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Soy protein

Soy protein is a purely vegetable protein made from soybeans. Even though vegetable proteins generally have the reputation of having a lower biological value compared to animal proteins, this is not the case with soy protein. Soy protein is a so-called complete protein that contains all the amino acids essential for humans. Soy protein has the highest biological value of all plant proteins with a value of 84 and is therefore 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 are said to 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 this could occur in humans.

Soybeans have a high content of oils and proteins. The latter contain many high-quality essential amino acids, including glutamine, arginine, lysine, leucine and isoleucine. Soy proteins are comparable in quality to animal proteins and are therefore used in the production of "artificial meat". Soybean oils are used for the production of margarines. Other components of soybeans are used in the production of flour, milk, yogurt and quark. Young soybean seedlings can also be eaten as sprouted vegetables. In addition to fats (including 55% essential linoleic acid), proteins and carbohydrates, soybeans contain a range 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 values of all plant proteins
  • Is a purely plant-based alternative to whey protein before and after training due to its fast digestion speed
  • Lactose-free and also suitable for people who suffer 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 casein and significantly higher than that of whey.
  • Unlike other proteins, soy protein can help to raise thyroid hormone levels, which is helpful for bodybuilders on a diet. It also often improves blood lipid levels.
  • One of the isoflavones in soy, known as daidzein, has been shown to increase testosterone and growth hormone levels in male test animals. There was also less muscle mass loss during a diet compared to casein.

Soybeans (Glycine max) belong to the legume family and are originally native to East Asia, Africa and Australia. The Chinese cultivated the soybean plant around 3000 years ago, but it was not until the 19th century that it was 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, while their seeds, the soybeans, can be used in a variety of ways for human consumption. In Asia, soy has long been regarded not only as a nutritious plant, but the health benefits 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.

Like whey protein, soy protein is a fast-digesting protein source that causes a significant increase in amino acid levels in the blood just 30 to 45 minutes after consumption and quickly supplies your body and muscles with important protein building blocks. Furthermore, soy protein is easy to digest and well tolerated, so that it does not place a particularly heavy burden on the digestive system and can therefore also be consumed shortly before training.

Soy protein contains so-called phytosterols, which can lower cholesterol levels, which can have positive effects on cardiovascular health. Furthermore, soy protein contains isoflavones, which act as anti-oestrogens 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 suitable as a source of protein for vegetarians and vegans, as it has one of the highest biological values of all plant proteins. However, soy protein is also very popular with many non-vegetarians, which is not only due to the health benefits mentioned above. As soy protein naturally contains no 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 rapid digestibility mentioned above suggests, soy protein is very suitable for use before, during and immediately after training. Even in the morning, when your body's amino acid levels have reached a low point after an overnight fast, a fast-digesting protein such as 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 the day to meet your protein needs.

People from Asian countries consume around 15 to 40 mg of soy per day in their traditional diet. In our country, soy products are rarely used, so we usually consume less than 2 mg per day. Soy can help protect against cardiovascular diseases and cancer. It helps to lower total cholesterol, LDL cholesterol and triglycerides. Replacing animal proteins with soy proteins can have a cholesterol-lowering effect, especially if cholesterol levels are high. Soy can presumably also help to lower blood pressure and reduce the peroxidation of lipoproteins. In the USA, it is therefore now permitted for foods containing soy protein to carry the claim that consumption contributes to the prevention of 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 cancer) occur far less frequently. This may be due to the high consumption of soy products. Soy can also increase bone density and thus help protect against osteoporosis. In menopausal women, some of the typical symptoms may be alleviated. Soy proteins can lower hematocrit (the proportion of red blood cells) and reduce blood thickness. They can make it easier to lose weight during weight-reduction diets and promote muscle growth.

Isoflavonoids - the most important phytamines in soy

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 of which has a similar effect on different types of cancer. They all have a similar structure to oestrogens, but with a much weaker effect. Isoflavonoids are therefore often referred to as phytoestrogens. Isoflavonoids are distributed differently in the soybean, with the highest amounts in the seed hulls. 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 researched so far. It can have estrogenic effects, but can 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 the natural killer lymphocytes in the immune system. Genistein can lower total cholesterol and LDL and increase the "good" HDL. Genistein contributes to bone formation, with zinc promoting its effectiveness. Genistein can also reduce the unwanted symptoms associated with the menopause. Daidzein is also an isoflavonoid and phytoestrogen and has somewhat similar effects to genistein. Soy contains other isoflavonoids, including glycetin, daidzin and genistin.

Soy as a dietary supplement

Soybean extracts are available as capsules, which are often standardized to contain the isoflavonoids genistein and daidzein. Soy protein concentrates, sometimes referred to as soy protein isolates, are also available as loose powders. They usually contain 90% soy protein 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 for food preparation. Soybean extracts and soy proteins are not known to have any negative effects. The use of isoflavonoids in high doses over a long period of time has been little researched. Cancer patients should not consume soy products for at least one week prior to radiotherapy. The genistein it contains can protect the cancer cells from the cytotoxic effects of the therapy.

References

  1. Arndt K. (HG.) (2001) Handbuch Nahrungsergänzungen-Bedeutung und Anwendung leistungssteigernder Substanzen für Bodybuilding und Kraftsport. Pages: 216-218
  2. 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
  3. 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