Polyunsaturated fats are a category of fatty acids characterized by the presence of multiple double bonds in their chemical structure. These fats are essential for the human body and play crucial roles in maintaining cellular health and regulating bodily functions. They are abundant in plant-based oils, fatty fish, nuts, and seeds. Omega-3 and omega-6 fatty acids are the two main types of polyunsaturated fats and are known for their anti-inflammatory, heart-protective, and regenerative properties, making them valuable in both dietary and cosmetic applications.

Chemical Composition and Structure

Polyunsaturated fats contain more than one double bond between carbon atoms in the fatty acid chain, making them chemically reactive and more prone to oxidation compared to saturated fats. Omega-3s (such as alpha-linolenic acid, ALA) and omega-6s (such as linoleic acid, LA) are common examples. These essential fatty acids cannot be synthesized by the human body and must be obtained through diet.

Physical Properties

Polyunsaturated fats are typically liquid at room temperature and are easily oxidized. They are found in plant oils such as sunflower, corn, soybean, and in fatty fish like salmon and mackerel. Due to their chemical structure, they have a lower melting point than saturated fats, making them liquid at lower temperatures.

Production Process

Polyunsaturated fats are extracted from natural sources such as seeds, nuts, and fish. Vegetable oils are produced through cold extraction or mechanical pressing processes. Fish oils, rich in omega-3s, are extracted from fatty fish. After extraction, oils are refined, filtered, and stabilized to prevent oxidation.

Applications

• Medical: Polyunsaturated fats, especially omega-3s, are used to reduce the risk of cardiovascular diseases, improve brain function, and reduce inflammation. Omega-6s, while necessary, must be balanced with omega-3s to avoid pro-inflammatory effects. They are commonly prescribed as supplements to support heart and brain health.

• Cosmetics: Polyunsaturated fats are used in skincare products for their emollient and regenerative properties. Omega-3 and omega-6 fatty acids help repair the skin barrier, improve hydration, and reduce skin inflammation. They are included in moisturizers, body oils, and anti-aging treatments to nourish dry and sensitive skin.

• Food: Polyunsaturated fats are a key component of a balanced diet. They are found in foods like nuts, seeds, vegetable oils, and fatty fish. Consuming these fats helps maintain low levels of bad cholesterol (LDL) and promotes good cholesterol (HDL), contributing to cardiovascular health.

• Industry: In the food industry, polyunsaturated fats are used in various processed foods such as margarine, cooking oils, and dressings. They are valued for their role in human health but require special attention due to their tendency to spoil quickly, requiring the use of natural antioxidants to extend their shelf life.

Environmental and Safety Considerations

Polyunsaturated fats are generally safe and healthy when consumed in appropriate amounts. However, excessive use, particularly when the balance between omega-3 and omega-6 is skewed, can have negative effects. It is important to avoid overheating oils rich in polyunsaturated fats, as this can result in the formation of harmful oxidative compounds. Sustainable production of fish and plant oils is essential to minimize environmental impact.

References__________________________________________________________________________

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.