Soy protein is considered one of the “complete proteins” since it contains all the essential amino acids our bodies need and is also low in saturated fat. It is also one of the least expensive sources of dietary protein.
The downside: Soy is plant-based and the molecular structure is not as similar to human proteins as animal based proteins such as whey protein. Soy can be more difficult for the human body to digest and frequently can cause gas and bloating. It doesn’t deliver its benefits as rapidly to the body as whey protein. It’s simply not as easy for our bodies to digest it as an animal-based protein. Soy isolate is the most pure form of this plant protein and is the easiest type for the body to digest. It is also commonly used by vegetarians as an alternative to consuming meat for their protein, although many vegetarians also consume whey protein.
The protein in soy is extracted from the soybean, so is therefore a plant-based protein. Soybeans are processed into three different kinds of protein: concentrates, isolates and soy flour. It is used in a variety of foods such as soups, cheeses, whipped topping, infant formula, salad dressings, breakfast cereals, pasta, pet food and more. A report released in 1995 estimated that over 12,000 food products were available that contained soy (Anderson, Johnstone, & Cook-Newell, 1995).
There have been conflicting studies regarding the health effects of soy; some suggest an increased cancer risk, while others suggest a decreased risk of some cancers. This plant protein contains phytoestrogens, which bind to estrogen receptors in the body. There are also conflicting studies as to whether the estrogenic compounds such as genistein and daidzein caused increased levels of estrogen in men and decreased testosterone levels. Soy also contains phytic acid, a compound that may interact with mineral absorption.
Soy isolate is the most common soy supplement, and it is derived from defatted soy flour as is the most purified form of this plant protein. It is frequently an ingredient in soy protein drinks.
Soy protein concentrate is about 70% soy protein and retains most of the fiber of the original soybean.
Soy Flour is the ground up soybean which comes in three different kinds:
Soy contains Saponins which support healthy immune system function and combine with cholesterol to reduce its absorption through the small intestines. Soy also contains Phytosterols which also help to maintain healthy cholesterol levels.
Although there are some benefits to soy, I personally recommend staying away from it and concentrating on animal based protein supplements such as whey protein and egg protein which are far more absorbable in the body and have less waste.