VEGANALYZE

Linoleic Acid

Linoleic acid is a polyunsaturated fatty acid. Since it cannot be synthesized by the body, linoleic acid is considered an essential fatty acid. Fats high in linoleic acid remain liquid at room temperature.

The name of the fatty acid is derived from the Greek word for flax (linon) and the Latin word oleum, which means oil or derived from oil.

Chemical Structure

Linoleic acid (18:2n-6) consists, like other fatty acids, of a hydrocarbon chain. In the case of linoleic acid, this chain consists of 18 carbon atoms and has two cis-double bonds in its structure. In a cis-configuration, the hydrogen atoms on the carbon atoms of the double bond are positioned on the same side. The first double bond starts from the methyl end (also known as the omega end) between the sixth and seventh carbon atoms. This is why linoleic acid is referred to as an omega-6 fatty acid.

Function

Linoleic acid is a component of the epidermis (outer layer of the skin) 1. It is required there as a building block of ceramides for regulating the skin's water balance and simultaneously protecting it from drying out.

In addition, linoleic acid can also be used as an energy source as needed. The body can also convert it into triglycerides, cholesterol, and phospholipids (components of cell membranes) 2.

Linoleic acid is converted into other fatty acids

In the body, linoleic acid is converted into gamma-linolenic acid (GLA) by the enzyme delta-6 desaturase (FADS2). Subsequently, gamma-linolenic acid is further converted into dihomo-gamma-linolenic acid (DGLA) and then into arachidonic acid (AA). The estimated conversion rates of linoleic acid to arachidonic acid range from 0.3% to 0.6% 3.

DGLA and AA are used to produce a series of eicosanoids (leukotrienes, prostaglandins, and thromboxanes), which act as neurotransmitters and are involved in influencing immune responses.

Lower risk of heart disease and mortality due to linoleic acid

Scientists have found that older individuals with a high plasma level of linoleic acid have a lower risk of mortality compared to those with a lower level 4 5.

In studies from 2014, the intake of linoleic acid has been associated with a reduction in the risk of coronary heart disease 6. Compared to those with the lowest intake, individuals with the highest linoleic acid consumption had a 15% lower risk of coronary heart disease (CHD) and a 21% lower mortality risk caused by CHD. Furthermore, this study confirms recommendations from other scientific investigations to replace saturated fatty acids with polyunsaturated fatty acids to prevent heart disease.

Other findings also link linoleic acid inversely with overall and coronary mortality in older adults 7.

Linoleic Acid Improves Cholesterol Levels

Linoleic acid is the most important dietary fatty acid needed for regulating LDL cholesterol levels by downregulating LDL cholesterol production and improving its transport 8. Furthermore, linoleic acid has a positive impact on healthy HDL cholesterol concentrations in the body 9.

Minimizing Breast Cancer Risk with Linoleic Acid

The results of a study summary involving 358,955 women (including 10,410 with breast cancer) from 2015 indicate a reduced breast cancer risk (1 to 3%) for both dietary and plasma linoleic acid 10. The risk decreased by 1% per 10 g of linoleic acid consumed per day.

Requirement

With a balanced vegan diet, it's easy to meet the linoleic acid requirement.

An omega-3 to omega-6 ratio of 1:1 to 1:4 is associated with optimal health benefits 11. Vegans can use the following values for omega-6 as a reference. These values were derived by us based on the recommended omega-3 requirements for vegetarians (no recommendations were issued specifically for vegans):

Deficiency

A deficiency of linoleic acid is highly unlikely with a varied vegan diet. If a deficiency occurs, it can manifest as dry skin and rash. 12. Furthermore, a deficiency also leads to reduced formation of gamma-linolenic acid, dihomo-gamma-linolenic acid, and arachidonic acid, which can result in metabolic disorders.

Linoleic acid, found in breast milk, is necessary for infant development. A deficiency can cause scaly skin, growth delays, altered plasma fatty acid patterns, and thrombocytopenia. 13.

Excess - to be considered by vegans

There are concerns that increased consumption of linoleic acid may lead to increased production of arachidonic acid, resulting in the formation of more pro-inflammatory eicosanoids that could be detrimental to heart health, potentially leading to an increase in heart diseases and mortality risk. 14 15. Practical evidence from controlled intervention studies in healthy individuals shows that increased dietary intake of linoleic acid does not result in an increase in inflammatory markers 16.

A critical and scientific review from 2013 on the general impact of linoleic acid on bodily inflammation demonstrates significant cardiovascular benefits when consuming linoleic acid in its natural form, rather than processed form (industrially processed) 17. According to the study, unprocessed linoleic acid should be consumed as part of a healthy diet. It is associated with a reduction in inflammation and reduced cardiovascular risks. In contrast, altered forms of linoleic acid are atherogenic (causing arteriosclerosis) and should be avoided. Depending on the food source and form of linoleic acid, this can have implications for cardiovascular health.

Other study findings suggest a link between higher consumption of linoleic acid and the oxidation of LDL cholesterol (causing cholesterol to become rancid and unusable), platelet aggregation (clumping of blood platelets), and impaired uptake of essential fatty acids into cell membrane phospholipids 18.

According to a 2012 study, an excess of linoleic acid during pregnancy can have a negative impact on the omega-3 levels of the developing fetus (see omega-3 deficiency) 19.

Excess linoleic acid also hinders the conversion of alpha-linolenic acid into eicosapentaenoic acid and docosahexaenoic acid. Alpha-linolenic acid and linoleic acid compete for absorption and the same enzyme systems (delta-6 desaturase and delta-5 desaturase) 2021 22. Studies show that excessive linoleic acid consumption leads to a reduced omega-3 fatty acid status 23 24. Excessive imbalance of linoleic acid to alpha-linolenic acid can impair health. A ratio of 4:1 in favor of linoleic acid, as mentioned earlier, is still within an acceptable range. However, vegans often exceed this ratio significantly since most plant-based foods contain more omega-6 than omega-3. Therefore, in general, a diet rich in omega-3 is recommended.

The consumption of linoleic acid should therefore be based on intake recommendations, as there are still too few study results available to accurately assess the adverse effects 25.

Occurrence of Linoleic Acid

High amounts of linoleic acid are found in sunflower oil (59.5 g), canola oil (18.6 g), flaxseed oil (14.3 g), as well as in Brazil nuts (23.9 g), pumpkin seeds (20.7 g), and almonds (12.3 g). Moderate use of omega-6-rich oils is recommended 26. Here is a table of other linoleic acid-containing foods.

According to Polish study results, a vegan diet significantly consumes higher proportions of linoleic acid, accounting for 6.7% of daily energy, compared to an ovo-lacto-vegetarian diet (5.5%) and a non-vegetarian diet (3.9%) 27.