with poorer survival rates than hormone receptor-positive cases.
  • The protective effect was also greatest (35% reduction in all-cause mortality) for women with the highest soy consumption following breast cancer diagnosis. This suggests that soy may play an important role in breast cancer survival.
  • The authors concluded “In this large, ethnically diverse cohort of women with breast cancer, higher dietary intake of [soy] was associated with reduced total mortality.”

In an accompanying editorial, Omer Kucuk, MD, of the Winship Cancer Institute of Emory University, noted that the United States is the number 1 soy producer in the world and is in a great position to initiate changes in health policy by encouraging soy intake.  He said “We now have evidence that soy foods not only prevent breast cancer but also benefit women who have breast cancer. Therefore, we can recommend women to consume soy foods because of soy’s many health benefits.”  In light of this study, has the question “Does soy increase breast cancer risk” been answered?

 

Does Soy Increase Breast Cancer Risk?

soy breast cancer mythEvery clinical study has its limitations. If there were only one or two studies, the question of whether soy increases breast cancer risk might still be in doubt. However, multiple clinical studies have come to the same conclusion. Either soy has no effect on breast cancer risk and breast cancer recurrence, or it has a protective effect.

Not a single clinical study has found any evidence that soy increases breast cancer risk. It is clear that consumption of soy foods is safe, and may be beneficial for women with breast cancer. The myth that soy increases breast cancer risk needs to be put to rest.

On the other hand, we should not think of soy as a miracle food. Breast cancer risk is also decreased by a diet that:

  • Contains lots of fruits and vegetables.
  • Is low in processed grains & sweets and high in whole grains.
  • Is low in saturated & trans fats and high in omega-3 and monounsaturated fats.
  • Is low in red & processed meats and high in beans, fish & chicken.

Furthermore, diet is just one component of a holistic approach for reducing the risk of breast cancer. In addition to a healthy diet, the American Cancer Society recommends that you:

  • Control your weight
  • Be physically active
  • Limit alcohol
  • Don’t smoke
  • Limit hormone replacement therapy unless absolutely necessary.
  • Reduce stress

Does soy increase breast cancer risk?  No.

The Bottom Line

 

  • It is time to put the myth that soy increases breast cancer risk to rest. This myth is based on cell culture and animal studies, and those studies were inconclusive.
  • Multiple clinical studies have shown that soy either has no effect on breast cancer risk, or that it reduces the risk.
  • Multiple clinical studies have also shown that soy either has no effect on breast cancer recurrence in women who are breast cancer survivors, or that it reduces recurrence.
  • The latest clinical study is fully consistent with previous studies. It reports:
    • There was a 21% decrease in all-cause mortality for women who had the highest soy consumption compared to those with the lowest soy consumption.
    • The protective effect of soy was strongest for those women who had receptor negative breast cancer. This is significant because receptor-negative breast cancer is associated with poorer survival rates than hormone receptor-positive cases.
    • The protective effect was also greatest (35% reduction in all-cause mortality) for women with the highest soy consumption following breast cancer diagnosis. This suggests that soy may play an important role in breast cancer survival.
  • No clinical studies have provided any evidence to support the claim that soy increases either breast cancer risk or breast cancer recurrence.
  • On the other hand, we should not think of soy as a miracle food. Breast cancer risk is also decreased by a diet that:
    • Contains lots of fruits and vegetables.
    • Is low in processed grains & sweets and high in whole grains.
    • Is low in saturated & trans fats and high in omega-3 and monounsaturated fats.
    • Is low in red & processed meats and high in beans, fish & chicken
  • Furthermore, diet is just one component of a holistic approach for reducing the risk of breast cancer. In addition to a healthy diet, the American Cancer Society recommends that you:
    • Control your weight
    • Be physically active
    • Limit alcohol
    • Don’t smoke
    • Limit hormone replacement therapy unless absolutely necessary.
    • Reduce stress

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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Latest Article

Can Plant-based Diets Be Unhealthy?

Posted September 10, 2019 by Dr. Steve Chaney

Do Plant-Based Diets Reduce Heart Disease Deaths?

Author: Dr. Stephen Chaney

 

plant-based diets vegetablesPlant-based diets have become the “Golden Boys” of the diet world. They are the diets most often recommended by knowledgeable health and nutrition professionals. I’m not talking about all the “Dr. Strangeloves” who pitch weird diets in books and the internet. I am talking legitimate experts who have spent their life studying the impact of nutrition on our health.

Certainly, there is an overwhelming body of evidence supporting the claim that plant-based diets are healthy. Going on a plant-based diet can help you lower blood pressure, inflammation, cholesterol and triglycerides. People who consume a plant-based diet for a lifetime weigh less and have decreased risk of heart disease, diabetes, and cancer.

But, can a plant-based diet be unhealthy? Some people consider a plant-based diet to simply be the absence of meat and other animal foods. Is just replacing animal foods with plant-based foods enough to make a diet healthy?

Maybe not. After all, sugar and white flour are plant-based food ingredients. Fake meats of all kinds abound in our grocery stores. Some are very wholesome, but others are little more than vegetarian junk food. If you replace animal foods with plant-based sweets, desserts, and junk food, is your diet really healthier?

While the answer to that question seems obvious, very few studies have asked that question. Most studies on the benefits of plant-based diets have compared population groups that eat a strictly plant-based diet (Seventh-Day Adventists, vegans, or vegetarians) with the general public. They have not looked at variations in plant food consumption within the general public. Nor have they compared people who consume healthy and unhealthy plant foods.

This study (H Kim et al, Journal of the American Heart Association, 8:e012865, 2019) was designed to fill that void.

 

How Was The Study Done?

plant-based diets studyThis study used data collected from 12,168 middle aged adults in the ARIC (Atherosclerosis Risk in Communities) study between 1987 and 2016.

The participant’s usual intake of foods and beverages was assessed by trained interviewers using a food frequency questionnaire at the time of entry into the study and again 6 years later.

Participants were asked to indicate the frequency with which they consumed 66 foods and beverages of a defined serving size in the previous year. Visual guides were provided to help participants estimate portion sizes.

The participant’s adherence to a plant-based diet was assessed using four different well-established plant-based diet scores. For the sake of simplicity, I will include 3 of them in this review.

  • The PDI (Plant-Based Diet Index) categorizes foods as either plant foods or animal foods. A high PDI score means that the participant’s diet contains more plant foods than animal foods. A low PDI score means the participant’s diet contains more animal foods than plant foods.
  • The hPDI (healthy plant-based diet index) is based on the PDI but emphasizes “healthy” plant foods. A high hPDI score means that the participant’s diet is high in healthy plant foods (whole grains, fruits, vegetables, nuts, legumes, coffee and tea) and low in animal foods.
  • The uPDI (unhealthy plant-based diet index) is based on the PDI but emphasizes “unhealthy” plant foods. A high uPDI score means that the participant’s diet is high in unhealthy plant foods (refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts) and low in animal foods.

For statistical analysis the scores from the various plant-based diet indices were divided into 5 equal groups. In each case, the group with the highest score consumed the most plant foods and least animal foods. The group with the lowest score consumed the least plant foods and the most animal foods.

The health outcomes measured in this study were heart disease events, heart disease deaths, and all-cause deaths. Again, for the sake of simplicity, I will only include 2 of these outcomes (heart disease deaths and all-cause deaths) in this review. The data on deaths were obtained from state death records and the National Death Index. (Yes, your personal information is available on the web even after you die.)

 

Do Plant-Based Diets Reduce Heart Disease Deaths?

plant-based diets reduce heart deathsThe participants in this study were followed for an average of 25 years.

The investigators looked at heart disease deaths over the 25 years and compared people with the highest intake of plant foods to people with the highest intake of red meat and other animal foods. The results were:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods (whole grains, fruits, vegetables, nuts, legumes, coffee and tea) had a 19-32% lower risk of dying from heart disease than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods (refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts) had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

When the investigators looked at all-cause deaths over the 25 years:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods had an 11-25% lower risk of dying from any cause than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

What Else Did The Study Show?

The investigators made a couple of other interesting observations:

  • The association of the overall diet with heart disease and all-cause deaths was stronger than the association of individual food components. This underscores the importance of looking at the effect of the whole diet on health outcomes rather than the “magic” foods you hear about on Dr. Strangelove’s Health Blog.
  • Diets with the highest amount of healthy plant foods were associated with higher intake of carbohydrates, plant protein, fiber, and micronutrients, including potassium, magnesium, iron, vitamin A, vitamin C, folate, and lower intake of saturated fat and cholesterol.
  • Diets with the highest amount of unhealthy plant foods were associated with higher intake of calories and carbohydrates and lower intake of fiber and micronutrients.

The last two observations may help explain some of the health benefits of plant-based diets.

 

Can Plant-Based Diets Be Unhealthy?

plant-based diets unhealthy cookiesNow, let’s return to the question I asked at the beginning of this article: “Can plant-based diets be unhealthy?” Although some previous studies have suggested that unhealthy plant-based diets might increase the risk of heart disease, this study did not show that.

What this study did show was that an unhealthy plant-based diet was no better for you than a diet containing lots of red meat and other animal foods.

If this were the only conclusion from this study, it might be considered a neutral result. However, this result clearly contrasts with the data from this study and many others showing that both plant-based diets in general and healthy plant-based diets reduce the risk of heart disease deaths and all-cause deaths compared to animal-based diets.

The main message from this study is clear.

  • Replacing red meat and other animal foods with plant foods can be a healthier choice, but only if they are whole, minimally processed plant foods like whole grains, fruits, vegetables, nuts, legumes, coffee and tea.
  • If the plant foods are refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts, all bets are off. You may be just as unhealthy as if you kept eating a diet high in red meat and other animal foods.

There is one other subtle message from this study. This study did not compare vegans with the general public. Everyone in the study was the general public. Nobody in the study was consuming a 100% plant-based diet.

For example:

  • The group with the highest intake of plant foods consumed 9 servings per day of plant foods and 3.6 servings per day of animal foods.
  • The group with the lowest intake of plant foods consumed 5.4 servings per day of plant foods and 5.6 servings per day of animal foods.

In other words, you don’t need to be a vegan purist to experience health benefits from adding more whole, minimally processed plant foods to your diet.

 

The Bottom Line

A recent study analyzed the effect of consuming plant foods on heart disease deaths and all-cause deaths over a 25-year period.

When the investigators looked at heart disease deaths over the 25 years:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods had a 19-32% lower risk of dying from heart disease than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

When the investigators looked at all-cause deaths over the 25 years:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods had an 11-25% lower risk of dying from any cause than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

The main message from this study is clear.

  • Replacing red meat and other animal foods with plant foods can be a healthier choice, but only if they are whole, minimally processed plant foods like whole grains, fruits, vegetables, nuts, legumes, coffee and tea.
  • If the plant foods are refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts, all bets are off. You may be just as unhealthy as if you kept eating a diet high in red meat and other animal foods.

A more subtle message from the study is that you don’t need to be a vegan purist to experience health benefits from adding more whole, minimally processed plant foods to your diet. The people in this study were not following some special diet. The only difference was that some of the people in this study ate more plant foods and others more animal foods.

For more details on the study, read the article above.

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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