What are the health benefits of soy?

Posted: Jan 6, 2015

What is soy?

Soy comes from soybean plants. Soybeans are part of the legume family, which includes dried beans, peas and lentils.

Nutritional value of soy


Soybeans are high in quality protein; 175 ml (¾ cup) of cooked soybeans contains as much protein as 75 g (125 ml (½ cup) of cooked meat, chicken or fish. Like meat, soybeans contain all the essential building blocks, or amino acids, in amounts we need for health.
Soy is higher in fat than other legumes, which are generally almost fat-free; however, it’s mainly good fat (monounsaturated and polyunsaturated fats, including omega-3 fatty acids). All legumes, including soy, have no cholesterol.
Soy is an excellent source of the minerals calcium and iron:

  • Calcium builds and maintains strong bones and teeth.
  • Iron is used to carry oxygen to tissue and muscle cells.

Soy also contains isoflavones, which are antioxidants that may have health benefits.

Effects of soy on health

Several national dietary guidelines, including Canada’s Food Guide, recommend soy foods as part of a healthy diet.
The amount of soy needed for health benefits requires more research; however, two to three servings of traditional soy foods a day is thought to be beneficial.
Two to three servings would provide about 15-20 grams of soy protein and approximately 50 to 75 mg of isoflavones. That is an amount that is consitent with an Asian diet.
Soy isoflavone content varies by type of food, type and amount of processing, and by brand. Rich sources of isoflavones are shown in the table.

Soy Food, Isoflavones and Protein

Soy Food Serving Size Protein
Cooked Soybeans
175 ml (3/4 cup)
21 grams
81 mg
Green Soybeans (edamame)
175 ml (3/4 cup)
25 grams
138 mg
175 ml (3/4 cup)
17 grams
52 mg
Roasted Soy Nuts
60 ml (1/4 cup)
11 grams
60 mg
Soy Beverage
250 ml (1 cup)
7 grams
20-30 mg

There has been a lot of research done on the potential  health benefits and safety of soy. The two areas where soy has been found to have beneficial roles are heart health and breast cancer.
Heart health – Replacing high fat animal foods and dairy products with soy foods can be heart healthy. Small decreases  in LDL cholesterol are found by eating at least 20 grams of soy protein daily.
Post-menopausal women may also see a decrease in their blood pressure when soy foods are included in their diets.
Breast cancer –  Soy foods, but not soy supplements, may help to prevent breast cancer. The specific amount of soy needed is not known. More research is needed to better understand the role soy has in breast cancer prevention.
For breast cancer survivors, about 2 servings a day is safe to consume. Soy is a heart healthy food which adds protein, fibre and variety to the diet.

Recent studies now show that women who have had estrogen-sensitive breast cancers do not need to avoid soy isoflavones. It remains important that any woman who has had breast cancer should talk to her doctor about eating soy foods.

Common Soy Foods

There are many kinds of soy foods made from soybeans.  Choose less processed traditional soy foods, such as tofu, soybeans and soy beverage:
Tofu – Use firm or extra-firm tofu in vegetable stir-fries, soups and pasta sauces. Silken tofu is good for preparing smooth sauces, dips, creamy desserts, shakes or soups.
Soybeans – Whole soybeans can be found fresh, dried, canned or roasted. Dried, canned or green soybeans can be added to salads, soups or pasta dishes. Green soybeans (edamame) can also be found frozen; they can be steamed or boiled and eaten as a vegetable.
Soybeans can also be soaked in water then roasted in oil or using dry heat. Roasted soybeans, or soy nuts, taste similar to peanuts and are sold plain, salted or seasoned. They are a nice alternative to peanuts and contain less fat.
Soy beverages – Soy beverages are ground-up soybeans made into a liquid that looks like milk. You can drink a soy beverage ‘as is’, or you can use it to replace cow’s milk in tea, pour it into a bowl of cereal or even use it for cooking sauces and soups.
Be sure to choose a plain fortified soy beverage that has at least 7 grams of protein per 250 mL (1 cup). Fortified soy beverages have just as much calcium, vitamin D, A and zinc as milk.
Soy beverages also provide an average of 8 to 14% of the recommended daily iron intake.