Essential fatty acids

Biochemical characteristics

EFAs are distinguished by the position of their first double bond counting from the methyl (omega) end of the molecule. The two primary types required in human nutrition are omega‑3 and omega‑6 fatty acids. Animals lack the enzyme activities needed to introduce double bonds at those positions, so dietary intake is necessary. EFAs are often polyunsaturated and are metabolised into longer-chain derivatives used in cell membranes and for hormone‑like compounds.

Common examples and dietary sources

• Linoleic acid (an omega‑6 fatty acid) is abundant in many vegetable oils and nuts.
• Alpha‑linolenic acid (an omega‑3 fatty acid) is found in flaxseed, chia, walnuts, and some green leafy plants.
• Longer-chain omega‑3s such as EPA and DHA occur in fish and algae; these can be produced in small amounts from dietary alpha‑linolenic acid but are sometimes supplied directly by food or supplements.

History and classification

Early 20th‑century nutritional research recognised that certain dietary fats were required for normal growth and health. Initially these factors were grouped with vitamins, but later work clarified that the essential nutrients in question are fatty acids rather than vitamin compounds. For historical context on early studies and terminology see material on the role of vitamins and on the broader category of fats.

Physiological roles and clinical importance

EFAs support skin integrity, normal growth, brain development, and immune function. They are precursors to eicosanoids and other signalling molecules that influence inflammation, blood clotting and vascular tone. Deficiency is uncommon in balanced diets but can occur with very restricted fat intake, leading to dry skin, poor growth in infants, and other problems. Under some conditions—infancy, certain illnesses or genetic metabolic limitations—longer-chain polyunsaturated fatty acids become conditionally essential and may require direct dietary supply.

Practical considerations

Most health advice emphasises obtaining EFAs from whole foods such as seeds, nuts, vegetable oils, oily fish or algae-based sources. Modern diets often provide ample omega‑6 relative to omega‑3, so dietary balance and sources of omega‑3 are commonly discussed in public health guidance. Supplementation is used in specific situations but should be guided by clinical need and evidence.