Deciphering the Health Code of Lipids: Understanding the Close Relationship Between Fatty Acid Classification and Cardiovascular Health

Soybeans have a protein content as high as 36%–40%, while other legumes, such as red beans and mung beans, have a protein content of about 20%. Meat (including livestock, poultry, fish, and shrimp) contains 15%–20% protein. Eggs contain 11%–14% protein. Milk contains about 3% protein. All of these sources are considered high-quality proteins and should account for one-third to one-half of total dietary protein. Grains contain about 10% protein; although this is not high, grains are a staple food and are consumed in large quantities, making them an important source of dietary protein.

lipids

Lipids in food include two parts: fats and lipids. Fats: Animal-derived fats, such as butter, mutton fat, and lard; plant-derived fats, such as peanut oil, soybean oil, corn oil, rapeseed oil, and olive oil. Fats are composed of one molecule of glycerol and three molecules of fatty acids, hence the name triglycerides. Lipids: Include phospholipids, glycolipids, and sterols (cholesterol, which is of concern to many, is a type of sterol). (I) Classification of Fatty Acids and Their Impact on Human Cardiovascular Health. Fatty acids that make up fats are classified into many categories according to their molecular structure.

1. Saturated fatty acids

Saturated fatty acids are fatty acids whose carbon chains lack double bonds. Animal fats, such as lard and tallow, as well as tropical vegetable oils, such as palm oil and coconut oil, are high in saturated fatty acids. Saturated fatty acids can raise total cholesterol and low-density lipoprotein cholesterol (bad cholesterol) in the blood, so they should not be consumed in large quantities. Foods high in saturated fatty acids also include fatty meat, chicken skin, and duck skin.

2. Monounsaturated fatty acids

Monounsaturated fatty acids are fatty acids with only one double bond on their carbon chain. They are abundant in olive oil and camellia oil. The low incidence of heart disease among residents of the Mediterranean region is related to their high consumption of monounsaturated fatty acids. Monounsaturated fatty acids can lower low-density lipoprotein cholesterol (bad cholesterol) in the blood and maintain high-density lipoprotein cholesterol (good cholesterol) at a relatively high level.

3. Polyunsaturated fatty acids and essential fatty acids

Polyunsaturated fatty acids are fatty acids containing two or more double bonds on the carbon chain of their molecules. Linoleic acid and α-linolenic acid cannot be synthesized in the human body and must be obtained from the diet; these two fatty acids are called essential fatty acids. Peanut oil, corn oil, sunflower oil, sesame oil, and soybean oil are rich in polyunsaturated fatty acids. Although polyunsaturated fatty acids have various effects, such as lowering blood lipids, they are prone to lipid peroxidation, producing free radicals that can damage cells; therefore, they should not be consumed in excess.

When choosing edible oils, the appropriate ratio of the three types of fatty acids mentioned above should be considered. The ideal ratio of saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids in dietary fats is 1:1.5:1. Polyunsaturated fatty acids include the n₃-series and the n₆-series. n₃-series polyunsaturated fatty acids are those where the first unsaturated double bond in the molecule appears after the third carbon atom. The n₆-series are those where the first unsaturated double bond in the molecule appears after the sixth carbon atom. The n₃-series includes linolenic acid, as well as long-chain eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The health benefits of these n₃-series fatty acids have received widespread attention in recent years.

In 1975, scientists claimed that although Eskimos had a high fat intake, their low incidence of cardiovascular disease was related to their high consumption of fish oil. Deep-sea fish oil is high in EPA and DHA. These two n₃-series long-chain polyunsaturated fatty acids have effects such as lowering blood triglycerides and preventing thrombosis, thus reducing the risk of cardiovascular disease. There is also evidence that EPA and DHA can prevent degenerative changes during the aging process.