Soy Protein and Soy Isoflavones

Soy is one of the most versatile foods available, as well as one of the most researched in terms of its potential health benefits. To have a better understanding of this common food and ingredient, let's look at what we know at this time.

Nutrition Information

Soybeans are a legume, meaning their seeds grow in enclosed pods. What makes them unique from other legumes is their high protein, healthy fat and fiber content, and lower carbohydrate content. Additionally, soy is a complete plant protein containing all of the essential amino acids our bodies need.

Foods made from soy include tofu, edamame (fresh soy beans), miso (a traditional Japanese seasoning made of a thick soy-based paste used in sauces, spreads, pickling, and soups), and tempeh (a cooked and slightly fermented soybean patty). Some are made with soybean extracts: soy isolate, soy protein concentrate, soy protein flours, soy milk, soy yogurt, soy-based infant formula and gluten-free breads. Meat alternatives like soy vegetable burgers are good substitutes for meat, poultry, and other animal-based foods because of their high quality protein. 

Tip: Excellent sources of soy protein include soy milk, tofu, tempeh, miso, and edamame. Give them a try! 

The fat in soybeans are primarily polyunsaturated and monounsaturated fats, which are the heart-healthy fats. Soybeans are one of the few plant foods that provide the omega-6 (linoleic) and omega-3 (alpha-linolenic) acids, both essential fatty acids.

Nutritionally, soy is a good source of fiber, B vitamins, calcium, iron, and other vitamins and minerals. Soy isoflavones are special substances found in soybeans that work in combination with the soy protein, possibly providing additional health benefits. The two main isoflavones in soybeans, genistein and daidzein, have weak estrogen-like effects.

Ways to Add Soy

If you are not familiar with soy products, you may want to start by experimenting with some of the snack foods or combining soy products with regular products, such as making a vegetable dip with half-silken tofu and half-regular sour cream. In recipes with meat, start by replacing some of the meat with tofu or soy crumbles. In lasagna, use half ricotta cheese and half pureed tofu or soy cheese. Just be aware that soy products will have different textures and culinary characteristics than the foods you are used to eating, so start slowly.

Health Benefits

The 2015–2020 Dietary Guidelines for Americans notes that “a healthy eating pattern can include a variety of soy food products." The research on soy, soy protein, and soy isoflavones supports the safety of soy's consumption and its positive health impacts. 

When it comes to heart health, soy protein is beneficial in lowering LDL cholesterol without an unfavorable effect on HDL cholesterol or triglycerides.

Recent research suggests that consumption of soy may have a more moderate effect in lowering blood cholesterol than previously believed. As a result, the U.S. Food and Drug Administration is proposing a removal of the authorized health claim stating that “consuming 25 grams of soy protein a day may reduce the risk for heart disease." The proposal still allows for a qualified health claim on the label of products containing soy, which simply means that the evidence is not as strong as necessary to make the previous statement. For those with high blood pressure, consumption of soy protein and soy isoflavones can help lower blood pressure. It is not clear whether this is due to the soy compounds themselves or the fact that these foods replace foods that are high in saturated fat and cholesterol. 

Other areas of research indicate that soy isoflavones help with bone mineral density in postmenopausal women. The components in soy (fiber, isoflavones, protein, and oligosaccharides) may help increase the amount of beneficial bacteria that make up the gut microbiome. Diets containing soy may also protect against colorectal, prostate, and endometrial cancers. In regard to breast cancer, new research indicates that consuming soy may actually lower breast cancer risk, whereas at one time it was thought to increase risk. Research is ongoing in all of these areas, and it is always best to discuss your personal health situation with your medical provider.

Shopping Tips

There is a wide array of fresh, canned, dried, and frozen soy-based products at the grocery store.

Dairy aisle

Most dairy products are now available with soy as a base, including milk, cheese, yogurt, and sour cream. Some dairy foods may have added soy protein to boost their protein content, so be sure to read the ingredient list. 

Eggs

Soy egg replacers 

Freezer case

Edamame, soy bacon, soy burgers, soy crumbles (ground meat substitute), soy entrees, soy-based ice cream 

Grocery aisle

Canned black and yellow soybeans, dried soybeans, miso, seasoning mixes with soy, soy cereal, soy flour, soy jerky, soy nut butter, textured soy protein (TSP), soy beverage powders 

Meat counter

Garden or soy burgers, soy hot dogs

Produce

Edamame (in pod or shelled), soy sprouts, tempeh, tofu

Snack aisle

Soy protein bars, soy nut trail mix, soy nuts