La soia è una piantina annuale appartenenta alla famiglia delle Fabaceae.
E' uno dei vegetali più coltivati al mondo ed è utilizzata nell'alimentazione umana ed animale.
La soia naturale non è transgenica, quindi non ha subito modifiche al proprio DNA.
E' una leguminacea (al pari di fagioli, piselli ecc) introdotta come alternativa al mais per il basso costo e per evitarne le micotossine sulla granella e altri parassiti.
La diffusione della soia è dovuta alla crescente richiesta dei consumatori che hanno scoperto alcune proprietà interessanti di questo legume.
- Ottima digeribilità
- Alto contenuto proteico (la soia è composta al 40% da proteine e al 20% da grassi)
- Alto contenuto di fibre
Ma il parametro che l'ha fatta progredire sul mercato è il basso costo.
Ne esistono in commercio una trentina di varietà :
Fukui, Demetra, Blanca, Taira, Regir, Dekabig, Atlantic, Bahia, PR92B63, Pacific, Nikko, Nikir, Condor, Pedro, Giulietta, Tea, Ascasubi, Brillante, Colorado, Fortezza, Sapporo, Goriziana, Aires, Sponsor, Indian, Hilario, Neoplanta, Cresir, Shama, Syngenta, Sekoia
Dalla soia si ricavano:
- semi dai quali si produce principalmente la farina
- germogli, utilizzati per insalate ed altre applicazioni nei settori farmaceutici e cosmetici.
La soia contiene diversi composti polifenolici, in particolare gli isoflavoni, che hanno effetti positivi sulla salute umana, ma la loro presenza in percentuale varia a seconda del tipo di soia.
Studi
Gli isoflavoni (classificati come fitoestrogeni), hanno dimostrato potenzialità positive contro malattie cardiovascolari, diabete, cancro. osteoporosi e disturbi neurogenerativi. Nella soia sono stati identificati 12 differenti tipi divisi in:
agliconi (daizein, glicitein, genistein)
beta-glucosidi (daidzin, glicitin, genistin) (1)
Nel 1999 la FDA aveva riconosciuto alle proteine della soia una certa protezione contro il rischio di malattia coronarica ed aveva autorizzato la seguente posologia: 25 grammi di proteine di soia al giorno nell'ambito di una dieta povera di grassi e colesterolo.
Nel 2017 la FDA annunciava l'intenzione di rivedere l'autorizzazione per carenza di dati scientifici in quanto solamente 19 studi confermavano l'utilità della soia nel ridurre il rischio coronarico, mentre 27 studi non supportavano questa tesi positiva.
E' un alimento piuttosto discusso.
Da una parte, alcuni studi richiamano l'attenzione sugli isoflavoni presenti nella soia che aiutano a difendere il sistema cardiovascolare regolando le funzioni cellulari ed enzimatiche in situazioni come l'infiammazione, la trombosi e la progressione arteriosclerotica (2).
Da un'altra parte, si teme che possa causare danni, in particolar modo il morbo di Alzheimer, se ingerita in forma di prodotto industriale. Questo studio analizza il problema (3).
Tuttavia, una certa quantità di studi scientifici posteriori al 2017 confermano l'attività positiva della soia sulla salute umana.
In una gara ciclistica di 20 km, un estratto di soia fermentata ha migliorato le prestazioni degli atleti sia in termini di potenza che di velocità (4).
Pazienti con diabete tipo 2 hanno ottenuto miglioramento delle condizioni glicemiche, aumento del flusso sanguigno brachiale, miglioramento della funzione endoteliale, aumento gli antiossidanti totali del siero e del profilo lipidico. Non c'è stato invece alcun effetto significativo sulla pressione sanguigna e sul colesterolo HDL (5)
La soia ed i suoi isoflavoni esercitano una positiva influenza sui rischi di mortalità associati a cancro e a disturbi cardiovascolari (6).
Farina di soia studi
Bibliografia_______________________________________________________________
(1) Orts A, Revilla E, Rodriguez-Morgado B, Castaño A, Tejada M, Parrado J, García-Quintanilla A. Protease technology for obtaining a soy pulp extract enriched in bioactive compounds: isoflavones and peptides Heliyon. 2019 Jun 22;5(6):e01958. doi: 10.1016/j.heliyon.2019.e01958.
Abstract. This work presents a new bioprocess process for the extraction of bioactive components from soy pulp by-product (okara) using an enzymatic technology that was compared to a conventional water extraction. Okara is rich in fiber, fat, protein, and bioactive compounds such as isoflavones but its low solubility hampers the use in food and fertilizer industry. After the enzymatic attack with endoproteases half of the original insoluble proteins were converted into soluble peptides. Linked to this process occured the solubilization of isoflavones trapped in the insoluble protein matrix. We were able to extract up to 62.5% of the total isoflavones content, specially aglycones, the more bioactive isoflavone forms, whose values rose 9.12 times. This was probably due to the increased solubilization and interconversion from the original isoflavones. In conclusion, our process resulted in the formulation of a new functional product rich in aglycones and bioactive peptides with higher antioxidant potency than the original source. Therefore, we propose that the enzymatic extraction of okara bioactive compounds is an advantageous tool to replace conventional extraction.
(2) González Cañete N, Durán Agüero S. Soya isoflavones and evidences on cardiovascular protection. Nutr Hosp. 2014 Jun 1;29(6):1271-82. doi: 10.3305/nh.2014.29.6.7047. Spanish.
(3) Roccisano D, Henneberg M, Saniotis A. A possible cause of Alzheimer's dementia - industrial soy foods. Med Hypotheses. 2014 Mar;82(3):250-4. doi: 10.1016/j.mehy.2013.11.033. Epub 2013 Dec 7.
(4) Seeley AD, Jacobs KA, Signorile JF. Acute Soy Supplementation Improves 20-km Time Trial Performance, Power, and Speed. Med Sci Sports Exerc. 2020 Jan;52(1):170-177. doi: 10.1249/MSS.0000000000002102.
Abstract. Introduction: Isoflavones, a chemical class of phytoestrogens found in soybeans and soy products, may have biological functions similar to estradiol. After binding with ERβ or perhaps independently of estrogen receptors, isoflavones may augment vascular endothelial relaxation, contributing to improved limb blood flow. Purpose: To determine if acute fermented soy extract supplementation influences 20-km time trial cycling performance and cardiac hemodynamics compared with a placebo. Methods: Subjects included 25 cyclists and triathletes (31 ± 8 yr, V˙O2peak: 55.1 ± 8.4 mL·kg·min). Each subject completed a V˙O2peak assessment, familiarization, and two 20-km time trials in randomized order after ingestion of a fermented soy extract supplement or placebo. The fermented soy extract consisted of 30 g powdered supplement in 16 fl. ounces of water. The placebo contained the same quantities of organic cocoa powder and water. Each trial consisted of 60 min of rest, 30 min at 55% Wpeak, and a self-paced 20-km time trial. Results: Soy supplementation elicited a faster time to 20-km completion (-0.22 ± 0.51 min; -13 s), lower average HR (-5 ± 7 bpm), and significantly greater power (7 ± 3 W) and speed (0.42 ± 0.16 km·h) during the last 5 km of the time trial compared with placebo. Analysis of the results by relative fitness level (<57 vs ≥ 57 mL⋅kg⋅min) indicated that those with a higher level of fitness reaped the largest performance improvement alongside a reduced HR (-5 ± 7 bpm). Conclusions: Ingestion of a fermented soy extract supplement improved sprint-distance performance through improvements in both power and speed. For those with great aerobic fitness, soy supplementation may help to decrease cardiac demand alongside performance improvement.
(5) Sedaghat A, Shahbazian H, Rezazadeh A, Haidari F, Jahanshahi A, Mahmoud Latifi S, Shirbeigi E. The effect of soy nut on serum total antioxidant, endothelial function and cardiovascular risk factors in patients with type 2 diabetes. Diabetes Metab Syndr. 2019 Mar - Apr;13(2):1387-1391. doi: 10.1016/j.dsx.2019.01.057
(6) Nachvak SM, Moradi S, Anjom-Shoae J, Rahmani J, Nasiri M, Maleki V, Sadeghi O. Soy, Soy Isoflavones, and Protein Intake in Relation to Mortality from All Causes, Cancers, and Cardiovascular Diseases: A Systematic Review and Dose-Response Meta-Analysis of Prospective Cohort Studies J Acad Nutr Diet. 2019 Jul 2. pii: S2212-2672(19)30362-4. doi: 10.1016/j.jand.2019.04.011
Woo HW, Kim MK, Lee YH, Shin DH, Shin MH, Choi BY. Habitual consumption of soy protein and isoflavones and risk of metabolic syndrome in adults ≥ 40 years old: a prospective analysis of the Korean Multi-Rural Communities Cohort Study (MRCohort). Eur J Nutr. 2019 Oct;58(7):2835-2850. doi: 10.1007/s00394-018-1833-8.
Abstract. Purpose: Although considerable attention has been paid to the potential benefits of soy protein and isoflavones for preventing metabolic syndrome (MetS) and its components, findings linking habitual consumption of these factors to MetS are limited. This study aimed to evaluate the association of MetS incidence with habitual intake of soy protein/isoflavones among Korean men and women aged ≥ 40 years old who did not have MetS at baseline (n = 5509; 2204 men and 3305 women). Methods: Dietary intake of soy protein/isoflavones at baseline and average consumption during follow-up were used. Results: A significant inverse association between dietary intake and incidence of MetS was found in women (incidence rate ratios, IRR = 0.60, 95% CI = 0.46-0.78, P for trend = 0.0094 for the highest quintile of average soy protein intake compared with the lowest quintile; IRR = 0.57, 95% CI = 0.44-0.74, P for trend = 0.0048 for the highest quintile of average isoflavones intake compared with the lowest quintile). A tendency towards an inverse association was also found in men, although it was not significant for the highest quintile (IRR = 0.80, 95% CI = 0.58-1.11, P for trend = 0.9759, comparing the lowest to the highest quintile of average soy protein intake; IRR = 0.73, 95% CI = 0.53-1.01, P for trend = 0.8956, comparing the lowest to the highest quintile of average isoflavones intake). In terms of individual abnormalities, a significant inverse association was found between soy protein and isoflavones and the incidence of low-high-density lipoprotein cholesterol in both men and women. Abdominal obesity and elevated blood pressure were inversely related to soy protein/isoflavones only in women, and an inverse association of elevated triglyceride appeared only in men. Conclusion: Our findings suggest that habitual intake of soy protein and isoflavones is inversely associated with the risk of MetS and its components. There is likely to be a reverse J-shaped association of average intake with MetS.
