Types and differences of fats & oils

Fats are made of fatty acids (chains of carbon, hydrogen and oxygen) and glycerol (three-carbon alcohol that forms the backbone of fatty acids). Most fat is stored in the body as triglycerides, which circulate in the blood along with cholesterol. (The term “triglycerides” can also refer to the common form of fat in foods as well as the body.)

The major types of fat include saturated fats, unsaturated fats and trans fats. All fats and oils contain both saturated and unsaturated fatty acids. Fats are classified as either saturated or unsaturated depending on the percentage of fat that is dominant. For example, butter contains mostly saturated fat as well as lesser amounts of unsaturated fat. As a result, it is classified as a saturated fat. Meanwhile, canola oil has a high percentage of monounsaturated fat, as well as smaller amounts of polyunsaturated and saturated fats. It is classified as a monounsaturated fat.

The two major types of healthy fats are both unsaturated. These fats reduce levels of low-density lipoprotein (LDL) cholesterol, the so-called “bad” cholesterol. The two major types of unsaturated fats are:

• Monounsaturated fats. A form of unsaturated fat that is missing one pair of hydrogen atoms in the carbon chain, forming one double bond. Extra hydrogen atoms can be inserted chemically, which is why they are called “unsaturated.” These fatty acids are found mostly in foods from plant origin, have a lower melting point and are usually liquid at room temperature, but start to solidify at refrigerator temperatures. Monounsaturated fats not only lower levels of “bad” cholesterol, but also raise the levels of high-density lipoprotein (HDL) cholesterol, which has health benefits. Sources of monounsaturated fats include canola, olive and peanut oils, and avocados.
  
  

  

• Polyunsaturated fats. An unsaturated fat that is missing more than one pair of hydrogen atoms in the carbon chain. The presence of more double bonds between the carbon atoms lowers the melting point even more than monounsaturated fats. Polyunsaturated fatty acids are highly unstable and are more susceptible to rancidity than saturated and monounsaturated fats, especially after prolonged contact with oxygen, light, or heat. Found in foods from plant origin and from fish, polyunsaturated fats can be further divided into two sub-groups depending on the location of the first double bond along the carbon chain: omega-6 fatty acids and omega-3 fatty acids. Polyunsaturated fats are found primarily in oils from plants, including sesame and sunflower seeds, corn and soybeans, many nuts and seeds and their oils, as well as fatty fish such as salmon.

The two major types of unhealthy fats include:

• Saturated fats. Fats in which every available site along each carbon chain is filled with a hydrogen atom. Saturated fatty acids are found mainly in animal fats (e.g., butter, lard, whole milk) and certain plant fats (e.g., coconut oil, palm oil, cocoa butter). They have a high melting temperature because of their chemical structure and are solid or hard at room temperature.
  
  
• Trans fats. A form of unsaturated fat in which hydrogen atoms are added during a process called hydrogenation. Trans fatty acids are mainly manufactured fats that are stable and solid at room temperature. Trans fats are found in deep-fried foods, margarines, baked goods and other processed foods made with “hydrogenated” or “partially hydrogenated vegetable oils.” Some trans fat is found naturally in small amounts in various meat and dairy products.

These subtle chemical differences between the types of fats are responsible for their very different properties and effects in the body. Diets high in saturated fats and trans fats increase low-density lipoprotein (LDL) or “bad” cholesterol levels and, therefore the risk of heart disease, whereas most unsaturated fats have harmless or even helpful effects on blood cholesterol.

All fats are a mixture of saturated, polyunsaturated and monounsaturated fatty acids. However, the dominant form of fatty acid determines which of these categories a fat belongs to. For example, olive oil, safflower oil and canola oil are high in monounsaturated fat content and are considered to be monounsaturated fats. Meanwhile, butter, animal fats, and tropical oils such as palm oil and coconut oil are high in saturated fat content and are considered to be saturated fats.