Patterns Of Soy Consumption
Of the 300,852 female participants, 44.5% resided in urban areas, and the mean age at baseline was 50.9 years . At baseline, 12.0% reported never/rarely consuming soy foods and 9.3% reported a regular consumption . The estimated mean value of usual soy isoflavone intake was 9.4 mg/day, corresponding to 7.5 g/day of soybean equivalents. The spearman coefficient between baseline frequency group and usual amount quartile of soy intake was 0.76. Women consuming soy more frequently were more likely to live in urban areas, to have a higher level of education, and higher household income. They were also more likely to be taller, to have a family history of cancer, to be regular consumers of fresh fruit, red meat, fish and dairy products, and to have higher total energy intake. There were no obvious variation in age, BMI, level of physical activity and reproductive characteristics between soy consumption categories. Few of the women were ever smoker or weekly alcohol consumers.
Table 1 Baseline characteristics of participants by baseline frequency of soy consumptiona
How To Incorporate More Soy Into Your Diet
A diet rich in soy can be healthy, delicious, and fulfilling. Eating soy goes beyond enjoying a block of tofu. Here are some forms of soy you can incorporate into your diet:
- Soy milk. Try using soy milk as a replacement for animal milk in your cereal, your coffee, or even your baking.
- Extra-firm tofu. This form of tofu can be a great replacement for animal protein in your main courses. Alternatively,
- Soft-tofu. This form of tofu is a delicious add-in for soups and stews.
- Soy cheese. If you are sensitive to dairy or looking to cut back on your intake of cheese, consider eating soy cheese as a replacement.
- Miso. This is a great base for soup stocks, salmon marinades, and even desserts.
- Natto. If youre feeling extra adventurous, the fermented soybean called natto can be found at most Asian grocery stores. It is great over rice, in sushi, or with curry.
- Tempeh. Another meat substitute, tempeh, is a delicious and protein-packed addition to any meal.
- Soy sauce. This is another great base for marinades, soups, dressings, or dipping sauces.
It is worth noting that most of the studies regarding soy as a cancer-fighting food are observational, and more detailed studies need to be done. The relationship between soy consumption and breast health may additionally be related to the lifestyle and other dietary habits of people who eat soy products.
While there is no link believed to exist between soy and breast cancer, there might be other reasons for you to consider eating less soy.
Myth: All Types Of Soy Have The Same Effect On The Body
Your body may process the natural soy in tofu, miso, and soy milk differently than the kind thatâs added to processed foods.
The soy protein isolate found in supplements, protein powders, and meat substitutes is usually stripped of nutrients, such as fiber.
âItâs also a more concentrated form of soy,â Millstine says. âSo youâre much more likely to get a high dose if youâre having protein shakes and soy hot dogs than if youâre eating edamame.â
Researchers arenât certain how large amounts of soy affect breast cancer risk. In one early study, soy supplements were shown to âswitch onâ genes that encourage cancer growth in women with early-stage breast cancer.
Experts recommend sticking with a moderate amount, or about one to two servings, of whole soy a day. One serving includes:
- Half a cup of cooked edamame
- 1 cup of soy milk
- 1 ounce of soy nuts
- 3 ounces of tofu
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What Is Komen Doing
According to Komen Scholar, Carol Fabian, M.D., Professor, Department of Internal Medicine at the University of Kansas Medical Center, After more than three decades of asking questions about the role of soy in breast cancer risk and recurrence we still do not have the answers. Thus Komens role in funding research on soy and other weak estrogen-like substances in plants is very important. It is possible that the soy may help prevent breast cancer if soy ingestion is started at a young age, but the primary concern has been in postmenopausal breast cancer survivors and the potential for soy to have an estrogen like action on the cancer cells if any remain. Although research is ongoing, there is little evidence to suggest that there is danger in consuming moderate amounts of soy in food even for survivors. However, until more is known it is probably best to avoid soy supplements after a breast cancer diagnosis.
Komen has invested more than $3.3 million in research investigating the effects of soy, and its components, on various aspects of breast cancer. Studies include:
- Determining how soy affects breast cancer risk, including studies on high soy or soy-supplemented diets.
- Testing whether soy, or its active components can protect against genetic damage and prevent the development of breast cancer.
- Testing whether soy can enhance the effectiveness of breast cancer treatments or prevent drug resistance.
Intake Of Soy Soy Isoflavones And Soy Protein And Risk Of Cancer Incidence
Forty seven studies examined the association between soy, soy isoflavones and soy protein intake and cancer risk . The pooled results showed that a higher intake of soy was significantly associated with a 10% reduced risk of overall cancer incidence when comparing extreme categories of soy intake . There was significant heterogeneity across the studies . The dose-response analysis revealed that each increase of 25 g/d in soy intake significantly decreased the risk of overall cancer incidence by 4% . In the stratified analyses across study and participant characteristics, inconsistencies in these variables did not significantly alter the shape of association between soy intake and risk of overall cancer incidence . In terms of soy isoflavones and soy protein, participants in the highest category of soy isoflavones intake had 6% lower risk of overall cancer incidence, compared with those in the lowest category . Evidence of substantial heterogeneity existed among studies . No significant association between soy protein consumption and risk of overall cancer incidence was observed . Each 10 mg/d increment of soy isoflavones intake was significantly associated with a 4% lower risk of overall cancer incidence in the dose-response analysis . The association between soy isoflavones intake and risk of overall cancer incidence did not differ substantially by characteristics of study and participant examined .
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Soy And Cancer: Should We Worry Heres What The Recent Literature Says
May 20, 2022
When a client says I am concerned about including soy products in my plant-based diet because of the cancer risk, this is the information I can provide them.
In short: no, you should not avoid eating soy for fear of increasing your cancer risk. Quite the opposite!
In the past, many health professionals were concerned about the potential of the plant estrogens present in soy to increase the risk of breast cancer . Studies done on rats also mislead us into thinking that soy consumption in humans would induce tumor growth. Thankfully, we now know that isoflavones interact with human estrogen receptors in different ways than actual human estrogen, and that rodents and humans process soy isoflavones differently.
We also know that regularly consuming soy products like edamame, tofu, and soy milk is NOT associated with a greater cancer risk. In fact, soy likely contributes to the prevention of various cancers and reduces the odds of recurrence.
Which Soy Foods Are Good Sources Of Isoflavones
I tell patients to stick with whole soy foods, not soy-based products. Some examples of whole soy foods are tofu, soy milk, tempeh, and edamame. Those are good sources of isoflavones. On the other hand, soy-based condiments like soy sauce and soybean oil do not contain enough isoflavones needed to get the benefits of soy. They may even be detrimental because they are high in sodium and trans fats.
And on the other end of the spectrum are soy protein isolate supplements. Soy protein isolate is a stripped-down version of soy that only contains protein and none of the other benefits. Its commonly found in protein bars and supplemental powders. Products with soy protein isolate may have higher concentrations of isoflavones than we consider safe.
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What About Soy Allergy
You should know however that soy is considered a priority allergen . If you consume soy products and start experiencing a skin reaction, tingling , abdominal symptoms, or signs of anaphylaxis, you should get medical attention. However, an expert committee from the Food and Agriculture Organization of the United Nations is recommending that soy be moved to the B list of allergens as it impacts a very small number of people globally and generally causes mild symptoms only . Aside from being very nutritious, soy can be made into many delicious dishes and seasoned in a myriad of ways, so we would be foolish to go without.
Myth: If You Have Or Had Breast Cancer Avoid All Soy Foods
Just as eating a moderate amount of whole soy doesnât make you more likely to get breast cancer, it also doesnât seem to raise your risk for recurrence.
âStill, Iâd recommend that breast cancer patients avoid soy supplements,â Millstine says.
In one report, researchers analyzed data from diet surveys completed by more than 9,500 American and Chinese women. Those who said they ate the most soy were 25% less likely to have their cancer return compared to those who had the least.
Some experts worried that soy might interfere with breast cancer drugs that lower estrogen levels, such as tamoxifen. But the same study showed that soy also protected against recurrence in patients who took tamoxifen.
The soy foods that the study included were tofu, soy milk, and fresh soybeans. As you might expect, the Chinese women ate far more of it than those in the U.S. The results still held when the researchers considered that fact.
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What About Soy Supplements
Most studies looking at soy and breast health have focused on soy foods rather than soy supplements.10
In the lab, researchers can separate soy proteins into individual compounds, called isolates. Individual isolates do not occur in nature. This is similar to say, vitamin A. While many natural things contain vitamin A, pure vitamin A does not appear in nature. Isolates, like pure vitamin A, can only be created in a lab. Because soy supplements are created in a lab, they can contain individual soy protein isolates.
Some lab studies of cells have shown that soy protein isolates may increase cancer growth.2 So, soy supplements are not currently recommended.
Soy And Cancer: Myths And Misconceptions
Karen Collins, MS, RDN, CDN, FAND is AICRs Nutrition Advisor. Karen is a speaker, writer and consultant who specializes in helping people make sense of nutrition news. You can follow her on Twitter and Facebook
Among the food myths that I am most often asked about, soy foods rate the highest on the list. Here are some of the most common myths about soy, and an update on what current research shows.
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Intake Of Soy Soy Isoflavones And Risk Of Cancer Mortality In Cancer Patients
Eight studies were included in the analysis of soy and soy isoflavones intake with risk of cancer mortality in cancer patients . All these studies reported non-significant associations. The pooled results showed that a higher intake of soy was not significantly associated with a lower risk of cancer mortality in cancer patients when comparing extreme categories of soy intake . Little evidence of heterogeneity was found . No statistically significant association was also found between soy isoflavones intake and risk of cancer mortality among cancer patients .
What Do We Know About The Relationship Between Soy And Breast Cancer
Soy has been found to not only reduce the risk of cancer but also the risk of it coming back. One study showed a 30% reduction in breast cancer recurrence risk when people consumed a moderate amount of isoflavones. I tell patients: Not only should you not avoid soy, but it could be beneficial to incorporate into your diet.
Soy has a lot of health benefits outside of cancer prevention, too. Its been associated with lowered cholesterol and reduced risk of heart disease in healthy adults and has even been shown to help stroke patients recover.
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Can Eating Soy Increase Your Risk Of Breast Cancer
Some types of cancer, such as hormone receptor-positive breast cancer, use human estrogen to grow and spread. Because of this, some people may worry that eating the phytoestrogens found in soy could increase estrogen in their bodies and encourage breast cancer growth.
However, no studies in people have shown a link between eating soy and having breast cancer. Studies done in the laboratory have shown that isoflavone enhanced the growth of breast cancer cells and promoted breast cancer tumors in rats. However, these studies were not done in people, and laboratory studies are not used to make dietary recommendations for people. Researchers have also discovered that rats metabolize soy differently than humans do.
Scientific data suggests that consuming soy foods as part of a diet with lots of other plants is a great way for breast cancer survivors to care for their bodies. However, if you’re not comfortable including soy foods, survivors can have a perfectly healthy diet that does not include soy foods. Julie LG Lanford, MPH, RD, CSO, LDN, registered dietitian and nutritionist with 15 years of experience working in oncology nutrition
Obesity Smoking Lifestyle And Genetics Are Riskier Than Soy
Unfortunately when people worry about something like soy intake when it may not be a risk for breast cancer they may not be worrying as much as they should about true risk factors.
Removing attention from these can be the greater risk, Dr. Roesch says.
These other behavioral risk factors for breast cancer like obesity, smoking at an early age, a sedentary lifestyle or high saturated fat intake are bigger concerns than consuming plant estrogens like soy, she says.
Genetics also play a major role in a persons risk of developing certain types of breast cancer.
Does Soy Lower The Risk Of Breast Cancer
Although there are not enough data to know whether soy may help protect against breast cancer, many studies suggest that it does.3-4 However, it seems the benefit only comes with a pattern of intake that is seen in most Asian countries, where women begin eating soy early life and eat it in amounts many times greater than typically seen in the U.S.4 In Japan, for example, soy intake ranges from 25 mg to around 50 mg per day. In the U.S., intake ranges from less than 1 mg to 3 mg per day.5
Results from an analysis that combined findings from multiple studies in Asian populations found that women who ate high amounts of soy had a 25 percent lower risk of breast cancer compared to those who ate lower amounts.6 When the same analyses were done in studies of U.S. and other Western populations, there was no link between soy and breast cancer risk.6
Is It Safe For Survivors
Studies of pre- and post-menopausal women suggest soy isoflavones may have a protective effect against breast cancer. Population studies indicate that soy consumption in survivors of breast cancer may be linked to decreased recurrence and greater overall survival. A 2017 study looked at more than 6,200 American and Canadian women with breast cancer. These women filled out surveys about what they ate and other lifestyle habits. Those women who ate the highest amounts of isoflavones had a 21% lower risk of having died from any cause, compared to the women who ate the lowest amount of isoflavones.
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Myth: Soy Only Affects Breast Cancers That Are Sensitive To Estrogen
While itâs true that soy isoflavones play a bigger role in estrogen-receptor positive breast cancers, early research links it to a lower risk of other types of breast cancer.
That finding comes from a study of 756 Chinese women who had breast cancer and about 1,000 others who didnât have the disease. All of the women answered questions about their diets, including how much soy they ate. Those who said they ate more soy were less likely to have any type of breast cancer, compared to those who ate the least.
That finding doesnât prove that soy prevented breast cancer in any of the women. Other things could be involved.
âMore research still needs to be done,â Meyers says. âIt could be that people who eat more soy have healthier lifestyles in general.â
Stay tuned to see if that proves to be helpful across the board, whether you eat tofu regularly, pour soy milk on your breakfast cereal, or snack on edamame.
Denise Millstine, MD, director of integrative medicine, Mayo Clinic consultant, womenâs health, Mayo Clinic Breast Clinic.
UCSF Medical Center: âA Guide to Foods Rich in Soy.â
Hilakivi-Clarke, L. Journal of Nutrition, December 2010.
Lee, S. American Journal of Clinical Nutrition, June 2009.
Wu, A. British Journal of Cancer, January 2008.
United States Department of Agriculture: âUSDA Database for the Isoflavone Content of Selected Foods.â
Shike, M. Journal of the National Cancer Institute, September 2014.
What Are Soy Foods
Soy is one of the only plant-based food sources of complete protein. Soy is rich in fiber, potassium and magnesium. Examples of soy foods include edamame , tofu, soymilk, soybean sprouts, miso and tempeh . These traditional soy foods have been used in many cultures as reliable sources of protein for thousands of years. More recently, processed soy protein has been added to a variety of foods, such as frozen meals, soups, protein powder drinks, and snack bars.
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