Health Effects of Different Types of Dietary Fats
Fat is one of three types of nutrients (along with protein and carbohydrates) that supply calories to the body. Oils are liquid fats and the two terms may be used interchangeably. In addition to being a major source of energy, fat provides numerous other benefits to the body such as protection and insulation. Fat is also involved in the processes that help regulate heart rate, blood pressure, blood clotting, blood vessel constriction and the functions of the nervous system.
But, too much fat, especially too much of certain types of fat, can be bad for your health. Consuming excess fat puts you at risk of obesity, which can contribute to a number of conditions, including diabetes, heart disease, gallstones, osteoarthritis, sleep apnea and other chronic diseases. A diet high in certain types of fat can raise the level of low-density lipoprotein (LDL) cholesterol, the so-called “bad” cholesterol. In fact, the type of fat or oil that you consume is as important to your health as the overall total amount of fat consumed.
Types of Dietary Fats
Fat is a chemical compound made of fatty acids and glycerol. Most fat is stored in the body in the form of triglycerides, which circulate in the blood along with cholesterol. The major types of fat include saturated fats, unsaturated fats (including mono- and polyunsaturated fats) and trans fats. All fats contain both saturated and unsaturated fatty acids. Fats and oils are classified as either saturated or unsaturated depending on the percentage of the most dominant type of fatty acid in the mixture.
The two major types of healthy fats are both unsaturated and they benefit the body by reducing the levels of the so-called “bad” cholesterol. These two types of unsaturated fats are:
- Monounsaturated fats. When only one pair of hydrogen atoms in the carbon chain is missing (thus forming one double bond), we speak of monounsaturated fats. These fatty acids have a lower melting point and are usually liquid at room temperature, but start to solidify at refrigerator temperatures. Monosaturated fats can be mostly found in foods of plant origin. They not only lower levels of “bad” low-density lipoprotein (LDL) cholesterol, but also raise the levels of high-density lipoprotein (HDL) cholesterol, known as “good” cholesterol, which has health benefits.
- Polyunsaturated fats. These are unsaturated fats that are missing more than one pair of hydrogen atoms in the carbon chain, thus forming more than just one single double bond. Polyunsaturated fatty acids have very low melting point, which makes them highly unstable and more susceptible to rancidity than monounsaturated and saturated fats. They are found in foods from plant origin and from fatty fish. There are several types of polyunsaturated fatty acids, classified by the location of the first double bond along the carbon chain. They include omega-3 fatty acids, omega-6 fatty acids and omega-9 fatty acids. Read the bottom part of this post for more details on health properties of different types of polyunsaturated fatty acids and their food sources.
The two major types of unhealthy fats are:
- Saturated fats. These fats have no double bond in the carbon chain which makes them very stable. Saturated fats are solid or hard at room temperature with high melting point. They are found mainly in animal fats but also in certain plant fats such as cocoa butter, coconut oil and palm oil.
- Trans fats. These fatty acids, also known as trans-unsaturated fatty acids, do not occur naturally in foods (except for very small amounts in some meat and dairy products), but they are a result of the manufacturing process called hydrogenation. During this process, hydrogen atoms are added to improve stability and increase the melting point of the vegetable fat. This makes these chemically altered fats solid and stable at room temperature. Trans fatty acids are present in deep-fried foods, baked goods, margarines and various other processed foods made with partially hydrogenated vegetable oils.
The aforementioned subtle differences in chemical structure of the four major types of dietary fat make a big difference when it comes to their health properties. Read this post to learn more about the effects of saturated and unsaturated fats on your health.
Health Impact of Dietary Fats
In spite of the growing attention given to the negative consequences of fat consumption, fat is an essential component of a healthy diet. Eating a completely fat-free diet is not healthy. Fat provides nine calories per gram, which is more than double the amount provided by carbohydrates and protein. However, fat is digested more slowly than carbohydrates and proteins. Therefore, consuming fat gives people a sense of fullness. This sense of satiety may help them prevent overeating.
In addition to providing energy for the body, fat is necessary for the production of cell membranes and eicosanoids. Eicosanoids are signalling molecules similar to hormones that help regulate heart rate, blood pressure, blood vessel constriction, blood coagulation and the nervous system.
Dietary fat also provides the body with fatty acids, and especially with essential fatty acids including linoleic acid and alpha-linolenic acid, which are necessary for good health. Essential fatty acids cannot be made by the body and can only be obtained through food. Fatty acids help control blood pressure, blood coagulation, inflammation and other vital body functions. They aid in the growth and development of infants, keep the brain and nervous system functioning properly and help maintain healthy hair and skin.
Fat also helps transport fat-soluble vitamins including A, D, E and K from food into the body. In addition, fat serves as part of all cell membranes, insulates the body, protects vital organs, makes up part of material that insulates nerves and enhances nerve conduction, provides a storehouse for the body’s extra calories and helps repel water from the skin.
People with low body fat or those who do not get enough fat from their diets may not fully absorb fat-soluble vitamins. This may deprive them of the benefits that help strengthen the immune system, protect vision, smooth the skin and keep reproductive organs functioning properly. Furthermore, a lack of dietary fat can stunt the growth and mental development in children.
However, not all fats are created equal and different types of fats have varying effects on health. For example, monounsaturated and polyunsaturated fatty acids have been shown to have a protective effect on heart health. They lower levels of both total blood cholesterol and low-density lipoprotein cholesterol (also known as “bad cholesterol”). Moreover, monounsaturated fatty acids raise the levels of the heart-healthy high-density lipoprotein cholesterol.
By contrast, consuming too much saturated fats and trans fats can contribute to health problems. These fats cause the liver to produce more low-density lipoprotein cholesterol, which increases the risk of hardening of the arteries. Higher levels of saturated fats and trans fats in the diet are also associated with a greater risk of stroke and certain types of cancer. However, paradoxically saturated fats happen to be associated with increased level of “good” high-density lipoprotein cholesterol (unlike trans fats which tend to decrease it). It goes without saying, though, that consuming excessive amounts of fats, whether saturated or unsaturated, can lead to obesity, which also increases the risk of many health problems.
Getting the Right Balance
Many people reduce their fat intake to lose weight, help control diabetes or improve heart health. However, eliminating all fat from the diet can lead to a deficiency of essential fatty acids and cause health problems.
In response to consumer demand for “healthy” foods, manufacturers have developed low-fat food products. Although lower in fat content, these products are not necessarily lower in calories. Since dietary fat provides flavor and texture to foods, many manufacturers increase the sugar and carbohydrate content of low-fat foods to enhance the taste and add volume which were lost through eliminating fats.
Another option for people wishing to reduce their fat intake is to choose foods that contain fat substitutes in place of fat. These food additives mimic the desirable qualities of fat, such as texture, taste and appearance, without adding as many calories. Foods with fat substitutes also contain less LDL cholesterol. Although all fat substitutes on the market are considered safe by the food safety authorities, their long-term health effects are not known. Therefore, low-fat or fat-free versions of foods that normally contain fat should not be viewed as a substitute for a healthy, well-balanced diet.
When it comes to healthy eating, emphasis should not be placed solely on reducing the fat in the diet but also on lowering saturated fats and minimizing or eliminating trans fat intake. These unhealthy fats should be replaced with monounsaturated and polyunsaturated fats.
In general, total dietary fat intake should make up between 20-35% of daily calories. Saturated fats and trans fats put together should be less than 10% of total daily calorie intake whereas monounsaturated fats should be up to 20% of total calorie intake and polyunsaturated fats up to 10%. In fact, trans fats should be minimized to the lowest possible level in a person’s diet. In addition, people at risk for coronary heart disease should limit consumption of saturated fat to less than 7% of total calories.
Where to Get More Information: Fat Facts from NHS