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Debunking the Myths Around Soy

Dispelling the Myth about Soy and Breast Cancer

Is Soy Safe for Women?

“Is soy safe for women?” is a question I hear often. In recent years, the soy debate has intensified, leaving many individuals confused about its potential health benefits and safety of soy for women. As a naturopathic doctor, I frequently encounter concerns about soy, with patients hesitant to incorporate it into their diets due to prevailing myths. This post aims to demystify soy, exploring its safety and the conditions for which it can prove beneficial.

Understanding Soy

As a versatile legume, soy boasts protein, fiber, isoflavones, vitamins, and minerals. Despite its nutritional profile, concerns about phytoestrogens contributing to breast cancer risk have surfaced. Let’s address the burning question: Does soy cause breast cancer?

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Dispelling the Myth about Soy Safety and Breast Cancer

Is soy safe for women? The persistent myth linking soy to breast cancer lacks scientific support. The key lies in understanding a natural compound in soy called isoflavones, a type of phytoestrogen which behaves differently than the estrogen produced by the body. In fact, isoflavones can act as both weak estrogen agonists and antagonists, meaning they can either weakly mimic or block the effects of estrogen, depending on how much estrogen we have naturally. This complexity allows them to have varied effects in different tissues, and can benefit our estrogen hormones when they are too high, or too low.


Clinical Studies and Meta-Analyses

Numerous clinical studies and comprehensive meta-analyses have been conducted to assess the relationship between soy consumption and breast cancer risk. The majority of these studies have found no significant association between soy intake and increased breast cancer risk. In fact studies even suggest a protective effect to breast cancer in pre-menopausal and post-menopausal women (1, 2). 


Hormone Receptor-Positive Breast Cancer

Contrary to belief, recent research indicates that moderate soy consumption is not associated with an increased risk of recurrence in women with hormone receptor-positive breast cancer. Instead, some studies suggest a potential protective effect of breast cancer recurrence (3).

Benefits of Soy Intake

Benefits of Soy for Menopausal Symptoms

Phytoestrogens and Hormone Regulation: One of the key components in soy, isoflavones, belongs to a class of compounds known as phytoestrogens. These compounds have a structure similar to human estrogen and can weakly mimic its effects. In menopause, when estrogen levels decline, soy isoflavones may help modulate hormonal fluctuations and alleviate some menopausal symptoms.

Hot Flashes and Night Sweats: Studies have suggested that soy isoflavones may be particularly beneficial in reducing the frequency and severity of hot flashes and night sweats, common symptoms experienced during menopause (4). By interacting with estrogen receptors, isoflavones may provide a mild estrogenic effect, helping to balance hormonal changes.


Benefits of Soy for Heart Health

Cholesterol Management: Soy has been extensively studied for its potential benefits in managing cholesterol levels, specifically by reducing low-density lipoprotein (LDL) cholesterol, often referred to as “bad” cholesterol. The isoflavones in soy may contribute to this effect by influencing the way the body metabolizes and excretes cholesterol (5).

Blood Pressure Regulation: Some research suggests that soy consumption may contribute to the regulation of blood pressure. Certain bioactive compounds in soy, including peptides and phytochemicals, may have vasodilatory effects, helping to relax blood vessels and reduce blood pressure (6).


Benefits of Soy for Bone Health

Calcium and Vitamin D Content: Soy is a good source of calcium and, in some cases, vitamin D when fortified (such as soy milk). Both of these nutrients are crucial for maintaining strong and healthy bones. Incorporating soy into the diet can be especially beneficial for individuals who may have dietary restrictions limiting their intake of traditional dairy products.

Isoflavones and Bone Density: Some studies suggest that soy isoflavones may play a role in supporting bone health by influencing bone density and reducing the risk of osteoporosis. The estrogenic activity of isoflavones may contribute to the maintenance of bone mineral density, particularly in postmenopausal women who are at an increased risk of bone loss (4).

Soy's Role in Estrogen-Dominant Conditions

Soy’s estrogen-lowering effect holds promise for conditions such as endometriosis, fibroids, PMS, and heavy periods. Acting as a selective estrogen receptor modulator (SERM), soy’s isoflavones may help restore hormonal balance and mitigate the effects of excess estrogen. Additionally, soy’s anti-inflammatory and antioxidant properties contribute to symptom management.

  • SERM Activity: Phytoestrogens, such as isoflavones found in soy, act as selective estrogen receptor modulators (SERMs). SERMs can interact with estrogen receptors, exerting either estrogenic or anti-estrogenic effects depending on the tissue type. In conditions of estrogen dominance, these compounds may help modulate hormonal activity, potentially reducing the impact of excess estrogen. Whereas in someone with low estrogen in menopause, it can help modulate the receptors to have more activity. 
  • Metabolism and Clearance: Soy isoflavones have been studied for their ability to influence estrogen metabolism. They may enhance the activity of enzymes involved in the conversion of estrogen into less potent forms. This can contribute to more efficient estrogen clearance from the body, potentially mitigating the effects of estrogen dominance (7).


Anti-inflammatory and Antioxidant Effects of Soy Foods

  • Inflammation Reduction: Conditions like fibroids and endometriosis are associated with inflammation. Soy’s anti-inflammatory and antioxidant properties help address inflammation, indirectly managing symptoms associated with estrogen dominance.
  • Pain Management in Endometriosis: Soy’s anti-inflammatory effects offer relief for individuals with endometriosis, where chronic inflammation is a contributing factor to pain.

Potential Size Reduction: Some studies have explored the potential of soy isoflavones in reducing the size of uterine fibroids. While research is ongoing, the weak estrogenic activity of soy may compete with the stronger effects of endogenous estrogen on fibroid growth (8).


Pain Management: Soy’s anti-inflammatory effects may offer some relief for individuals with endometriosis, where chronic inflammation is a contributing factor to pain. Additionally, the modulation of estrogen levels may help manage symptoms associated with endometriosis.


PMS and Heavy Menstrual Periods

  • Mood and Symptom Regulation: Phytoestrogens in soy may provide relief from symptoms associated with PMS, including mood swings and breast tenderness. By modulating estrogen levels, soy contributes to more regular and balanced menstrual cycles, potentially reducing the severity of heavy menstrual bleeding (7).

How Much Soy Should You Consume?

To benefit from soy, it is recommended for women to consume a moderate amount which is about 2 servings per day. Here are some examples of serving sizes: 

Edamame: 1/2 to 1 cup

Tofu: 1/2 to 1 cup

Soy Milk: 1 cup

Tempeh: 3 to 4 ounces

Soy Nuts: 1/4 to 1/2 cup

Soy Yogurt: 1 cup

Take Home Message About Soy Safety for Women

Is soy safe for women? The answer: when consumed in moderation and with attention to individual responses, emerges as a valuable addition to a balanced diet. Its potential benefits for heart health, bone health, menopause, and conditions associated with estrogen dominance underscore its versatility. The debunking of the soy-breast cancer myth empowers individuals to make informed dietary choices. As always, consulting with healthcare professionals ensures personalized guidance aligned with individual health needs and goals.


Dr. Elizabeth Miller, a licensed Naturopathic Doctor

Your Doctor: Meet Dr. Miller

Dr. Miller is a Naturopathic Doctor who has a special focus in gut health and women’s health in her practice, and is has extensive knowledge about the interplay of nutrition and specific health conditions.

She completed her doctor or naturopathic medicine degree at the Canadian College of Naturopathic Medicine, and holds a Master’s and Bachelor’s of science in Human Health and Nutrition from the University of Guelph. Her extensive knowledge of nutrition and her strong foundation in scientific research allows for a very thorough approach to your care.

Need nutritional guidance on how to balance your hormones? Learn more about Dr. Miller’s style of practice and our approach to hormonal testing.

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