Soy protein is a purely vegetable protein produced from soybeans. Even though vegetable proteins generally have the reputation of having a lower biological value compared to animal proteins, this does not apply to soy protein. Soy protein is a so-called complete protein, which contains all the essential amino acids for humans. Of all vegetable proteins, soy protein has one of the highest biological values with a value of 84 and is thus almost on a par with milk protein, which has a biological value of 86.
Even though there is a persistent rumor in bodybuilder circles that soy protein contains large amounts of phytoestrogens, which supposedly cause estrogen-related side effects and lower testosterone levels, this is nothing more than a modern fairy tale. There are no studies in the scientific literature to suggest that such a thing could occur in humans.
Soybeans have a high content of oils and proteins. The latter contain very many high-quality essential amino acids, including glutamine, arginine, lysine, leucine and isoleucine. Soy proteins are comparable in quality to animal proteins, they are therefore used for the production of "artificial meat". Soybean oils are used for the production of margarines. Other components of soybeans are used for the production of flours, milk, yogurt and curd, among others. Young soybean seedlings can also be eaten as sprouted vegetables. Soybeans contain fats (including 55% essential linoleic acid), proteins, and carbohydrates, as well as a number of other nutrients. These include lecithin, some vitamins (B2 and E) and minerals (cobalt), saponins, isoflavonoids, choline and betaine.
What are the benefits of soy protein?
- Suitable for vegetarians and vegans
- Has one of the highest biological value of all vegetable proteins
- Provides a purely plant-based alternative to whey protein before and after workouts due to its fast digestion rate
- Free from lactose and also suitable for people suffering from lactose intolerance
- Has numerous additional health benefits
Soy protein has some characteristics that other proteins do not offer:
- The glutamine content is 19%, almost as high as that of casein and significantly higher than that of whey.
- Soy protein, unlike other proteins, can help raise thyroid hormone levels, which is helpful for bodybuilders on a diet. In the process, there is also often an improvement in blood lipid levels.
- One of the isoflavones in soy, called daidzein, has been shown to increase testosterone and growth hormone levels in male experimental animals. There was also less muscle mass loss during dieting compared to casein.
Soybeans (Glycine max) belong to the legume family and are originally native to East Asia as well as Africa and Australia. The Chinese were already cultivating the soybean plant around 3,000 years ago, but it was not until the 19th century that it was also introduced to America and Europe. Today, soy is cultivated worldwide, with the USA accounting for more than half of global production. Soy plants are mainly used as animal feed, and their seeds, the soybeans, can be used in a variety of ways for human nutrition. Soy has long been regarded in Asia not only as a nutritional crop, but the health effects of soy have also been known for thousands of years. In China, soy has traditionally been used to treat colds, skin diseases, diarrhea, constipation, anemia and leg ulcers, among others.
Soy protein, like Whey protein, belongs to the fast digestible protein sources, which already 30 to 45 minutes after consumption cause a significant increase in amino acid levels in the blood and quickly supply your body and your muscles with important protein building blocks. Furthermore, soy protein is easily digestible and well tolerated, so that it does not particularly burden the digestive system and can therefore also be consumed shortly before training.
Soy protein contains so-called phytosterols, which can lower cholesterol levels, which may have positive effects on cardiovascular health. Furthermore, soy protein contains isoflavones, which act as antiestrogens in the human body and can reduce the risk of cancer and other diseases. In addition, soy protein can counteract bone loss due to osteoporosis, thereby promoting bone stability and health.
Soy protein is particularly well suited as a protein source for vegetarians and vegans, as it has the highest biological value of all plant proteins. But soy protein also enjoys great popularity among many non-vegetarians, which is not only related to the above-mentioned health benefits. Since soy protein does not naturally contain lactose, unlike protein supplements made from dairy products such as whey protein and casein, it is an excellent alternative for all athletes who suffer from lactose intolerance. As the above-mentioned fast digestibility already suggests, soy protein is very suitable for use before, during and directly after training. Also in the morning, when your body's amino acid levels have reached a low point after an overnight fast, a fast digesting protein like soy protein is a good choice, as it is able to quickly restore blood amino acid levels. Of course, you can also use soy protein at any other time of day to meet your protein needs.
People from Asian countries consume about 15 to 40 mg of soy per day with their traditional diet. In our country, soy products are used rather rarely, so we usually consume less than 2 mg daily. Soy may promote cardiovascular and cancer protection. It helps lower total cholesterol and LDL cholesterol as well as triglycerides. Especially in cases of elevated cholesterol levels, replacing animal proteins with soy proteins may have a cholesterol-lowering effect. Presumably, soy can also help lower blood pressure and reduce the peroxidation of lipoproteins. In the USA, therefore, foods containing soy protein are now allowed to carry the claim that their consumption helps prevent heart disease. With its anti-carcinogenic effects, soy can specifically prevent breast, prostate and uterine cancer. It is known from Asian countries that hormone-dependent cancers (breast and prostate cancers) occur much less frequently. This may be due to the abundant consumption of soy products. Soy may also increase bone density and in this way help protect against osteoporosis. For menopausal women, some of the typical symptoms may be alleviated. Soy proteins can lower hematocrit (percentage of red blood cells) and reduce blood thickness. They can facilitate weight loss in reduction diets and promote muscle growth.
Isoflavonoids - the most important phytamins in soybeans
Isoflavonoids belong to the group of bioflavonoids and are also found in other plants, but soy is the richest source of these phytamines. Isoflavonoids have antioxidant and anticarcinogenic effects, each acting in a similar way on different types of cancer. What they all have in common is a structure similar to estrogens, but with much weaker effects. Isoflavonoids are therefore often referred to as phytoestrogens. Isoflavonoids are distributed differently in the soybean, with the highest amounts located in the seed coats. Some soy products, e.g. soy sauces and soy oils, do not contain these phytamines.
Genistein is the most important isoflavonoid in soy and is water soluble. Of all the isoflavonoids, genistein has been the best studied to date. It may have estrogenic effects, but may also prevent undesirable estrogenic effects in the body and thus contribute to protection against breast cancer, for example. Genistein can inhibit processes within cancer formation (angiogenesis) and block cancer-promoting enzymes. This isoflavonoid also has antioxidant effects and stimulates natural killer lymphocytes in the immune system. Genistein can lower total cholesterol and LDL and increase "good" HDL. Genistein contributes to bone formation, with zinc promoting its effectiveness. Genistein may also lower the undesirable accompanying symptoms of menopause. Daidzein is also an isoflavonoid and phytoestrogen and has similar effects to genistein in a slightly lesser way. Other isoflavonoids are present in soy and include glycetin, daidzin, and genistin.
Soy for food supplement
Soybean extracts are available as capsules, often standardized to the content of the isoflavonoids genistein and daidzein. Furthermore, soy protein concentrates, sometimes referred to as soy protein isolates, are offered as loose powders. They usually contain 90% soy proteins and 10% other soy components, including isoflavonoids. Depending on the desired effect, soy extracts or soy proteins can be used as a dietary supplement. The dosage should also be determined accordingly.
Soybeans can be difficult to digest and cause flatulence. Indigestibility can be avoided by soaking the beans overnight and cooking them sufficiently. Soaking and cooking water should be poured away and not used in food preparation. No adverse effects are known from soybean extracts and soy proteins. Little research has been done on the use of isoflavonoids in high doses over a long period of time. Cancer patients should not consume soy products for at least one week prior to radiation therapy. The genistein it contains may protect cancer cells from the cytotoxic effects of the therapy.
- Arndt K. (HG.) (2001) Handbuch Nahrungsergänzungen-Bedeutung und Anwendung leistungssteigernder Substanzen für Bodybuilding und Kraftsport. Pages: 216-218
- Young VR, Wayler A, Garza C, Stenke FH, Murray E, Rand WM, Scrimshaw NS (1984) A long-term metabolic balance study in young men to assess the nutritional quality of an isolated soy protein and beef protein. Am J Clin Nutr 39: 8-15
- Barth CA, Scholz-Ahtens KE, Pfeuffer M, Hotze A (1990) Response of hormones and lipid metabolism to different dietary proteins. Monogr Atheroscler 16: 110-25.