Types
Among the unsaturated fatty acids, a group of polyunsaturated fatty acids is distinguished, which contain more than one carbon-carbon double bond in the hydrocarbon chain of the acid residue. They are an essential element of the human diet (they constitute a group of the so-called vitamin F), because they are needed to create important compounds, eg prostaglandins. The most important essential fatty acids in humans are:
• linoleic acid
• α-linolenic acid
From these fatty acids, the human body can synthesize other fatty acids it needs. EFAs under the name of vitamin F (international name: vitaminum F) is used in medicine. Indications for use are, among others skin diseases.

The effects of scarcity
Deficiency in EFA:
• may cause skin diseases (dandruff)
• increases water loss in the body
• during pregnancy, it may lead to underdevelopment of the fetus

Occurrence
They occur mainly in the fats of aquatic animals and vegetable oils.

Polyunsaturated acids:
• linoleic (LA) – safflower, corn, sunflower, soybean, peanut, rapeseed oil, olive oil
• α-linolenic acid (ALA) – linseed oil, rapeseed oil, walnut oil
• γ-linolenic (GLA) – borage oil [2], evening primrose, black currant, hemp
• arachidonic (AA) – animal products, meat
• eicosapentaenoic (EPA) – algae, salmon, fish oil (cod)
• docosahexaenoic acid (DHA) – mackerel oil, some algae, flax seeds