I grassi saturi sono una classe di acidi grassi caratterizzati dall'assenza di doppi legami tra gli atomi di carbonio nella loro struttura chimica. Sono solidi a temperatura ambiente e si trovano principalmente in alimenti di origine animale come carne, burro, latticini e alcuni oli vegetali, come l'olio di cocco e l'olio di palma. I grassi saturi sono spesso associati al rischio di malattie cardiovascolari, ma in quantità moderate possono fornire energia e sostenere alcune funzioni corporee. Sono anche ampiamente utilizzati in applicazioni cosmetiche grazie alle loro proprietà emollienti e stabilizzanti.

Composizione chimica e struttura

Questo tipo di grassi non presenta doppi legami nella loro struttura chimica, il che significa che tutti gli atomi di carbonio sono legati al massimo numero possibile di atomi di idrogeno. Questa struttura conferisce ai grassi saturi maggiore stabilità chimica e li rende meno suscettibili all'ossidazione rispetto ai grassi polinsaturi. Tra gli esempi comuni di acidi grassi saturi troviamo l'acido palmitico, l'acido stearico e l'acido laurico.

Proprietà fisiche

Risultano solidi a temperatura ambiente e hanno punti di fusione più elevati rispetto ai grassi insaturi. Questo li rende adatti per l'uso in prodotti da forno e per la frittura, in quanto rimangono stabili a temperature elevate. Sono presenti in alimenti come burro, strutto, formaggi e oli tropicali come l'olio di cocco e l'olio di palma.

Processo di produzione

I grassi saturi vengono estratti principalmente da fonti animali e vegetali. I grassi animali, come il burro e il lardo, sono ottenuti tramite la lavorazione del latte o il riscaldamento del grasso animale. Gli oli vegetali saturi, come l'olio di cocco e di palma, vengono estratti tramite pressatura a freddo o metodi di estrazione a base di solventi dalle noci di cocco o dai frutti di palma. Questi oli vengono poi raffinati e stabilizzati per garantire una lunga durata.

Applicazioni

• Medicina: I grassi saturi sono stati associati a un aumento del colesterolo LDL, che può aumentare il rischio di malattie cardiovascolari. Tuttavia, recenti studi suggeriscono che il loro ruolo è più complesso e che una moderata assunzione di grassi saturi può non essere così dannosa se bilanciata con una dieta ricca di grassi insaturi. Alcuni grassi saturi come l'acido laurico, presente nell'olio di cocco, sono stati studiati per le loro proprietà antimicrobiche.

• Cosmetici: I grassi saturi sono comunemente utilizzati nei prodotti cosmetici per le loro proprietà emollienti e stabilizzanti. Gli acidi grassi saturi, come l'acido stearico, vengono utilizzati in creme e lozioni per migliorare la texture e aumentare la stabilità del prodotto. I grassi saturi forniscono idratazione alla pelle, formando una barriera protettiva che aiuta a prevenire la perdita d'acqua.

• Alimentare: I grassi saturi sono ampiamente utilizzati nell'industria alimentare per la preparazione di prodotti da forno, dolci, snack e per la frittura, grazie alla loro stabilità a temperature elevate. Il burro, lo strutto e gli oli tropicali sono comuni in molte preparazioni culinarie.

• Industriale: Nell'industria alimentare e cosmetica, i grassi saturi sono usati come stabilizzanti e addensanti. Sono apprezzati per la loro capacità di mantenere la consistenza dei prodotti a lungo termine, e la loro stabilità chimica li rende ideali per prodotti che devono avere una lunga durata di conservazione.

Considerazioni ambientali e di sicurezza

L'eccessivo consumo di grassi saturi è stato collegato a un aumento del rischio di malattie cardiovascolari, sebbene il loro ruolo specifico nella dieta sia ancora oggetto di dibattito. È importante consumare i grassi saturi con moderazione e bilanciare la dieta con grassi insaturi. Dal punto di vista ambientale, la produzione di oli saturi come l'olio di palma è spesso associata a problemi di deforestazione e perdita di biodiversità, rendendo essenziali pratiche di produzione sostenibile.

Bibliografia__________________________________________________________________________

Bier DM. Saturated Fats and Cardiovascular Disease: Interpretations Not as Simple as They Once Were. Crit Rev Food Sci Nutr. 2016 Sep 9;56(12):1943-6. doi: 10.1080/10408398.2014.998332. 

Abstract. Historically, the so-called "lipid hypothesis" has focused on the detrimental role of saturated fats per se in enhancing the risks of cardiovascular disease. Recently, a body of new information and systematic analyses of available data have questioned simple interpretation of the relationship of dietary saturated fats and of individual saturated fatty acids to CVD risk. Thus, current assessments of risks due to dietary fat consumption that emphasize the confounding nature of the dietary macronutrients substituted for dietary saturated fats and give broader recognition to the effect of patterns of food intake as a whole are the most productive approach to an overall healthy diet.

Risérus U, Willett WC, Hu FB. Dietary fats and prevention of type 2 diabetes. Prog Lipid Res. 2009 Jan;48(1):44-51. doi: 10.1016/j.plipres.2008.10.002.

Abstract. Purpose of review: The adverse cardiovascular health effects of saturated fats have been debated recently since the publication of studies reporting no increase in cardiovascular risk with saturated fat intakes. We purport that this may be because of the varied nature of saturated fats, which range in length from 2 to over 20 carbon atoms, and review evidence surrounding the cardiovascular health effects of medium-chain triglycerides (MCT). Recent findings: MCTs are saturated fats of shorter chain length than other, more readily consumed saturated fats. Studies have reported that consumption of MCT may lead to improvements in body composition without adversely affecting cardio-metabolic risk factors. There may also be synergistic actions between MCT and n-3 polyunsaturated fats that may lead to improvements in cardiovascular health. Summary: It is clinically relevant to distinguish between sources of saturated fats for cardiovascular health. Medium, and possibly shorter chain, saturated fats behave differently than long-chain saturated fats and should not be judged similarly when it comes to their cardio-metabolic health effects. Given their neutral, and potentially beneficial cardiovascular health effects, they should not be categorized together.

Hu FB, Stampfer MJ, Manson JE, Ascherio A, Colditz GA, Speizer FE, Hennekens CH, Willett WC. Dietary saturated fats and their food sources in relation to the risk of coronary heart disease in women. Am J Clin Nutr. 1999 Dec;70(6):1001-8. doi: 10.1093/ajcn/70.6.1001. 

Abstract. Background: Metabolic studies suggest that saturated fatty acids differ in their effects on blood lipids. Objective: The objective was to examine the associations between intakes of individual saturated fatty acids and their food sources in relation to the risk of coronary heart disease (CHD). Design: This was a prospective cohort study of 80082 women in the Nurses' Health Study aged 34-59 y. Subjects had no known cardiovascular disease, cancer, hypercholesterolemia, or diabetes, and completed validated food-frequency questionnaires in 1980. Results: During 14 y of follow-up, we documented 939 incident cases of major CHD events. In multivariate analyses in which age, smoking, and other covariates were controlled for, intakes of short- to medium-chain saturated fatty acids (4:0-10:0) were not significantly associated with the risk of CHD. In contrast, intakes of longer-chain saturated fatty acids (12:0-18:0) were each separately associated with a small increase in risk. The multivariate RR for a 1% energy increase from stearic acid was 1.19 (95% CI: 1.02, 1.37). The ratio of polyunsaturated to saturated fat was strongly and inversely associated with CHD risk (multivariate RR for a comparison of the highest with the lowest deciles: 0.58; 95% CI: 0.41, 0.83; P for trend < 0.0001). Conversely, higher ratios of red meat to poultry and fish consumption and of high-fat to low-fat dairy consumption were associated with significantly greater risk. Conclusion: A distinction between stearic acid and other saturated fats does not appear to be important in dietary advice to reduce CHD risk, in part because of the high correlation between stearic acid and other saturated fatty acids in typical diets.

Hayes KC. Saturated fats and blood lipids: new slant on an old story. Can J Cardiol. 1995 Oct;11 Suppl G:39G-46G. 

Abstract. In recent years the association between dietary saturated fat, hypercholesterolemia, and coronary artery disease has been re-explored. Prompted largely by the notion that dietary fats, and their attendant fatty acids, can specifically influence the distribution of the plasma cholesterol between low density (LDL) and high density (HDL) lipoprotein cholesterol, the focus of the original research has shifted from total cholesterol to lipoproteins. Several new, sometimes controversial, concepts have arisen that challenge underlying assumptions of the Keys-Hegsted regression equations. First, although saturated fats as a class raise LDL, they also appear to have primary responsibility among dietary fatty acids for raising HDL, possibly depending on a balanced intake of polyunsaturated fats. Second, not all saturated fatty acids are equally responsible for changes in LDL or HDL. Only natural triglycerides (TG) rich in lauric (12:0) and myristic (14:0) acids are especially cholesterolemic, whereas 16:0-rich fats can be neutral or cholesterol-raising depending on the metabolic circumstances (lipoprotein setpoint) of the host. In normolipemic individuals with normal lipoprotein metabolism, dietary palmitic acid (16:0) typically appears neutral. When lipoprotein metabolism is impaired, eg, if LDL receptor activity is depressed by the presence of dietary cholesterol, consumption of 16:0-rich TGs can contribute to hypercholesterolemia. Although stearic acid (18:0) is typically considered neutral, exaggerated consumption of 18:0-rich fat (cocoa butter) lowers both LDL and HDL. ....

Bhavsar N, St-Onge MP. The diverse nature of saturated fats and the case of medium-chain triglycerides: how one recommendation may not fit all. Curr Opin Clin Nutr Metab Care. 2016 Mar;19(2):81-7. doi: 10.1097/MCO.0000000000000249.

Abstract. Purpose of review: The adverse cardiovascular health effects of saturated fats have been debated recently since the publication of studies reporting no increase in cardiovascular risk with saturated fat intakes. We purport that this may be because of the varied nature of saturated fats, which range in length from 2 to over 20 carbon atoms, and review evidence surrounding the cardiovascular health effects of medium-chain triglycerides (MCT). Recent findings: MCTs are saturated fats of shorter chain length than other, more readily consumed saturated fats. Studies have reported that consumption of MCT may lead to improvements in body composition without adversely affecting cardio-metabolic risk factors. There may also be synergistic actions between MCT and n-3 polyunsaturated fats that may lead to improvements in cardiovascular health. Summary: It is clinically relevant to distinguish between sources of saturated fats for cardiovascular health. Medium, and possibly shorter chain, saturated fats behave differently than long-chain saturated fats and should not be judged similarly when it comes to their cardio-metabolic health effects. Given their neutral, and potentially beneficial cardiovascular health effects, they should not be categorized together.