These are very high percentages, much higher than those of meat and fish, which contain about 20-25 grams of protein for each pound of product.
, and this negatively affects the use of other amino acids in protein synthesis.Equally well known is the concept of mutual integration, which is based on the complementarity of plant proteins; in practice, the amino acid deficiencies of two complementary protein sources are compensated for each other. In particular, as regards soy proteins, the complementary source is represented by cereal proteins; It is no coincidence that Asian populations have empirically intuited for centuries the importance of associating soy with cereals, such as miso soups or shoyu (wheat and soy sauce).
Protein quality of soy protein isolate
At this point it should be pointed out that the quality of isolated soy proteins is superior to that of proteins obtained from the ingestion of whole seeds or soy-based foods.
Thanks to the high content of glutamine, arginine and branched chain amino acids, as well as to the methods of extraction and processing, the isolated soy proteins recorded the highest protein quality score in the new index developed by the World Health Organization (WHO).
We are talking about the PDCAAS, which to establish the quality of a protein source takes into account both the amino acid content and its digestibility. The maximum PDCAAS score is 1.0, so all proteins with a score of 1.0 are considered complete for humans. As anticipated, soy protein isolate, along with casein, whey and whey proteins. "egg, they scored a perfect 1.0; beef, on the other hand, scored only 0.92, followed by soybeans with a score of 0.91.
Below we report the amino acid composition of different protein supplements, in order to obtain an immediate comparison between soy proteins and those of whey and egg; note that the sum of the individual amino acids does not coincide perfectly with the total protein content (due to technical defects that can be found in practically all manufacturers' cards).
- Isolated
- concentrated by microfiltration
- Isolate by ultramicrofiltration
All these foods contain, in addition to the protein fraction, many other substances that give the soy all those properties that we are going to analyze; many of these characteristics, when specified, are to be attributed to isoflavones, the indicative content of which in the various products is reported in this article.
Effects on Cholesterol and Cardiovascular Diseases
An advantage of soy proteins over animal proteins is the low content of cholesterol and saturated fats, a characteristic that gives the legume preventive properties in cardiovascular diseases. This property led the "FDA, the US sovereign body that regulates the safety of drugs and food, to allow the following message to be published on the label in 1998:" 25 grams of soy protein per day, in the context of a diet low in saturated fat and cholesterol, can help lower the risk of heart disease ".
However, this property of soy and its proteins remains somewhat controversial, given the presence of studies that have not shown any benefit in this regard; It should also be noted that - given the indication to consume proteins together with a diet low in fat and cholesterol - the expected results could be linked to the low-fat diet rather than to soy proteins.
Menopause and Breast Cancer
The same uncertainties grip the researchers' judgment on the other alleged positive effects deriving from the regular consumption of soy; the presence of the now famous isoflavones, for example, has been linked to a lower incidence of breast, prostate and endometrial cancer, hot flashes in menopause and osteoporosis; these plant substances, given the ability to bind to the estrogen receptors, stimulating them in a rather mild way, would balance the endocrine balance of the woman, preventing the excessive activity of estrogens during the fertile age and compensating for its deficiency in the post-menopausal period. Even in this case, however, only a part of the studies supports these hypotheses, which are therefore still awaiting confirmation.
Soy: goitrogen food?
On the opposite front, just to give an idea of how delicate the question is, there are scholars who strongly advise against the intake of phytoestrogens, especially during puberty; these substances could in fact stimulate undesirable growth processes in girls and interfere with the normal endocrine development of boys. Some researchers even hypothesize a relationship between the high intake of plant estrogens and the increase in male infertility; others relate the high consumption of soy with an increased risk of hypothyroidism and thyroid goiter. As mentioned, we are always talking about soy food derivatives, and not isolated soy proteins, sold as a high protein supplement (90%); in this sense, in fact, it has been seen that the constant intake of a soy protein isolate can increase the production of thyroxine (T4), thyrotropic hormone (TSH), triiodothyronine (T3) and also insulin.
, fish and whole grains, vegetables, fruit and legumes, even other than soy. In addition, overeating is less frequent, so much so that a popular saying reminds us that the real secret to longevity is to get up from the table before being completely full., which block the digestion of proteins, and significant quantities of phytates, which by binding to some minerals, such as calcium, magnesium, manganese, zinc, copper and iron, reduce their absorption. Once again the Asian populations teach, given that the long traditional fermentation of soy, necessary to produce the various sauces and miso pastes, destroys significant quantities of these antinutrients; modern industrial processes, used to produce soy sauces, soy milk, tofu and imitations of meat, on the other hand, do not they eliminate these harmful elements.
Food Allergies, Pregnancy and Disputes
Soy proteins are often responsible for food allergies, so much so that their allergenic potential is second only to peanuts.
The vast majority of soy on the market is of genetically modified origin; moreover, behind this legume there are the flower of multinationals (including Monsanto), which have every interest in promoting its use in human nutrition (the consumer is willing to pay gold for what (he believes ) can keep it healthy).
All these shadows clash sharply with the image of soy painted by the producers, who describe it as a panacea and an ideal substitute for animal proteins. The truth is that at the moment it is simply impossible to draw firm conclusions on the relationship between soy consumption and prevention. of any disease or disorder; the selection of published studies can in fact be easily operated to obtain a "distorted image, both in a positive and negative sense."
Fortunately, logic and common sense come to the rescue, suggesting that problems related to the intake of soy proteins within the limits of a balanced diet should be excluded; on the other hand, the widespread tendency to take large quantities of soy supplements or products that contain it, in the illogical belief that this helps in the prevention of certain diseases. Unfortunately, we still do not know for sure whether ingesting soy in large quantities in the form of food or supplements is beneficial or harmful; considering that studies in merit have been going on for many years and given the large amount of factors that come into play in the genesis of disorders and diseases related to soy consumption (both in a positive and negative sense), it is likely that we will never have a definitive answer.
Note: pregnant women (even when it is only sought) and breastfeeding should avoid the high consumption of soy protein of food origin or specific supplements. The same goes for women with estrogen receptor positive cancer, unless otherwise prescribed. medical.
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