Polyunsaturated Fatty Acids
Polyunsaturated fatty acids are components of food that have multiple double bonds in their chemical structure. The group of polyunsaturated fatty acids includes essential fatty acids omega-3 (including alpha-linolenic acid) and omega-6 (including linoleic acid). These fatty acids need to be obtained through diet.
Fats with a high content of polyunsaturated fatty acids are liquid at room temperature and in the refrigerator 1. In the food industry, they can be hydrogenated to solidify them. This process involves changing the chemical structure by adding hydrogen atoms to double bonds, saturating the fatty acids and making them solid at room temperature (e.g., margarine).
Carbon, hydrogen, and oxygen atoms are arranged into a carbon-hydrogen chain known as fatty acids. Polyunsaturated fatty acids have two or more double bonds in their molecule. The double bonds are located between adjacent carbon atoms. Due to the double bonds, the carbon-hydrogen chain is not "saturated" with hydrogen atoms. Therefore, they are referred to as unsaturated fatty acids.
Depending on the position of the first double bond from the methyl end (CH3; also known as omega or n-end) of the carbon-hydrogen chain, the polyunsaturated fatty acids are classified into omega-3 and omega-6 fatty acids. The first double bond of omega-3 fatty acids is located between the third and fourth carbon atom. In omega-6 fatty acids, the first double bond is between the sixth and seventh carbon atom.
Double bonds result in kinks in the carbon-hydrogen chain, which affects the structure and physical properties of the fatty acids.
Types of polyunsaturated fatty acids
There are numerous naturally occurring polyunsaturated fatty acids. Below is a selection of polyunsaturated fatty acids found in plant-based foods:
|Polyunsaturated fatty acids||Carbon atoms : Double bonds|
|Linoleic acid (Omega-6)
(Foods high in linoleic acid)
|Alpha-linolenic acid (Omega-3)
(Foods high in alpha-linolenic acid)
|Gamma-linolenic acid (Omega-6)||18:3|
|Eicosapentaenoic acid (Omega-3)||20:5|
|Docosahexaenoic acid (Omega-3)||22:6|
Functions and Effects
Polyunsaturated fatty acids are components of the retina and cell membranes. In addition, essential fatty acids are needed for brain functions (the brain consists largely of polyunsaturated fatty acids) and cell growth 2.
Polyunsaturated fatty acids are also required for the formation of hormone-like substances called eicosanoids. These are involved in inflammatory reactions, blood pressure control, and platelet aggregation 3. They also function as neurotransmitters. By the way, eicosanoids also improve blood flow properties, allowing nutrients to reach cells more effectively.
It has been demonstrated that the fatty acids linoleic acid, alpha-linolenic acid, eicosapentaenoic acid, and docosahexaenoic acid (the latter two are derived from alpha-linolenic acid) together protect against coronary heart disease 4. Further studies show a lower risk of fatal heart disease in men due to polyunsaturated fatty acids 5. Omega-3 fatty acids have been shown to slightly decrease total and LDL cholesterol levels, likely by displacing saturated fatty acids from the diet 6. The data also suggest a slight increase in HDL cholesterol.
Docosahexaenoic acid and arachidonic acid (formed from linoleic acid) are the predominant fatty acids in the brain and retinal phospholipids. 7. They play an essential role in nerve conduction and vision.
Polyunsaturated fatty acids are also necessary for muscle movements. 8.
In addition, there is evidence that polyunsaturated fatty acids have positive effects on bones 9 10. The exact role of polyunsaturated fatty acids in muscle health and functional mobility is not yet fully understood by scientists. However, current findings suggest a link between higher omega-3 intake and greater muscle mass and improved performance in older adults 11.
Possible consumption of high amounts of polyunsaturated fatty acids promotes lean tissue (muscle tissue without fat) in healthy individuals 12.
Oxidation with oxygen exposure and high temperatures - with negative consequences
It is worth noting, according to scientific studies, that polyunsaturated fatty acids oxidize (lipid peroxidation) and become rancid more quickly at high temperatures 13. Alpha-linolenic acid is particularly sensitive to light, oxygen, and heat, which leads to its destruction and toxicity 14. According to scientists, alpha-linolenic acid is also destroyed 5 times faster than linoleic acid.
For this reason, cold-pressed oils should not be used for cooking and frying. If they are still used in warm cuisine, they should only be lightly heated. Oils with a high omega-3 fatty acid content, such as flaxseed oil, should be stored in the refrigerator.
Vitamin E as an antioxidant for polyunsaturated fatty acids
According to scientific studies, polyunsaturated fatty acids, such as omega-3, oxidize faster than saturated fatty acids 15 16. Polyunsaturated fatty acids are particularly vulnerable to damage caused by oxygen. This results in the formation of aggressive free radicals in the cells, which can harm health. To prevent the oxidation process in the cells, vitamin E is needed as an antioxidant 17 18.
Accordingly, the daily requirement of vitamin E also increases with a diet rich in polyunsaturated fatty acids. Scientists believe that for every gram consumed, at least 0.6 mg of vitamin E is needed 19. Therefore, it is important to ensure an adequate supply of foods and beverages rich in vitamin E.
Due to varying recommendations from health organizations, the intake recommendations for polyunsaturated fatty acids (PUFA) vary. For adults, they range from 6 to 10% (11% is recommended for 2- to 18-year-olds) 20.
The following values result from this for the daily intake of polyunsaturated fatty acids:
|Caloric needs||Upper limit of intake for polyunsaturated fatty acids -|
at 6% of daily energy needs
|Upper limit of intake for polyunsaturated fatty acids -|
at 10% of daily energy needs
|2,000 kcal||12.9 g||21.5 g|
|2,200 kcal||14.2 g||23.7 g|
|2,400 kcal||15.5 g||25.8 g|
|2,600 kcal||16.8 g||28.0 g|
|2,800 kcal||18.1 g||30.1 g|
|3,000 kcal||19.4 g||32.3 g|
During pregnancy and breastfeeding, it is important to ensure an adequate intake of essential fatty acids. Studies have shown that these fatty acids are needed for the brain development and body size of the fetus and infant 21. Maria Makrides, BSc, BND, PhD; Robert A. Gibson, BSc, PhD; Andrew J. McPhee, MBBS; Carmel T. Collins, RN, BSSc, PhD; Peter G. Davis, MBBS, MD; Lex W. Doyle, MBBS, MSc, MD; Karen Simmer, MBBS, PhD; Paul B. Colditz, MBBS, PhD; Scott Morris, MBBS, PhD; Lisa G. Smithers, BAppSc, PhD; Kristyn Willson, BSc(Hons); Philip Ryan, MBBS, BSc: Neurodevelopmental Outcomes of Preterm Infants Fed High-Dose Docosahexaenoic AcidA Randomized Controlled Trial; JAMA. 2009;301(2):175-182. doi:10.1001/jama.2008.945.; January 14, 2009, Vol 301, No. 2 22 23.
With a diverse vegan diet rich in fruits, vegetables, legumes, grains, nuts, and seeds, the needs for omega-3 and omega-6 can be well met. However, greater emphasis should be placed on a diet rich in omega-3 fatty acids, as an excess of linoleic acid and a deficiency of alpha-linolenic acid can have negative effects on health 24.
Vegans have higher intake levels of polyunsaturated fatty acids compared to the general population, as well as a better ratio of polyunsaturated to saturated fatty acids. 25.
If there is a deficiency of polyunsaturated fatty acids, symptoms such as poor concentration, depression, and dry skin may occur. There may also be disruptions to the liver and kidneys, impaired growth, and weakened immune system. 26.
Plant-based foods contain an adequate amount of healthy polyunsaturated fatty acids. Linoleic acid (Omega-6) is found in larger quantities in corn oil (53.2 g per 100 g), soybean oil (50.4 g), rapeseed oil (18.6 g), Brazil nuts (23.9 g), pumpkin seeds (20.7 g), and almonds (12.3 g).
Alpha-linolenic acid (Omega-3) is abundant in flaxseed oil (53.4 g), flaxseeds (22.8 g), chia seeds (17.8 g), hemp seeds (8.7 g), and rapeseed oil (9.1 g). Consuming just one teaspoon of flaxseed oil per day meets the daily requirement of alpha-linolenic acid.
To access the table of polyunsaturated fatty acids in food, click here.
Due to the diverse presence of healthy fats, studies show that vegans have the highest intakes of polyunsaturated fatty acids 27.
What should vegans consider?
It should be noted that the ratio of Omega-3 to Omega-6 fatty acids should be balanced to avoid negative health effects. Vegans often tend (unconsciously) to have a diet that is high in Omega-6 fatty acids since most plant-based foods contain more Omega-6 than Omega-3. This is also supported by scientific research conducted in the Netherlands comparing vegans to omnivores 28.
Therefore, the focus should be on a diet that is rich in Omega-3 fatty acids. Recommended oil for cooking is cold-pressed rapeseed oil. Otherwise, whenever possible, opt for healthy flaxseed oil! Do not heat flaxseed oil as it can produce toxic substances.