Vegetarians and those with other dietary restrictions may find meal planning a challenge, especially when it comes to getting enough protein in their daily meals. If you eat a wide variety of plant-based foods, you'll ultimately get the protein you need, says the Harvard School of Public Health. Soy stands apart from the others as the most complete source of vegetable protein.
Complete vs. Incomplete Proteins
Proteins are made up of building blocks called amino acids, of which there are 20, explains the Centers for Disease Control and Prevention. When your body needs to repair itself, it can produce certain amino acids on its own, while others need to be supplied through your daily diet. A complete source of protein has all of the essential amino acids you need for a healthy body. Animal-based foods such as meat, dairy products and eggs are complete, or high-quality, proteins. Incomplete proteins are those that lack one or more essential amino acid. Vegetable proteins such as beans, nuts and grains fall into this category.
The Soy Exception
Soy foods are the sole exception in the vegetable protein category, providing all essential amino acids -- a complete protein source -- along with low saturated fat and low cholesterol. Citing the American Heart Association, the Harvard School of Public Health states that while soy doesn't directly affect your cholesterol, replacing animal foods with soy foods can. Eating soy as a meat substitute also makes for a healthier heart and blood vessels and provides extra vitamins, minerals and fiber. Research indicates that replacing animal protein with 50 g of soy protein reduces total cholesterol levels. Over a long period of time, this diet could reduce your risk of heart attack, stroke and cardiovascular disease by 20 percent.
About Soy
Foods made from the protein-packed soybean, or edamame, have been consumed for about 5,000 years, says the University of Maryland Medical Center, or UMMC. Soy foods are a staple in Japanese and Chinese cuisine, and they're becoming increasingly popular in the U.S. Soybeans can be made into any number of food types, such as soft and firm tofus, soy milk, soy butter, soy cheese, soy nuts, soy oil, miso and tempeh. According to the UMMC, tofu and soy milk are the richest sources of vegetable protein.
Soy Safety
Unless you're allergic to soy foods, the UMMC indicates that no side effects have been reported by people who eat soy-based foods. Soy does, however, contain plant-based estrogens called isoflavones, which may not be appropriate for all populations. Soy may not be an ideal food choice for women who've had breast cancer, as it may stimulate the growth of cancer cells, although more research on this area is needed, says the UMMC. The phosphorus and potassium in soy foods also make soy a questionable choice for people with kidney disease. Very rarely, cases of hypothyroidism have occurred in infants who were fed soy formula, as isoflavones decrease the level of iodine in the body.
Other Health Benefits
According to the National Center for Complementary and Alternative Medicine, research not only supports soy protein for lowering "bad" cholesterol levels but also suggests that it may reduce hot flashes in post-menopausal women because of its isoflavones. There's still not enough research, however, to determine conclusively whether soy has other health benefits. The Harvard School of Public Health supports soy foods as an alternative to red meat but encourages you not to make it a sole protein source. It recommends that you aim for two to four servings of soy foods each week but avoid supplements that contain soy protein or soy isoflavones, since their benefits have not been established.
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