Final answer:
The essential fatty acids that must be obtained through the diet are linoleic acid (an omega-6) and α-linolenic acid (omega-3). They are vital for growth, development, and maintaining various body functions, and are found in foods like oils, nuts, and green leafy vegetables.
Step-by-step explanation:
Two polyunsaturated fatty acids—linoleic and α-linolenic acids—are termed essential fatty acids because they offer vital nutrients the human body cannot synthesize and therefore must be acquired through the diet. Linoleic acid, an omega-6 fatty acid, and α-linolenic acid (ALA), an omega-3 fatty acid, are necessary for normal growth and development, including the synthesis of other unsaturated fatty acids like arachidonic acid, which is a precursor for the synthesis of prostaglandins. Additionally, essential fatty acids help with the transport and metabolism of cholesterol. Sources rich in linoleic fatty acid include corn oil and soybean oil, while sources of α-linolenic acid (ALA) include nuts, flaxseed, whole grains, legumes, and dark green leafy vegetables. The average daily diet should contain about 4–6 g of these essential fatty acids.