By Sue Delagrange, Registered Dietitian
What is the difference between Estrogen (naturally produced in humans) and Plant Phytoestrogens (Isoflavones) which are naturally found in soy products?
Estrogen is referred to as the female sex hormone. It is primarily produced by the ovaries and travels in the bloodstream to interact with tissues. Estrogen is crucial to the reproductive function of women. Other functions include helping to preserve bone strength and improving the thickness and quality of the skin.
Isoflavones are naturally occurring compounds widely found within the plant kingdom, especially in legumes such as soybeans. Soybeans and most foods made from soybeans are uniquely rich sources of isoflavones. Isoflavones serve two roles in plants. They are a defense mechanism, that is, they help ward off disease in the plant. And in addition, isoflavones pull nitrogen from the soil to help the plant produce compounds that it needs to survive such as amino acids.
Isoflavones have been rigorously studied by health scientists over the past 30 years when the U.S. National Cancer Institute first expressed interest in understanding the role of isoflavones in cancer prevention and treatment.
Soy is exalted as a health food by some, with claims of taming hot flashes, warding off osteoporosis, and protecting against hormonal cancers like breast and prostate.
At the same time, soy is shunned by others for fear that it may cause breast cancer, thyroid problems, and dementia, though these claims have not been substantiated.
Should I Consume Soy?
Studies may seem to present conflicting conclusions about soy, but this is largely due to the wide variation in how soy is studied. Results of recent population studies suggest that soy has either a beneficial or neutral effect on various health conditions. Soy is a nutrient-dense source of protein that can safely be consumed several times a week, and probably more often, and is likely to provide health benefits, especially when eaten as an alternative to red and processed meats.
Aside from their isoflavone content, soy foods are rich in nutrients including B-vitamins, fiber, potassium, magnesium, and high-quality protein. Unlike some plant proteins, soy protein is considered a complete protein, containing all nine essential amino acids that the body cannot make which must be obtained from the diet.
Research on Soy and Disease
Heart Disease – Soy has shown potential benefit in lowering cholesterol levels. A 1995 meta-analysis of thirty-eight controlled clinical trials showed that eating approximately 50g. of soy protein a day (ex. 1 ½ pounds of tofu), in place of animal protein reduced harmful LDL cholesterol by 12.9%. (ref. New England Journal of Medicine. 1995 Aug).
Breast Cancer– Overall, the effect of soy consumption on breast cancer risk seems to be highly beneficial. A huge 2003 study published in the Journal of the National Cancer Institute, found that women with a high intake of soy (in the form of miso soup) reduced their risk of breast cancer by 54% compared to women with a low intake of soy. Although soy consumption, overall, reduces cancer incidence, there are questions about the effect on women who have estrogen-positive (ER+) breast tumors. These tumors are stimulated by estrogen. More research needs to be done to determine if ER+ breast tumors are stimulated by the weak estrogenic activity of the isoflavones found in soy.
Most experts, however, align with the Oncology Practice Group of the Academy of Nutrition and Dietetics, which tells us: “The current consensus among health experts who study soy is that breast cancer survivors can safely eat these foods. Emerging research suggests that soy foods may decrease the likelihood of breast cancer recurrence in women with a history of the disease.” (ref. https://www.oncologynutrition.org)
Prostate Cancer – The incidence of prostate cancer is greater in Western countries and lower in Asian countries, where soy foods are regularly eaten. In addition, observational studies have found an increased risk of prostate cancer in Chinese and Japanese men who move to Western countries and adopt a Western diet, but not in those who continue eating a traditional Asian diet. Soy isoflavones, specifically genistein and daidzein, are incorporated in prostate tissue and may function as weak estrogens and inhibit the development of prostate cancer. (ref: Nutrients. 2018 Jan).
Types of Soy Products:
What are the diverse types of soy you can enjoy? Whole soy foods such as tofu, soybeans, soy milk, and soy nuts are preferred sources. Soy protein powders and soy-based veggie burgers should be limited due to being highly processed.
The following is a list of foods containing soy.
Edamame
These soybeans are harvested when the beans are still green and sweet tasting. They can be served as a snack or a main vegetable, after boiling in slightly salted water for 15 to 20 minutes. They are high in protein and fiber and contain no cholesterol. Edamame can be bought shelled or in the pod in the supermarket produce section or frozen food aisle.
Miso
Miso is a rich, salty soy paste used in Japanese cooking. The Japanese make soup and use the miso to flavor a variety of foods such as sauces, dressings, and marinades.
Soymilk
Soybeans that are soaked, ground fine and strained produce fluid called soybean milk. Plain, unfortified soymilk is an excellent source of high-quality protein and B vitamins, but lacks calcium and vitamin D. Fortified versions, however, are available.
Tempeh
Tempeh is a chunky, tender soybean product. Whole soybeans, sometimes mixed with another grain such as rice or millet, are fermented and pressed into a cake or bar with a smoky or nutty flavor. It can be sliced, marinated, grilled, and added to soups, casseroles, or chili.
Textured soy protein
Textured soy protein (TSP) refers to products made from textured soy flour, textured soy protein concentrates and spun soy flour. Textured soy flour contains about 70 percent protein and retains most of the bean’s dietary fiber. Textured soy flour is sold dried in granular and chunk style. When hydrated, it has a chewy texture. It is widely used as a meat extender. One of the most popular brands is called Textured Vegetable Protein (TVP).
Tofu
Tofu, also known as soybean curd, is a soft, smooth soy product made by curdling fresh, hot soymilk with a coagulant. Tofu has a mild flavor and easily absorbs the flavors of marinades, spices, and other ingredients. Tofu is rich in high-quality protein and B vitamins, and low in sodium. There are two main types of tofu:
Water packed tofu comes in extra-firm, firm, and soft varieties. This tofu is dense and solid and holds up well in stir fry dishes, soups, on the grill or anywhere you want tofu to maintain its shape.
Silken tofu comes in extra-firm, soft, and reduced-fat varieties. This tofu is made by a slightly different process that results in a softer product. Silken tofu works well in pureed and blended dishes.
Here are a few recipes you should try!
Garlic Teriyaki Edamame (serves 4)
Recipe and photo from AllRecipes | For a printable recipe, click here
Ingredients
- ¼ cup water
- 3 cloves garlic, minced
- 1 (16 ounce) package frozen edamame in the pod
- ½ cup teriyaki sauce
- ¾ teaspoon salt
- 2 tablespoons brown sugar
- 2 tablespoons rice vinegar
- 1 tablespoon sesame oil
- 2 tablespoons sesame seeds
Instructions
- Bring water and garlic to a boil in a saucepan over high heat. Stir in edamame; cook until edamame is hot, and liquid has nearly evaporated, about 5 minutes.
- Reduce heat to medium-high and stir in teriyaki sauce, salt, brown sugar, rice vinegar, and sesame oil. Stir constantly until sauce has thickened and coats edamame, about 4 minutes. Sprinkle with sesame seeds to serve.
Nutrition Facts: 261 Calories, Total Fat 12g; Saturated Fat 2g; Sodium 707mg, Carbohydrate 23g, Fiber 5g, Protein 15g.
Mushroom & Tofu Stir-Fry (serves 5)
Recipe and photo from Eating Well | For a printable recipe, click here
Ingredients
- 4 tablespoons peanut oil, divided
- 1-pound mixed mushrooms, sliced
- 1 medium red bell pepper, diced
- 1 bunch scallions, trimmed and cut into 2-inch pieces
- 1 tablespoon grated fresh ginger
- 1 large clove garlic, grated
- 1 (8 ounce) container baked tofu or smoked tofu, diced
- 3 tablespoons oyster sauce or vegetarian oyster sauce
Instructions
- Heat 2 tablespoons oil in a large flat-bottom wok or cast-iron skillet over high heat. Add mushrooms and bell pepper; cook, stirring occasionally, until soft, about 4 minutes. Stir in scallions, ginger, and garlic; cook for 30 seconds more. Transfer the vegetables to a bowl.
- Add the remaining 2 tablespoons oil and tofu to the pan. Cook, turning once, until browned, 3 to 4 minutes. Stir in the vegetables and oyster sauce. Cook, stirring, until hot, about 1 minute. Serve with steamed white or brown rice.
Nutrition Facts: Per 1 ¼ cup serving (excluding rice): 171 Calories, Total Fat 13g; Saturated Fat 2g; Sodium 308mg, Carbohydrate 9g, Fiber 2g, Protein 8g.
Tempeh Tacos (serves 4)
Recipe and photo from Well Plated | For printable recipe, click here
Ingredients
- ¼ cup water
- 1 medium lime, zest, and juice (about 2 tablespoons juice and ¾ teaspoon zest)
- 1 tablespoon pure maple syrup
- 2 ½ tablespoons ground chili powder
- 2 teaspoons liquid smoke optional – if not using consider adding ½ teaspoons chipotle chili powder which is spicy and smoky
- 2 teaspoons smoked paprika
- 1 teaspoon ground cumin
- 1 teaspoon garlic powder
- 1 teaspoon onion powder
- 1 small, sweet potato scrubbed
- 1 tablespoon extra-virgin olive oil
- 8 ounces tempeh (ex. Lightlife Original)
- 3 tablespoons low sodium soy sauce
- Corn or flour tortillas
- Toppings: diced avocado, thinly sliced jalapeno, chopped fresh cilantro, salsa
Instructions
- In a small mixing bowl or larger liquid measuring cup, whisk together the water, lime zest, lime juice, maple syrup, chili powder, liquid smoke, smoked paprika, cumin, garlic powder, and onion powder. Set it aside.
- With a box grater, or the shredding blade of a food processor, shred the sweet potato (no need to peel it). You should have about 2 heaping cups. Set it aside.
- Heat the oil in a large nonstick skillet over medium heat. Break the tempeh into small pieces. Cook, continuing to break it up, for 2 minutes until just turning golden. Fold in the sweet potato and continue to cook until it begins to soften, about 4 minutes more.
- While the sweet potato cooks, warm the tortillas, by spreading them on a baking sheet and warm in a 300-degree oven for a few minutes.
- Add the sauce to the tempeh and sweet potato mixture. Let it cook until the sauce has thickened slightly, about 3 more minutes. Taste and adjust seasoning as desired. Pile this mixture inside the warm tortillas, add any and all toppings, and enjoy!
Nutrition Facts: Per 1 serving: 234 Calories, Total Fat 11g; Saturated Fat 2g; Carbohydrate 26g, Fiber 4g, Protein 13g.
