Unsaturated Fats: Types, Health Benefits and Sources
Unsaturated fats are a type of fat that has at least one double bond in the fatty acid carbon chain. Depending on the number of double bonds between carbon atoms in the molecule of a fatty acid, they are classified into mono- and polyunsaturated fats. The primary sources of unsaturated fat are plant and nut oils. Unsaturated fats do not raise levels of “bad” LDL cholesterol, but they often tend to increase levels of “good” HDL cholesterol.
Fat is a nutrient that is essential to keeping the body properly functioning. Fat is a source of energy, it helps transport fat soluble vitamins, protects the body from cold and injury, protects vital organs, it is a building block of cell membranes and eicosanoids (these compounds help regulate the circulatory system) and is necessary for healthy development of many organs.
However, a diet high in fat can be bad for a person’s health. People who consume too much fat are at risk of obesity, which may contribute to various chronic conditions. Consuming large amounts of certain types of fat can also significantly raise a person’s overall cholesterol level, as well as raising the level of harmful cholesterol (low-density lipoprotein, or LDL, cholesterol).
Fats are made up of fatty acids (which are both saturated and unsaturated) and glycerol. For a fat to be classified as unsaturated, it must contain at least one double bond in the fatty acid carbon chain. This means there are at least two carbon atoms in the fatty acid chain that are not saturated with hydrogen (those forming the double bond).
Compared to saturated fats, unsaturated fats have a lower melting point and are therefore more likely to be in a liquid state when kept at room temperature. Unsaturated fats are also more likely to spoil more rapidly.
However, unsaturated fats happen to be the healthiest type of dietary fat. They reduce the levels of both total cholesterol and LDL cholesterol, while raising the levels of helpful HDL cholesterol. Despite that, people are urged to consume unsaturated fat in moderation, because excess calories from consuming large amounts of any type of fat can lead to weight gain. Dietary fat intake should not make up more than 35% of a person’s total daily calories.
Types of Unsaturated Fats
There are two types of unsaturated fats. The difference between the two is in the chemical structure:
- Monounsaturated fat. Though liquid at room temperature, monounsaturated fat may solidify when placed in the refrigerator. Monounsaturated fat is made up of triglycerides in which most of the fatty acids are monounsaturated, meaning they have only one double bond between carbon atoms in each fatty acid carbon chain. An example is olive or canola oil.
- Polyunsaturated fat. It is usually liquid both at room temperature and in the refrigerator. When exposed to oxygen, polyunsaturated fats tend to become rancid more readily than monounsaturated fats. Polyunsaturated fat is made up of triglycerides in which most of the fatty acids are polyunsaturated, meaning they have two or more double bonds between carbon atoms in the fatty acid carbon chain. Sunflower or soybean oil is an example.
Sometimes, monounsaturated and polyunsaturated fats may need to be partially hydrogenated to make them more solid and resistant to spoilage (e.g., margarine, shortening). In this process, hydrogen molecules are added and the number of double bonds is reduced. The fats thus become more saturated. Fats created through partial hydrogenation of unsaturated fat are called trans fats. These harmful fats have been shown to raise cholesterol levels in ways similar to saturated fats.
Potential Health Benefits of Unsaturated Fats
Consuming unsaturated fats in place of saturated fats can help to decrease total cholesterol and LDL cholesterol levels. Because of this, unsaturated fats help prevent fatty deposits (also known as plaques) from building up in the arteries, thus lessening the risk of heart attack and stroke.
Moreover, monounsaturated fatty acids may help raise the levels of HDL, the so-called “good” cholesterol. HDL cholesterol (HDL stands for high-density lipoprotein) carries cholesterol from the blood back to the liver. The liver then breaks down the cholesterol so that it can be eliminated from the body. This prevents excess cholesterol from being deposited as plaque in the arteries.
When it comes to decreasing the risk of coronary artery disease, a type of polyunsaturated fat known as omega-3 fatty acid appears to be particularly healthful. Omega-3s lower levels of both total cholesterol and triglycerides (a type of fat found in blood). Research suggests that these polyunsaturated fatty acids prevent blood platelets from clotting and sticking to artery walls, thus helping to prevent hardening of the arteries, reducing blood pressure levels and helping to protect the body against irregular heartbeats. These beneficial effects may eventually help reduce the risk of blocked blood vessels, heart attacks and strokes.
Another polyunsaturated essential fatty acid known as omega-6 also appears to decrease the risk of cardiovascular disease and reduce LDL-cholesterol levels. However, several studies have shown that dietary omega-6 fatty acids compete with omega-3s for incorporation into cell membranes. A diet high in omega-6s relative to omega 3s may thus be associated with lowering the body’s ability to fight inflammation and increasing the risk of certain diseases. Therefore, some experts are suggesting that people consume omega-6 fatty acids in a ratio of 1:1 with omega-3s. In a typical western diet this ratio is 16:1.
Sources of Unsaturated Fats
Unsaturated fats are found in many plant foods and fish. Examples of good sources of monounsaturated fats include canola, olive, peanut, safflower and sesame oils, nuts such as almonds, cashews, peanuts and pecans, and avocados. Polyunsaturated fats can be found in corn, flaxseed, soybean and sunflower oils and fish and seafood.
Please refer to the bottom of this post for more information on different types of mono- and polyunsaturated fats, their sources and health benefits.