The question of whether soy foods can be consumed safely by breast cancer survivors has perplexed not only patients but even health professionals over the years.  There was often confusion on what to advise breast cancer survivors on what to do.  Now we have evidence that people’s fears of soy foods raising the risk of hormone-related cancers are unwarranted and soy can safely be consumed.

Where the confusion over soy began

What started the confusion were previous studies of soy intake by rodents with breast cancer growth.  These studies suggested a phytochemical in soy called genistein, increased the growth of estrogen receptor-positive (ER+) breast cancer cells thus promoting breast cancer growth.  The fear was that soy foods – which contain phytoestrogens or plant estrogens – would mimic human estrogen and would fuel estrogen related cancers.  However, thanks to major population studies on humans, it was determined that rats and mice metabolized genistein differently leading to a higher blood level of genistein in an active form than what it is in humans. Plants do not and cannot grow human estrogen. 

Clinical studies on humans have found no adverse effect of soy on mammographic density, estrogen levels or breast cell proliferation.  These same studies have shown that moderate intake of soy foods does not increase a woman’s risk of death or recurrence, including women with ER+ breast cancer and some studies even had better outcomes when soy foods were consumed regularly.

Foods containing soy and what is a safe amount to consume

Soy comes from soybeans, a legume similar in size to a pea.  Many foods contain soy and the best advice is to choose soy in its most unprocessed form.  Avoid processed alternative soy foods such as soy bacon, “chicken-less” nuggets, corn dogs, hamburgers, hot dogs and ice cream made with soy.  If you read “soy protein isolate” in the ingredient list, this is processed soy and will lack some fiber, vitamins and minerals than what is found in unprocessed soy. 

Eat food sources of soy and not supplements – our body prefers nutrients in food not pills.  Choose moderate amounts – one to two servings a day – of minimally processed soy foods such as:

·         Edamame – ½ cup

·         Tofu – 3 ounces

·         Miso – it is high in sodium

·         Soymilk – 1 cup

·         Soy nuts – ¼ cup

·         Tempeh – 3 ounces

·         Whole soybeans – ¼ cup

·         Soy nut butter – 2 tbsp.

Reasons why soy is safe to consume

1.      Contains a variety of phytochemicals.  Phytochemicals – phyto means plant – are substances in plants that have health-protective effects in the human body.  Soy contains the following phytochemicals:

·         Isoflavones – this includes genistein, daidzein and glycitein.  Isoflavones may help breast cancer by reducing effects of human estrogen and prevent prostate cancer by hindering cell growth.

·         Saponins – these may lower blood cholesterol and protect against cancer

·         Phenolic Acids – May stop cancer cells from spreading

·         Phytic Acid – acts as an antioxidant

·         Sphingolipids – help regulate cell growth, self-destruction of abnormal cells and progression of tumors

2.      Soy is a good source of many key nutrients.  Soy is an excellent high-quality, complete source of protein and is the only plant source of protein that contains all nine of the essential amino acids like animal sources do.  It also is a good source of fiber, manganese, magnesium, calcium, potassium, iron and copper.

3.      Soy is a healthy alternative to red and processed meat.  Red meat (beef, pork and lamb) and processed meat (hot dogs, sausage, bacon, luncheon, salami) have been linked to increasing colorectal cancer.  Soy is low in saturated fat, is cholesterol free and contains heart healthy fats.  

4.      Soy can be used by people with lactose intolerance or a milk allergy.  Soymilk is made when soybeans are soaked in water, ground up and strained.  Depending on the brand of soymilk, it has a comparable nutritional value to cow’s milk with one cup containing 8 grams of protein, 5 grams of fat and anywhere from 80-170 calories.  Unlike cow’s milk, soymilk has 10 percent of the daily value for fiber and contains omega-3 fatty acids which help reduce lipid levels. 

5.      Soy may have cardiovascular health benefits.  Even though studies have shown soy’s ability to lower LDL or “bad” cholesterol is small – at the same time soybeans are cholesterol free and are a good source of fiber both of which are beneficial to decreasing heart disease.

6.      Soy and calcium-fortified soy foods are good for bone health.  Soy contains the phytochemical isoflavone along with calcium and vitamin K, all of which promote strong bones.  Several studies have shown isoflavones in soy to increase bone mineral density in postmenopausal women. 

7.      Soyfoods may help relieve the menopausal symptom of hot flashes.  This was based on research that showed Japanese and Chinese women, who consume more soy foods, had much lower frequency of hot flashes than American women.  In 2006, a meta-analysis showed that soy isoflavones significantly reduced the number of hot flashes a woman experienced which was dependent on the dose of soy isoflavone provided. 

Anyone who is a cancer survivor should always consult with their physician on the safety of foods such as soy.  For more information on soy foods and products and the health benefits they offer, visit www.soyconnection.com,  www.soyfoods.org or www.thefactsaboutsoy.com.

ABOUT CHERYL MUSSATTO, REGISTERED DIETITIAN

Cheryl Mussatto has over 30 years of experience as a Registered Dietitian and has worked in a variety of settings that cover a wide span of nutrition experience.  Currently she works as an adjunct professor for two community colleges, Allen Community College in Burlingame and Butler Community College in Council Grove, Kansas teaching two courses, Basic Nutrition and Therapeutic Nutrition. Cheryl also is a contributing author for osagecountyonline.com, an online newspaper and Edietitians, a global free nutritional and health magazine. Her articles for both publications pertain to nutrition topics that cover a diversity of health and nutrition interests for the general public.  She is also certified as a health and wellness coach.