Final answer:
Humans need linolenic acid because it is an essential polyunsaturated fatty acid that cannot be synthesized by the human body. It is fundamental for growth, development, and the synthesis of other important fatty acids, and it plays a role in cholesterol metabolism.
Step-by-step explanation:
Humans need linolenic acid as an essential fatty acid in their diets because the body cannot synthesize it. Linolenic acid is necessary for normal growth and development. It is used as a building block to synthesize other unsaturated fatty acids, including arachidonic acid, which is a precursor for prostaglandin synthesis and is crucial for the efficient transport and metabolism of cholesterol. Therefore, linolenic acid and linoleic acid must be obtained from dietary sources since humans cannot add double bonds in the position required to synthesize these polyunsaturated fatty acids.
Good dietary sources of linolenic acid include nuts, flaxseed, whole grains, legumes, and dark green leafy vegetables. These essential nutrients are vital in numerous biological processes, including cell membrane formation and cellular signaling. A sufficient intake is recommended to maintain overall health.