Ciao, Visitatore!
 
 

🔍
RECENSIONE

Recensione

Al222
Al222 (25670 pt) 24-Oct-2024 09:24

I grassi polinsaturi sono una categoria di acidi grassi caratterizzati dalla presenza di più doppi legami nella loro struttura chimica. Questi grassi sono essenziali per il corpo umano e svolgono ruoli vitali nel mantenimento della salute cellulare e nella regolazione delle funzioni corporee. Si trovano in abbondanza negli oli vegetali, nei pesci grassi, nelle noci e nei semi. Gli acidi grassi omega-3 e omega-6 sono i due principali tipi di grassi polinsaturi e sono noti per le loro proprietà antinfiammatorie, cardioprotettive e rigeneranti, rendendoli preziosi sia nell'alimentazione che nelle applicazioni cosmetiche.

Composizione chimica e struttura

Contengono più di un doppio legame tra gli atomi di carbonio nella catena degli acidi grassi, il che li rende chimicamente reattivi e più suscettibili all'ossidazione rispetto ai grassi saturi. Gli omega-3 (come l'acido alfa-linolenico, ALA) e gli omega-6 (come l'acido linoleico, LA) sono esempi comuni. Questi acidi grassi essenziali non possono essere sintetizzati dal corpo umano e devono essere assunti attraverso l'alimentazione.

Proprietà fisiche

Si presentano tipicamente come liquidi a temperatura ambiente e sono facilmente ossidabili. Si trovano negli oli vegetali come l'olio di girasole, mais, soia, e nei pesci grassi come il salmone e lo sgombro. A causa della loro struttura chimica, hanno un punto di fusione più basso rispetto ai grassi saturi, rendendoli liquidi a basse temperature.

Processo di produzione
I grassi polinsaturi vengono estratti da fonti naturali come semi, noci e pesce. Gli oli vegetali vengono prodotti tramite estrazione a freddo o tramite processi di pressatura meccanica. Gli oli di pesce, ricchi di omega-3, vengono invece ottenuti per estrazione da pesci grassi. Dopo l'estrazione, gli oli vengono raffinati, filtrati e stabilizzati per evitare l'ossidazione.

Applicazioni

  • Medicina: I grassi polinsaturi, in particolare gli omega-3, sono utilizzati per ridurre il rischio di malattie cardiovascolari, migliorare la funzione cerebrale e ridurre le infiammazioni. Gli omega-6, sebbene necessari, devono essere bilanciati con gli omega-3 per evitare effetti pro-infiammatori. Sono comunemente prescritti sotto forma di integratori per supportare la salute cardiaca e cerebrale.

  • Cosmetici: I grassi polinsaturi vengono utilizzati nei prodotti per la cura della pelle grazie alle loro proprietà emollienti e rigenerative. Gli acidi grassi omega-3 e omega-6 aiutano a riparare la barriera cutanea, migliorano l'idratazione e riducono l'infiammazione cutanea. Vengono inclusi in creme idratanti, oli per il corpo e trattamenti anti-invecchiamento per nutrire la pelle secca e sensibile.

  • Alimentare: I grassi polinsaturi sono fondamentali in una dieta equilibrata. Si trovano in alimenti come noci, semi, oli vegetali e pesci grassi. L'assunzione di questi grassi aiuta a mantenere bassi i livelli di colesterolo cattivo (LDL) e a promuovere il colesterolo buono (HDL), contribuendo alla salute cardiovascolare.

  • Industriale: Nell'industria alimentare, i grassi polinsaturi sono utilizzati in molti prodotti alimentari trasformati come margarine, oli da cucina e condimenti. Sono apprezzati per il loro ruolo nella salute umana, ma richiedono attenzione particolare per la loro tendenza a irrancidire rapidamente, il che richiede l'uso di antiossidanti naturali per prolungarne la stabilità.

Considerazioni ambientali e di sicurezza

I grassi polinsaturi sono generalmente sicuri e salutari se consumati in quantità appropriate.  È importante evitare il riscaldamento eccessivo di oli ricchi di grassi polinsaturi, poiché questo può causare la formazione di composti ossidativi nocivi. 

La produzione sostenibile di pesce e oli vegetali è essenziale per minimizzare l'impatto ambientale.

Bibliografia__________________________________________________________________________

Siri-Tarino PW, Chiu S, Bergeron N, Krauss RM. Saturated Fats Versus Polyunsaturated Fats Versus Carbohydrates for Cardiovascular Disease Prevention and Treatment. Annu Rev Nutr. 2015;35:517-43. doi: 10.1146/annurev-nutr-071714-034449. 

Abstract. The effects of saturated fatty acids (SFAs) on cardiovascular disease (CVD) risk are modulated by the nutrients that replace them and their food matrices. Replacement of SFAs with polyunsaturated fatty acids has been associated with reduced CVD risk, although there is heterogeneity in both fatty acid categories. In contrast, replacement of SFAs with carbohydrates, particularly sugar, has been associated with no improvement or even a worsening of CVD risk, at least in part through effects on atherogenic dyslipidemia, a cluster of traits including small, dense low-density lipoprotein particles. The effects of dietary SFAs on insulin sensitivity, inflammation, vascular function, and thrombosis are less clear. There is growing evidence that SFAs in the context of dairy foods, particularly fermented dairy products, have neutral or inverse associations with CVD. Overall dietary patterns emphasizing vegetables, fish, nuts, and whole versus processed grains form the basis of heart-healthy eating and should supersede a focus on macronutrient composition.

Schulze A, Busse M. Sports Diet and Oral Health in Athletes: A Comprehensive Review. Medicina (Kaunas). 2024 Feb 13;60(2):319. doi: 10.3390/medicina60020319. 

Abstract. Food and fluid supply is fundamental for optimal athletic performance but can also be a risk factor for caries, dental erosion, and periodontal diseases, which in turn can impair athletic performance. Many studies have reported a high prevalence of oral diseases in elite athletes, notably dental caries 20-84%, dental erosion 42-59%, gingivitis 58-77%, and periodontal disease 15-41%, caused by frequent consumption of sugars/carbohydrates, polyunsaturated fats, or deficient protein intake. There are three possible major reasons for poor oral health in athletes which are addressed in this review: oxidative stress, sports diet, and oral hygiene. This update particularly summarizes potential sports nutritional effects on athletes' dental health. Overall, sports diet appropriately applied to deliver benefits for performance associated with oral hygiene requirements is necessary to ensure athletes' health. The overall aim is to help athletes, dentists, and nutritionists understand the tangled connections between sports diet, oral health, and oral healthcare to develop mitigation strategies to reduce the risk of dental diseases due to nutrition.

Cave WT Jr. Dietary omega-3 polyunsaturated fats and breast cancer. Nutrition. 1996 Jan;12(1 Suppl):S39-42. doi: 10.1016/0899-9007(96)90017-9. 

Abstract. Although early experimental investigations concluded that quantitative increases in dietary fat promote mammary tumor growth, recent studies have indicated that not all fatty acid families equally express this tumor-promoting capability. This article provides an overview of some of the experimental evidence demonstrating that the omega-6 polyunsaturated fats have significantly different mammary tumor-promoting capabilities from those of the omega-3 polyunsaturated fats. Collectively, these data indicate that whereas increasing dietary levels of omega-6 polyunsaturated fatty acids enhances tumor development, equivalent increases in dietary levels of omega-3 polyunsaturated fatty acids delay or reduce tumor development. Some of the theoretical mechanisms proposed for these contrasting results and their supporting experimental data are discussed.

Grundy SM. Effects of polyunsaturated fats on lipid metabolism in patients with hypertriglyceridemia. J Clin Invest. 1975 Feb;55(2):269-82. doi: 10.1172/JCI107930. 

Abstract. Studies were carried out on the effects of polyunsaturated fats on lipid metabolism in 11 patients with hypertriglyceridemia. During cholesterol balance studies performed in eight patients, the feeding of polyunsaturated fats, as compared with saturated fats, caused an increased excretion of endogenous neutral steroids, acidic steroids, or both in most patients. Increases in steroid excretions were marked in some patients and generally exceeded the decrement of cholesterol in the plasma compartment. The finding of a greater excretion of fecal steroids on polyunsaturated fats in hypertriglyceridemic patients contrasts to the lack of change in sterol balance previously reported for patients with familial hypercholesterolemia; however, other workers have found that polyunsaturated fats also enhance steroid excretion in normal subjects. In most of the patients, simultaneous studies were carried out on biliary lipid composition, hourly outputs of biliary lipids, and pool sizes of bile acids. In several but not all patients, fasting gallbladder bile became more lithogenic after institution of polyunsaturated fats. This increased lithogenicity was not due to a decrease in bile acid pools; in no case was the pool decreased by polyunsaturated fats. On the other hand, two patients showed an increased output of biliary cholesterol, and frequently there was an increase in fecal neutral steroids that were derived from cholesterol; thus, polyunsaturated fats may increase bile lithogenicity in some patients through mobilization of cholesterol into bile. Reductions in plasma cholesterol during the feeding of polyunsaturated fats was seen in most patients, and these changes were usually associated with a decrease in concentration of plasma triglycerides. In fact, the degree of cholesterol lowering was closely correlated with the extent of triglyceride reduction. Therefore, in hypertriglyceridimec patients polyunsaturated fats may contribute to cholesterol reduction by changing the metabolism of triglycerides or very low density lipoproteins. The findings of changes in the metabolism of cholesterol, bile acids, and triglycerides in the patients of this study suggests that polyunsaturated fats may cause a lowering of cholesterol through multiple mechanisms, and it seems unlikely that a single action can explain all the effects of these fats on the plasma lipids.

Weintraub MS, Zechner R, Brown A, Eisenberg S, Breslow JL. Dietary polyunsaturated fats of the W-6 and W-3 series reduce postprandial lipoprotein levels. Chronic and acute effects of fat saturation on postprandial lipoprotein metabolism. J Clin Invest. 1988 Dec;82(6):1884-93. doi: 10.1172/JCI113806.

Abstract. The chronic and acute effects of different types of dietary fat on postprandial lipoprotein metabolism were studied in eight normolipidemic subjects. Each person was placed for 25 d on each of three isocaloric diets: a saturated fat (SFA), a w-6 polyunsaturated fat (w-6 PUFA) and a w-3 polyunsaturated fat (w-3 PUFA) diet. Two vitamin A-fat loading tests were done on each diet. The concentrations in total plasma and chylomicron (Sf greater than 1,000) and nonchylomicron (Sf less than 1,000) fractions of retinyl palmitate (RP) were measured for 12 h postprandially. Compared with the SFA diet, the w-6 PUFA diet reduced chylomicron and nonchylomicron RP levels 56 and 38%, respectively, and the w-3 PUFA diet reduced these levels 67 and 53%, respectively. On further analysis, the main determinant of postprandial lipoprotein levels was the type of fat that was chronically fed, which appeared to mediate its effect by changing the concentration of the endogenous competitor for the system that catabolizes triglyeride-rich lipoproteins. However, there was a significant effect of the acute dietary fat load, which appeared to be due to a differential susceptibility to lipolysis of chylomicrons produced by SFA as opposed to PUFA fat loads. The levels of postprandial lipoproteins are determined by the interaction of these chronic and acute effects.

Hopkins GJ, Kennedy TG, Carroll KK. Polyunsaturated fatty acids as promoters of mammary carcinogenesis induced in Sprague-Dawley rats by 7,12-dimethylbenz[a]anthracene. J Natl Cancer Inst. 1981 Mar;66(3):517-22. 

Abstract. The development of mammary tumors was examined in female noninbred Sprague-Dawley rats fed either a low-fat diet or high-fat diets containing different fats and fatty acid esters. Each rat was given 5 mg 7,12-dimethylbenz[a]anthracene by stomach tube 1 week before diets were introduced. Addition of 3% ethyl oleate (an ethyl ester of an unsaturated fatty acid) to a diet high in saturated fat (coconut oil) had no significant effect on tumor development, but the addition of 3% ethyl linoleate (an ethyl ester of a polyunsaturated fatty acid) increased the tumor yield to about twice that in rats fed either the high-saturated fat diet or a low-fat diet. Animals fed the high-saturated fat diet containing 3% ethyl linoleate developed as many tumors as those fed a 20% sunflower seed oil diet, though the sunflower seed oil diet contained about four times as much linoleate. Rats fed a high coconut oil diet containing 3% menhaden fish oil, which contains polyunsaturated fatty acids of the linolenate family (but having little linoleic acid), also developed as many tumors as those fed the 20% sunflower seed oil diet. These differences in mammary tumor yield could not be explained by alterations in the serum levels of prolactin, estrogen, or progesterone. However, the higher tumor yields were associated with increased unsaturation of mammary tissue phospholipids.