Diane May Nutrition Blog

The Truth About Soy

July 27th, 2014

There are so many conflicting reports about soy that it can be very confusing.  Common thoughts are that soy can help with menopause symptoms, reduce the risk of prostate and breast cancer, lower cholesterol, expedite weight loss and hold osteoporosis at bay.  Soybeans are a legume  high in isoflavones (a plant based estrogen), saponins, phenolic acid, phytic acid, enzymes and sphingolipids. Almost all soy in this country, including organic soy, is genetically modified. Soybeans are considered a complete protein.  This means that they contain all the amino acids the body needs. One serving (1 cup) of cooked soybeans contain 22 grams of protein.  But not all soy is created equal.  A 3 ounce serving of extra firm tofu contains only 9 grams of protein. Many people who do not enjoy soy have been taking soy isoflavone supplements.  Although safe in the short term, there is no evidence that taking these supplements long term is safe. So what about all the health claims associated with soy?

Symptoms of menopause: The theory is that the plant based estrogen (phytoestrogen) found in soy can alleviate the flagging estrogen and concurrent symptoms such as hot flashes during menopause. As shown in a study published in the journal Obstetrics and Gynecology, There is no strong evidence that soy or soy isoflavones reduce the symptoms associated with menopause.

Prostate and breast cancer: There has been positive research that consumption of isoflavones can reduce PSA levels.  It is important to note that research is mixed and most studies did not specify if the prostate cancers studied were hormone driven tumors or not.  There is very mixed evidence to support soy’s benefits related to breast cancer.  There appears to be a significant benefit to consumption of soy and breast cancer prevention when consumption starts in adolescence.  These studies were done on Asian women, and as of now,  have not been studied in conjunction with a western diet. There have also been studies suggesting that concentrated dosages of soy can stimulate breast cancer cells. If you are going to consume soy once you have these cancers, consult with your physician and do so in moderation.

Cholesterol reduction: In a study published in the New England Journal of Medicine, consumption of soy protein rather than animal protein significantly decreased serum concentrations of total cholesterol, LDL cholesterol, and triglycerides without significantly affecting serum HDL cholesterol concentrations. Reducing animal protein at least one day a week and switching to any plant based protein can have a positive impact on cholesterol levels.

Weight loss: There is no solid evidence that soy increases weight loss.  The Journal of the American Dietetic Association concluded that consumption of soy is not a functional food for weight loss.  The best way to lose weight is to eat lots of vegetables, fruit, whole grains, lean protein, low fat/non fat dairy and drink lots of water.

Osteoporosis prevention: Although not harmful, there is no evidence that consumption of isoflavone rich foods can prevent bone loss.  The best way to prevent bone loss is to exercise regularly (making sure to include weight bearing activities), get enough calcium and vitamin D, and in some cases, taking bone-strengthening drugs such as bisphosphonates (if already osteoporotic).

If you enjoy soy, there is no reason not to consume it, just in moderation.  Many of the claims touting significant health benefits are clearly not accurate. More research is needed to understand the true impact of soy as it relates to health. The American Cancer Society as well as other organizations do not recommend the usage of soy supplements as they have no known benefit.


Vietnamese Lettuce Rolls with Spicy Grilled Tofu



  • 1 (16-ounce) package water-packed firm tofu, drained
  • 1/2 cup fresh lime juice $
  • 1/2 cup honey
  • 1/4 cup thinly sliced peeled fresh lemongrass
  • 2 tablespoons low-sodium soy sauce
  • 3/4 teaspoon chile paste with garlic
  • 1/4 teaspoon freshly ground black pepper
  • 3 garlic cloves, minced
  • Cooking spray $
  • 1 head romaine lettuce $
  • 1/2 cup cilantro leaves $
  • 3 tablespoons chopped dry-roasted peanuts $
  • 36 small mint leaves $
  • 36 (2-inch) strips julienne-cut carrot $
  • 12 basil leaves $


  1. Cut tofu crosswise into 12 (1/2-inch) slices. Place tofu slices on several layers of heavy-duty paper towels. Cover tofu with additional paper towels. Place a cutting board on top of tofu; place a cast-iron skillet on top of cutting board. Let stand 30 minutes to 1 hour. (Tofu is ready when a slice bends easily without tearing or crumbling.) Arrange tofu in a single layer in a 13 x 9-inch baking dish.
  2. Combine juice and the next 6 ingredients (juice through garlic) in a small saucepan, and bring to a boil. Cook 1 minute, stirring until honey dissolves. Pour over tofu. Cover and let stand at room temperature 1 hour.
  3. Prepare grill.
  4. Remove tofu from dish, and reserve marinade. Coat tofu with cooking spray. Place tofu on grill rack coated with cooking spray. Grill 3 minutes on each side or until browned.
  5. Remove 12 large outer leaves from lettuce head; reserve remaining lettuce for another use. Remove bottom half of each lettuce leaf; reserve for another use. Place 1 tofu slice on each lettuce leaf top. Top each leaf top with 2 teaspoons cilantro, 3/4 teaspoon peanuts, 3 mint leaves, 3 carrot strips, and 1 basil leaf. Wrap leaf around toppings. Serve with reserved marinade.

Cooking Light
JUNE 2003

Nutritional Information

Amount per serving

  • Calories: 294
  • Calories from fat: 29%
  • Fat: 9.5g
  • Saturated fat: 1.5g
  • Monounsaturated fat: 2.5g
  • Polyunsaturated fat: 4.9g
  • Protein: 14.8g
  • Carbohydrate: 44.9g

Vietnamese lettuce wrap