Fat is one of the three major macronutrients that make up the bulk of the nutrition in our food, along with carbohydrates and protein. Micronutrients – individual vitamins and minerals – are needed in much smaller amounts.
Fat is an essential part of our diet. Our bodies need fat as an additional source of energy when carbohydrates are not available. Fat has double the amount of calories that is found in carbohydrates or protein and is a concentrated source of energy. Fat also helps with the absorption of the fat-soluble vitamins, such as vitamins A, D, E and K. Fat cells help to keep us warm by insulating the body and sustaining a normal core body temperature. Fat is needed to build the exterior part of cells in the body, called the cell membrane, as well as the sheaths that surround nerves.
Food provides unsaturated, saturated, and trans fats. Each of these types of fat is processed differently by the body. The dietary effects of different fats and oils on the body – on cardiovascular health in particular – have been studied extensively over the years. Both “good” (healthy) and “bad” (unhealthy) fats are hiding in your food. But how do you tell them apart and which ones should you avoid?
Good fats – unsaturated fat
Good fats are heart-healthy fats that stabilize cholesterol levels and lower the risk of cardiovascular disease. The only good fat is unsaturated fat that is primarily found in plant foods and is liquid at room temperature. It comes in two versions, of which monounsaturated fat as found in olive oil is deemed to be healthier than polyunsaturated fat found in other plant based oils, such as sunflower and canola oil.
Monounsaturated fat, as found in olive oil, can reduce the levels of unhealthy LDL (low density lipoproteins) cholesterol and maintain or even increase the levels of healthy HDL (high density lipoproteins) cholesterol. Monounsaturated fat is particularly resistant to oxidation. Olive oil contains more natural antioxidants than any other plant based oil.
Polyunsaturated fat is the main constituent of seed oils, such as peanut, sunflower, canola oils, etc. This type of fat may decrease the levels of both LDL and HDL cholesterol in the bloodstream. Use should be limited to low essential levels as polyunsaturated fat are more prone to oxidation and not only use up the desirable antioxidants in the fat, but can result in the formation of undesirable free radicals. Oxidized LDL’s contributes to plaque build-up in the arteries. LDL’s that contain high levels of omega 6 – of which high concentrations are found in polyunsaturated fat – are particularly prone to oxidation. The build-up of plaque happens when LDL particles penetrate arterial walls, where they become oxidized and are attacked by white blood cells, resulting in inflammation.
(Just like a sliced apple discolors due to exposure to oxygen, some health problems stem from the effect of oxygen on the body. Oxygen can be destructive to the cells in the body when free radicals (unstable molecules) are formed that subject the cells to continuous damage, known as oxidative stress or oxidation. This process causes damage to the body such as making us age faster, converting healthy cells into cancerous ones, elevating blood pressure, hardenings of the arteries, and promoting inflammation. Nutrients called antioxidants help the body repair cell damage due to free radicals.)
Bad fats – saturated and trans fats:
Bad fats include animal and plant based saturated fats, as well as industrial-made trans fats. Research conducted during the late 1990’s –which later proved to be flawed – has linked the consumption of saturated fat with increases in blood cholesterol levels and an increased risk of heart disease. These (flawed) findings have resulted in the official “low-fat’ dietary guidelines in the USA at the time, which was adopted in other countries as well.
Saturated fat, according to the latest studies, is not inherently harmful when used in moderation, but has been linked to an increase in some risk factors for heart disease. Saturated fat is solid at room temperature and most comes from animal sources, for example in beef, mutton, poultry, milk, cheese and butter. Some saturated fats are plant based and easily distinguished as they are also solid at room temperature, such as coconut, palm and palm kernel oils. Saturated fat tend to increase the levels of bad LDL and decrease the levels of the healthy HDL cholesterol particles in the bloodstream. The American Heart Foundation recommends that saturated fat intake should be limited to no more than 7% of your daily calories, while the American Diabetes Association suggests a daily intake of no more than 15 grams of saturated fat per day.
Trans fats are the worst type of dietary fat with high risks for cardiovascular health. This type of fat is formed during industrial processes, such as during the manufacturing of margarine and spreads from plant based oils. Trans fat is produced when liquid oil is converted into solid fat. Hydrogenation processes are used to turn oils into solids and to prevent them from becoming rancid. (When an organic compound is hydrogenated, it becomes more “saturated” with hydrogen atoms.) Apart from increasing the bad LDL cholesterol levels, trans fats also affect the body’s immune system and trigger inflammation. Oxidised LDL’s are the main cause of lesions and plaque build-up in the arteries. Trans fats are found in fast foods, while most processed and baked foods are made with the trans fat containing hydrogenated oil. The American Heart Foundation recommends that trans fat intake should be limited to less than 1% of total calories.
Cholesterol:
Saturated fat and trans fat, unlike unsaturated fat, raise the levels of lipoproteins in the blood. Higher numbers of LDL particles in the blood raise the risk of these particles passing into artery walls, becoming oxidized, inflamed and leading to plaque formation. Not only the number of particles, but also the size of the particles affect this process. Any proper cholesterol test should not only determine total cholesterol, but also the number of the particles, which may differ from person to person. The smaller and denser the particles, the easier to penetrate arterial walls, while bigger particles will float along in the bloodstream and are less prone to cause damage. This means that in order to more accurately predict the risk of heart disease, the number of LDL particles matters more than the total amount of LDL cholesterol in the bloodstream. (Higher numbers of LDL in relationship with total cholesterol indicate smaller particles.)
The “good” HDL particles remove cholesterol from arteries and plaque. That is why the ratio between LDL and HDL particles plays an important role in determining the risk of heart disease.
Conclusion:
Contrary to common belief, it is not fat as such that makes you fat, but rather overindulging in any kind of fat (or carbohydrates or proteins) that increases your calorie intake over and above energy output, and put you at risk for becoming overweight, making you prone to adverse health conditions such as heart disease, high blood pressure and diabetes.
From a long term health perspective, it is clear that some fats are healthier than others. In this regard, olive oil is simply the best choice, as it is monounsaturated, high in antioxidants, and can be used for cooking, baking or as a salad dressing. Extra virgin olive oil should be the only oil allowed in your kitchen.
Sources:
The truth about fats: The good, the bad and the in-between. Published online and updated 13 August 2018. Harvard Medical School. (www.health.harvard.edu)
Is saturated fat bad for your health? Evidence-based analysis published online and updated 22 October 2018. Examine. (www.examine.com)
The larger role of macronutrients. Published July 2019. Harvard Men’s Health Watch. Harvard Medical School. (www.health.harvard.edu)
Does consumed fat get converted to fat in the body? Published online and updated 6 December 2018. Healthy Eating, SFGate. (www.sfgate.com)
Three functions of fat in the body. Published online and updated 12 December 2018. Healthy Eating, SFGate. (www.sfgate.com)
Saturated vs unsaturated fats in lipids. Published online and updated 12 December 2018. Healthy Eating, SFGate. (www.sfgate.com)
Unhealthy fats list. Published online and updated 27 December 2018. Healthy Eating, SFGate. (www.sfgate.com)
Ask the doctor: How do trans fats harm health? Published online December 2013. Harvard health Letter. Harvard Medical School. (www.health.harvard.edu)
HEALTH INSIGHT.
July 2019