Monounsaturated versus Polyunsaturated Fats
February 02, 201901,551

Which Fats are Healthier for You? Monounsaturated vs. Polyunsaturated Fats

Introduction to Fats and Types of Fats

Fat is a type of nutrient found in food.1 It can be found in both plant and animal food sources.2 It is classified as a macronutrient, because its main function is to supply energy to the body.3

Fat is notoriously known as the macronutrient that supplies the most energy to the body. When we consume more energy than what our body needs, this excess energy is stored as body fat. For this reason, people who are trying to lose weight will often follow low-fat diets.4

Despite its potential to cause weight gain, fat also has several essential functions in the body:

  • Fat is one of the main building blocks in cell membranes – the vital protective walls around body cells.4
  • It is also one of the main components of the insulating sheaths around nerve cells – the transmitters of messages from the brain to the body and vice versa.4
  • It is essential for the absorption of fat-soluble vitamins – vitamin A, D, E and K – without it, these vitamins cannot be absorbed and deficiencies may develop.2
  • It is needed for blood clotting, inflammation and muscle movement.4
  • It helps to regulate the levels of good and bad cholesterol in the blood.3

There are various types of dietary fats. All fats are made up of a basic chain of carbon atoms linked to hydrogen atoms, but these chains can differ in length and shape. These small differences in structure can have a big impact on how the fats function in the body. Some fats have a positive effect on the body, whilst others can have a negative effect in the long-term.4

There are four main types of fats:

  • Saturated fat – this type of fat comes mainly from animal food sources, namely red meat, full-fat dairy products and poultry. Its chemical structure has no carbon-to-carbon double bonds in it, which means it cannot take on anymore hydrogen atoms – it is “saturated”. This structure makes it solid at room temperature.3
  • Trans saturated fat – this type of fat is formed when hydrogen is added artificially to vegetable oils. This is known as hydrogenation – a food processing technique used to make vegetable oils more solid at room temperature. Hydrogenation prevents vegetable oils from going rancid. Trans fats can be found in most commercially baked products, such as cookies and pastries, as well as fast foods.4
  • Monounsaturated fat – this type of fat comes mainly from plant food sources. It is known as a “monounsaturated” fat because it contains one carbon-to-carbon double bond in its structure. “Mono” means one and “unsaturated” means that it has the potential to take on more hydrogen atoms. This makes it liquid at room temperature.4
  • Polyunsaturated fat – this final type of fat also comes mainly from plant food sources, however, it differs from monounsaturated fats in that it has two or more carbon-to-carbon double bonds in its structure – “poly” means many. It is also liquid at room temperature. There are two main types of polyunsaturated fats – omega 3 and omega 6. These are both known as essential fatty acids, meaning that the body cannot make them itself, but has to get them from food sources.4

All dietary fats contain a mix of polyunsaturated fats, monounsaturated fats and saturated fats in different proportions. For example, butter is mostly saturated fat, but it also contains some unsaturated fats. Most plant oils are high in unsaturated fats, but also contain small amounts of saturated fat.2


Good Fats: What are Healthy Fats?

Some fats may have positive effects on our bodies in the long-run, whereas others may have negative effects. The fats that have a positive effect on our bodies generally come from vegetables, nuts, seeds and fish.4

What makes a fat healthy has a lot to do with its structure on a chemical level. Healthy fats generally have fewer hydrogen atoms bonded to their carbon atoms, which results in one or more double carbon-to-carbon bonds. In other words, they are “unsaturated”. Healthy fats are also generally liquid at room temperature. There are two main groups of healthy fats – monounsaturated and polyunsaturated fats.4


Health Benefits of Good Fats

Healthy fats can have numerous health benefits. One of the benefits of eating healthy fats is that they may keep your blood cholesterol levels in balance. They are capable of decreasing the level of LDL (bad cholesterol) and increasing the level of HDL (good cholesterol) in the blood. Replacing unhealthy fats with healthy ones can help to lower your risk of developing heart disease.5

Both monounsaturated and polyunsaturated fats are also good sources of vitamin E.2 Vitamin E is an antioxidant, which means that it prevents free radicals from damaging body cells. This can decrease the risk of developing conditions related to aging. Vitamin E is also important for the functioning of the immune system and the formation of red blood cells. It also helps to widen blood vessels, which is necessary to prevent blood clotting and, subsequently, heart attacks and strokes.6

Monounsaturated and polyunsaturated fats both have a positive effect on insulin resistance, which is likely to decrease the risk of developing type two diabetes. This is mostly beneficial if they are eaten in place of unhealthy fats in the diet, not in addition to them.7

Polyunsaturated fats provide essential fatty acids – omega 3 and omega 6. These fatty acids have numerous health benefits and roles in the body, but they have to be obtained from the foods you eat, because your body cannot make them itself .8

Health benefits of eating omega 3 fatty acids4:

  • Omega 3 fatty acids can be used to treat or prevent stroke and heart disease.
  • They can also decrease blood pressure, increase HDL, decrease triglycerides and prevent lethal heart rhythms.
  • They may also reduce the need to use corticosteroid medications if you have rheumatoid arthritis.

Health benefits of eating omega 6 fatty acids5:

  • Omega 6 fatty acids can help to improve blood cholesterol levels (increase HDL and lower LDL).
  • They may also reduce the risk of developing heart disease.


Best Sources of Monounsaturated Fats

Most foods contain a combination of different fats, but the highest source of monounsaturated fat is usually found in plant oils9:

  • Olive oil
  • Safflower oil
  • Peanut oil
  • Canola oil
  • Peanut oil

Other foods that are high in monounsaturated fats include:

  • Avocados9
  • Peanut butter9
  • Nuts (almonds, hazelnuts, pecans and peanuts)10
  • Seeds (pumpkin and sesame seeds)10
  • Mayonnaise and oil-based salad dressings10
  • Soft margarines10

Good Sources of Polyunsaturated Fats

Some plant oils are good sources of polyunsaturated fats9:

  • Corn oil
  • Soybean oil
  • Sunflower oil

Other foods that are good sources of polyunsaturated fats include:

  • Tofu9
  • Soybeans9
  • Fish (herring, mackerel, trout, salmon and tuna)10
  • Nuts (pine nuts and walnuts)10
  • Soft margarines10
  • Mayonnaise and oil-based salad dressings10

In-between Fats

The Western diet is often quite high in saturated fats. Most animal products contain saturated fats, such as red meat, poultry, full-fat dairy products and cheese, as well as a few tropical plant oils4 – coconut oil, palm oil and palm kernel oil.2

Saturated fats cause the liver to produce more cholesterol, 8 but they tend to increase bad (LDL) cholesterol slightly more than healthy (HDL) cholesterol. The balance of good-to-bad cholesterol may therefore be off-set by eating too much saturated fat. When your level of LDL cholesterol becomes too high, it begins to block the arteries of your heart and other parts of your body. Blocked arteries can lead to heart attacks or strokes. 4

Recently, there has been debate around whether saturated fat is actually bad for us or not. This debate started when a meta-analysis was published in 2010 stating that “there was no significant evidence for concluding that dietary saturated fat was associated with an increased risk of Coronary Heart Disease (CHD) or Cardiovascular Disease (CVD).”11

Later on, this statement was challenged by results from other studies. They found that if saturated fat is replaced with polyunsaturated and monounsaturated fats, rather than very processed carbohydrates, the risk of heart disease is decreased.2,11


Bad Fats

This final type of dietary fat has the worst impact on our health. It is known as trans fat and it is not usually found naturally in foods. Trans fats are mainly produced artificially and the most common food source of trans fat is partially hydrogenated vegetable oil.8

Trans fat is found in commercially-produced fried foods and commercially baked products, such as doughnuts, pizza crusts, cakes, pastries, crackers, pie crusts and hard margarines or spreads.8

Trans fat was first produced by food manufacturers to reduce the cost of food production and increase the shelf-life of their food products. Many fast food outlets and restaurants prefer using oil that contains trans fat because it can be used to fry foods repeatedly in commercial fryers.8


Consequences of Bad Fats

Trans fats increase the levels of bad (LDL) cholesterol in the blood and decrease the levels of good (HDL) cholesterol. This may lead to heart disease. According to Harvard Medical School, “for every 2% of calories from trans fat consumed daily, the risk of heart disease rises by 23%.”8

Trans fats are also capable of increasing inflammation in your body. This can cause chronic diseases, such as heart disease, stroke and diabetes.8

Insulin resistance can also be worsened by eating trans fat. This means that trans fat could increase your chance of developing type two diabetes.8


Practical Tips for Including Healthy Fats in your Daily Diet

The 2015-2020 Dietary Guidelines for Americans suggests the following11:

  • Avoiding trans fat.
  • Limiting saturated fat to less than 10% of your calorie intake per day.
  • Replacing saturated fat with heathier unsaturated fats.

Just a word of caution, even healthy fats are high in calories, so don’t eat an excess amount of them. The goal is to replace saturated fats with healthier fats, not to include larger portions of healthy fats.11

From a practical perspective, how can you go about following these guidelines? The following tips may help you:

  • Check food labels for the amount of trans fat contained in the food products you eat. Also look for the word “partially hydrogenated” in the ingredients list, as foods containing less than 0.5 grams of trans fat are legally allowed to record the amount of trans fat as 0 grams.11
  • Switch out the solid fats that you use in frying or baking for oils rather.11
  • Try to eat fish at least two to three times a week (100 – 150 gram servings)5 and bake or broil it rather than frying.11
  • Try to choose leaner meats and skinless poultry where possible. It is also healthier to remove any visible fat off meat before cooking it, including chicken skin.11
  • Be cautious about the types of snacks you choose – check the labels of snacks for trans or saturated fats. It is healthiest to snack on whole fruits, vegetables11 and nuts.12
  • Add olive oil, avocado, nuts and seeds to your salads instead of cream-based salad dressings.13
  • Try using soft margarines that are high in plant oils rather than butter or hard margarines on bread.13 If you don’t like margarine, you can use spreads like hummus, nut butters or avocado.
  • Try to switch out meat and poultry with fish and plant-based proteins.10
  • When eating out, you could ask the waiter to find out which fats are used in the preparation of your meal and request that unsaturated fats be used where possible.8
  • Try to use healthier cooking methods, such as grilling, roasting, baking or steaming, rather than frying.8
  • Choose low-fat or fat-free dairy products wherever possible.8
  • Add nuts and seeds to your breakfast cereals, oats or yogurt in the mornings.5
  • Choose wholegrain breads containing seeds.5

Should I be following a low fat diet?

Low fat diets may be effective for weight loss, but healthy fat serves many useful functions in your body.4 Following a diet that is too restrictive of healthy fat may cause:

  • Deficiencies of fat-soluble vitamins (vitamin A, D, E and K).2
  • Decreased functioning of your immune system.6
  • Decreased insulation of your vital organs, which may make you more susceptible to getting sick.3
  • Poor regulation of blood cholesterol levels, which may increase your risk of heart disease.4
  • Increased risk of developing inflammatory diseases, such as hypertension and heart disease.6
  • Increased susceptibility to conditions caused by aging.6
  • Increased risk of developing insulin resistance and, in turn, type two diabetes.7

It is therefore best not to restrict fat too much when you are trying to lose weight. Including moderate amounts of healthy fats, as part of a balanced diet, is the best option for your health.4


  • Why are saturated fats bad?
    • Eating too much saturated fat can off-set the balance of good-to-bad cholesterol in your blood.4
    • This can cause the arteries in your heart and other body parts to become blocked, which may lead to heart attacks or stroke.4
  • What are good fats for weight loss?
    • No particular fat is good for weight loss – all fats are equally high in calories.11
    • Healthy fats can improve your heart health, but if they are eaten in excess amounts, they can cause weight gain.11
    • It is best to replace unhealthy fats with healthier unsaturated fats, rather than eating more of them.11
  • What are healthy fats for bodybuilding?
    • All fats contain concentrated amounts of energy, which your body can use to build up muscle tissue provided that enough protein is eaten too.14
    • Different dietary fats do not effect muscle building very differently14, however, unsaturated fats are healthier choices for your overall health.5
  • What is the difference between good fat and bad fat?
    • The difference between healthy and unhealthy fats has a lot to do with their chemical structure.4
    • Fatty acids that have double carbon-to-carbon bonds in their structure are “unsaturated”, because they have the capability to take on more hydrogen atoms.4
    • Fatty acids that have no double bonds in their structure are “saturated”, because their carbon atoms cannot bond to anymore hydrogen atoms.4
    • Unsaturated fatty acids have been linked to numerous health benefits, such as decreased bad (LDL) cholesterol, increased good (HDL) cholesterol, decreased inflammation in the body and decreased risk of heart disease, diabetes and hypertension.4,5
    • Saturated fatty acids have been linked to the opposite effects – an off-set balance of good-to-bad cholesterol and subsequent increased risk of heart attacks and stroke.4
    • Trans fatty acids are hybrids – unsaturated fatty acids which have had hydrogen added to them to make them solid at room temperature. This process turns a healthy fat into an unhealthy fat. In fact, trans fats increase bad (LDL) cholesterol, triglycerides in your blood and overall inflammation in your body. This increases your risk of heart disease, diabetes and hypertension.8


  1. Dietary Fats. Last updated May 25, 2015.
  2. United States Department of Agriculture. Dietary Guidelines for Americans 2015 – 2020. Published December 2015.
  3. Mayo Clinic. Nutrition and healthy eating. Last updated February 02, 2016.
  4. Harvard Health Publishing. The truth about fats. Last updated August 22, 2017.
  5. Heart Foundation. Monounsaturated and polyunsaturated (omega 3 and omega 6) fats.
  6. Vitamin E. Last updated September 05, 2017.
  7. NIH Public Access. Dietary fats and prevention of type 2 diabetes. Published January 2009.
  8. Heart Insight. Is Fat Good for Us or Bad? Yes. Published in Fall, 2017.
  9. American Heart Association. Monounsaturated Fat. Last updated March 24, 2017.
  10. Food and Drug Association. Monounsaturated and Polyunsaturated Fats.
  11. Mayo Clinic. Nutrition and Healthy Eating. Last updated February 02, 2016.
  12. Facts about Monounsaturated fats. Accessed September 05, 2017.
  13. University of Illinois Extension. What are Polyunsaturated and Monounsaturated Fats? Last updated June, 2014.
  14. Helms ER, Aargon AA, Fitschen PA. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. Journal of the International Society of Sports Nutrition 2014, 11:20


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